Publications by category
Journal articles
Vaquero-Alba I, McGowan A, Pincheira-Donoso D, Evans MR, Dall SRX (2016). A quantitative analysis of objective feather color assessment: measurements in the lab do not reflect true plumage color. Auk: a quarterly journal of ornithology, 133, 325-337.
Colman LP, Patrício ARC, McGowan A, Santos AJB, Marcovaldi MÂ, Bellini C, Godley BJ (2016). Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil.
Marine Biology,
162(1), 111-122.
Abstract:
Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil
© 2014, Springer-Verlag Berlin Heidelberg.For effective management of species of conservation concern, knowledge of life history parameters is essential. Here, we present the results of one of the longest ongoing capture-mark-recapture studies of juvenile green turtles (Chelonia mydas) worldwide. From 1988 to 2013, 1,279 individual turtles were tagged in Fernando de Noronha, Brazil (3°51′S, 32°25′W). The size distribution at first capture varied between 27 and 87 cm (mean ± SD 47.9 ± 11.3 cm) curved carapace length (CCL). Median residence time was 2.4 year (with long-term residence of up to 11.2 year), with individuals exhibiting some site fidelity within the Archipelago. Turtles at this site are slow growing (mean 2.6 ± 1.6 cm year−1; range −0.9 to 7.9 cm year−1; n = 1,022), with a non-monotonic expected growth rate function and a peak in growth rates occurring at 50–60 cm CCL. At these rates, turtles in Fernando de Noronha would need to spend ca. 22 years to grow from 30 to 87 cm CCL and even longer to reach minimum adult breeding size. A Cormack–Jolly–Seber model was used to estimate the apparent survival of the residents and recapture probabilities (2001–2012). The estimated annual abundance ranged from 420 to 1,148 individuals. Confidence around abundance estimates was low, and there was no significant trend over the period, despite steep recent increases at the major source rookery. Slow growth and stable stocking numbers may be suggestive of density-dependent regulation having taken place following initial population recovery that occurred prior to the current study.
Abstract.
Haskell PJ, McGowan A, Westling A, Méndez-Jiménez A, Rohner CA, Collins K, Rosero-Caicedo M, Salmond J, Monadjem A, Marshall AD, et al (2015). Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique.
ORYX,
49(3), 492-499.
Abstract:
Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique
The whale shark Rhincodon typus is a popular focal species in the marine tourism industry. We analysed 689 encounters with at least 142 individual sharks during 2008-2010 to assess their behaviour in the presence of swimmers at Tofo Beach, Mozambique. Sharks varied in size (estimated 3.0-9.5 m total length) and the majority (74%) were males. The sharks displayed avoidance behaviours during 64.7% of encounters. Encounter duration decreased significantly, from 12 minutes 37 s with undisturbed sharks to 8 minutes 25 s when sharks expressed avoidance behaviours, indicating that interactions with tourists affected the sharks' short-term behaviour. However, during the 2.5-year study period we found no trend in the mean encounter duration, the overall expression of avoidance behaviour or the likelihood of an individual shark exhibiting avoidance behaviours. Potential effects of tourism may be mitigated by the non-breeding status and transient behaviour of sharks at this aggregation site.
Abstract.
Hawkes LA, Mcgowan A, Broderick AC, Gore S, Wheatley D, White J, Witt MJ, Godley BJ (2014). High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands.
Ecology and Evolution,
4(8), 1255-1266.
Abstract:
High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands
Management of species of conservation concern requires knowledge of demographic parameters, such as rates of recruitment, survival, and growth. In the Caribbean, hawksbill turtles (Eretmochelys imbricata) have been historically exploited in huge numbers to satisfy trade in their shells and meat. In the present study, we estimated growth rate of juvenile hawksbill turtles around Anegada, British Virgin Islands, using capture-mark-recapture of 59 turtles over periods of up to 649 days. Turtles were recaptured up to six times, having moved up to 5.9 km from the release location. Across all sizes, turtles grew at an average rate of 9.3 cm year-1 (range 2.3-20.3 cm year-1), and gained mass at an average of 3.9 kg year-1 (range 850 g-16.1 kg year-1). Carapace length was a significant predictor of growth rate and mass gain, but there was no relationship between either variable and sea surface temperature. These are among the fastest rates of growth reported for this species, with seven turtles growing at a rate that would increase their body size by more than half per year (51-69% increase in body length). This study also demonstrates the importance of shallow water reef systems for the developmental habitat for juvenile hawksbill turtles. Although growth rates for posthatching turtles in the pelagic, and turtles larger than 61 cm, are not known for this population, the implications of this study are that Caribbean hawksbill turtles in some areas may reach body sizes suggesting sexual maturity in less time than previously considered. In the present study, we estimated growth rate of juvenile hawksbill turtles around Anegada, British Virgin Islands, using capture-mark-recapture of 59 turtles over periods of up to 649 days. Across all sizes, turtles grew at an average rate of 9.3 cm per year (range 2.3-20.3 cm year-1), and gained mass at an average of 3.9 kg year-1 (range 850 g-16.1 kg year-1). These are among the fastest rates of growth reported for this species, with seven turtles growing at a rate that would increase their body size by more than half per year (51-69% increase in body length). © 2014 the Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Abstract.
Colman LP, Patrício ARC, McGowan A, Santos AJB, Marcovaldi MÂ, Bellini C, Godley BJ (2014). Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil. Marine Biology
Haskell PJ, McGowan A, Westling A, Méndez-Jiménez A, Rohner CA, Collins K, Rosero-Caicedo M, Salmond J, Monadjem A, Marshall AD, et al (2014). Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique.
ORYXAbstract:
Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique
The whale shark Rhincodon typus is a popular focal species in the marine tourism industry. We analysed 689 encounters with at least 142 individual sharks during 2008–2010 to assess their behaviour in the presence of swimmers at Tofo Beach, Mozambique. Sharks varied in size (estimated 3.0–9.5 m total length) and the majority (74%) were males. The sharks displayed avoidance behaviours during 64.7% of encounters. Encounter duration decreased significantly, from 12 minutes 37 s with undisturbed sharks to 8 minutes 25 s when sharks expressed avoidance behaviours, indicating that interactions with tourists affected the sharks’ short-term behaviour. However, during the 2.5-year study period we found no trend in the mean encounter duration, the overall expression of avoidance behaviour or the likelihood of an individual shark exhibiting avoidance behaviours. Potential effects of tourism may be mitigated by the non-breeding status and transient behaviour of sharks at this aggregation site.
Abstract.
Napper CJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2013). Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird. Behavioral Ecology and Sociobiology, 1-11.
Napper CJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2013). Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird.
Behavioral Ecology and Sociobiology,
67(12), 2029-2039.
Abstract:
Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird
Kin selection has played an important role in the evolution and maintenance of cooperative breeding behaviour in many bird species. However, although relatedness has been shown to affect the investment decisions of helpers in such systems, less is known about the role that kin discrimination plays in other contexts, such as communal roosting. Individuals that roost communally benefit from reduced overnight heat loss, but the exact benefit derived depends on an individual's position in the roost which in turn is likely to be influenced by its position in its flock's dominance hierarchy. We studied the effects of kinship and other factors (sex, age, body size and flock sex ratio) on an individual's roosting position and dominance status in captive flocks of cooperatively breeding long-tailed tits Aegithalos caudatus. We found that overall, kinship had little influence on either variable tested; kinship had no effect on a bird's position in its flock's dominance hierarchy and the effect of kinship on roosting position was dependent on the bird's size. Males were generally dominant over females and birds were more likely to occupy preferred roosting positions if they were male, old and of high status. In this context, the effect of kinship on social interactions appears to be less important than the effects of other factors, possibly due to the complex kin structure of winter flocks compared to breeding groups. © 2013 Springer-Verlag Berlin Heidelberg.
Abstract.
Hawkes LA, McGowan A, Godley BJ, Gore S, Lange A, Tyler CR, Wheatley D, White J, Witt MJ, Broderick AC, et al (2013). Estimating sex ratios in Caribbean hawksbill turtles: Testosterone levels and climate effects.
Aquatic Biology,
18(1), 9-19.
Abstract:
Estimating sex ratios in Caribbean hawksbill turtles: Testosterone levels and climate effects
Evolutionary theory predicts that male and female offspring should be produced at a 1:1 ratio, but this may rarely be the case for species in which sex is determined during incubation by temperature, such as marine turtles. Estimates of primary sex ratio suggest that marine turtle sex ratios are highly skewed, with up to 9 females per male. We captured juvenile hawksbill turtles Eretmochelys imbricata in waters around Anegada, British Virgin Islands, a regionally important foraging aggregation, and analysed concentrations of plasma testosterone and oestradiol- 17β from 62 turtles to estimate sex ratio. There were 2.4 to 7.7 times more females than males. Testosterone concentrations correlated with sampling date and sea surface temperature (SST), with higher con centrations in the late summer when SST was highest, suggesting that assigning sex through threshold values of sex hormones must be carried out cautiously. The sex ratio in the juvenile foraging aggregation around Anegada is more male biased than at other locations, suggesting that turtles at Anegada have resilience against feminising effects of climate change. Future work should (1) integrate the relative contributions of different genetic stocks to foraging aggregations and (2) investigate the annual and seasonal cycles of sex hormones, and differences among individuals and life history stages. © Inter-Research 2013.
Abstract.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2013). No benefits of polyandry to female green turtles.
Behavioral Ecology,
24(4), 1022-1029.
Abstract:
No benefits of polyandry to female green turtles
Multiple paternity is extremely common in natural populations of almost all reptiles studied to date, suggesting that pay-offs from polyandrous mating systems are important in these taxonomic groups. However, strong evidence in support of direct or indirect benefits to females is scarce. We examined the relationship between polyandry and components of female reproductive success and offspring fitness in the promiscuous green turtle (Chelonia mydas), a species that exhibits highly variable levels of multiple paternity. We did not detect any clear fitness benefits to polyandrous females in this study, and we discuss the potential of sexual conflict to influence female mating patterns in marine turtles. We show that polyandrous females produce significantly smaller clutches than monandrous females, highlighting a potential cost to polyandry in green turtles. Furthermore, multiple paternity was more common in returning females (recorded breeding in a previous season) than in females nesting for the first time at our study site, possibly reflecting increased encounter rates with males or sperm storage across breeding seasons. Our results reveal potentially complex influences of female traits, environment, and mating strategy on components of reproductive success, and we discuss the challenges associated with unraveling the costs and benefits of multiple mating in natural populations. © 2013 the Author. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
Abstract.
Evans KL, Newton J, Gaston KJ, Sharp SP, McGowan A, Hatchwell BJ (2012). Colonisation of urban environments is associated with reduced migratory behaviour, facilitating divergence from ancestral populations.
Oikos,
121(4), 634-640.
Abstract:
Colonisation of urban environments is associated with reduced migratory behaviour, facilitating divergence from ancestral populations
How individuals colonising novel environments overcome the diverse suite of new selection pressures is a fundamental question in ecology and evolution. Urban environments differ markedly from the rural ones that they replace and successful colonisation of urban areas may therefore require local adaptation and phenotypic/genetic divergence from ancestral populations. Such a process would be facilitated by limited dispersal to and from the novel habitat. Here we assess divergence in migratory behaviour between seven pairs of urban and rural European blackbird Turdus merula populations along a 2800 km transect across Europe. This former forest specialist is now amongst the most abundant urban birds across most of its range. We use a stable isotope approach due to the lack of sufficient ringing data from multiple urban populations, and compare hydrogen isotopic ratios of tissues grown in the breeding (feathers) and wintering areas (claws) to derive an index of long distance migratory behaviour. We find a tendency for urban blackbirds to be more sedentary than rural ones at all sites and this divergence is particularly strong at the north-eastern limit of our transect, i.e. in Estonia and Latvia. These urban populations are those that have been established most recently (from the late 1930s to 1950s) implying that urbanisation can promote rapid ecological divergence. The increased sedentary behaviour of urban birds could promote further ecological divergence between rural and urban populations, such as the earlier breeding of urban blackbirds, and in some cases may contribute to their previously documented genetic divergence. © 2011 the Authors. Oikos © 2012 Nordic Society Oikos.
Abstract.
Dor R, Safran RJ, Vortman Y, Lotem A, McGowan A, Evans MR, Lovette IJ (2012). Population Genetics and Morphological Comparisons of Migratory European (Hirundo rustica rustica) and Sedentary East-Mediterranean (Hirundo rustica transitiva) Barn Swallows.
JOURNAL OF HEREDITY,
103(1), 55-63.
Author URL.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Molecular Ecology,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1 year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult. © 2012 Blackwell Publishing Ltd.
Abstract.
Wright LI, Stokes KL, Fuller WJ, Godley BJ, McGowan A, Snape R, Tregenza T, Broderick AC (2012). Turtle mating patterns buffer against disruptive effects of climate change.
Proc Biol Sci,
279(1736), 2122-2127.
Abstract:
Turtle mating patterns buffer against disruptive effects of climate change.
For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2-4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.
Abstract.
Author URL.
Dor R, Lovette IJ, Safran RJ, Billerman SM, Huber GH, Vortman Y, Lotem A, McGowan A, Evans MR, Cooper CB, et al (2011). Low variation in the polymorphic Clock gene poly-Q region despite population genetic structure across Barn Swallow (Hirundo rustica) populations.
PLoS ONE,
6(12).
Abstract:
Low variation in the polymorphic Clock gene poly-Q region despite population genetic structure across Barn Swallow (Hirundo rustica) populations
Recent studies of several species have reported a latitudinal cline in the circadian clock gene, Clock, which influences rhythms in both physiology and behavior. Latitudinal variation in this gene may hence reflect local adaptation to seasonal variation. In some bird populations, there is also an among-individual association between Clock poly-Q genotype and clutch initiation date and incubation period. We examined Clock poly-Q allele variation in the Barn Swallow (Hirundo rustica), a species with a cosmopolitan geographic distribution and considerable variation in life-history traits that may be influenced by the circadian clock. We genotyped Barn Swallows from five populations (from three subspecies) and compared variation at the Clock locus to that at microsatellite loci and mitochondrial DNA (mtDNA). We found very low variation in the Clock poly-Q region, as >96% of individuals were homozygous, and the two other alleles at this locus were globally rare. Genetic differentiation based on the Clock poly-Q locus was not correlated with genetic differentiation based on either microsatellite loci or mtDNA sequences. Our results show that high diversity in Clock poly-Q is not general across avian species. The low Clock variation in the background of heterogeneity in microsatellite and mtDNA loci in Barn Swallows may be an outcome of stabilizing selection on the Clock locus. © 2011 Dor et al.
Abstract.
Sharp SP, Simeoni M, McGowan A, Nam KB, Hatchwell BJ (2011). Patterns of recruitment, relatedness and cooperative breeding in two populations of long-tailed tits.
Animal Behaviour,
81(4), 843-849.
Abstract:
Patterns of recruitment, relatedness and cooperative breeding in two populations of long-tailed tits
Cooperative breeding has evolved primarily in species in which individuals are organized into family groups, and kin selection is considered to be a major force in the evolution of helping behaviour. Family groups are generally thought to form through delayed or limited dispersal, but dispersal patterns vary considerably both between species and in different populations of the same species, and the relationship between dispersal, kinship and cooperation is poorly understood. In this study, we combined long-term observational and genetic data to compare the patterns of demography, kinship and helping in two populations of long-tailed tits, Aegithalos caudatus, a species that exhibits kin-biased helping by failed breeders but not delayed dispersal. Both populations had the same annual breeding success, but philopatric recruitment rates were significantly higher in one population, especially for females. This led to a correspondingly higher proportion of individuals having at least one close relative in that population. Surprisingly, however, there was no difference in the pattern of helping behaviour between the two populations in terms of helper prevalence, helper sex or the relatedness between helpers and the breeders they assisted. We discuss possible explanations and highlight the limitations of population-level analyses for understanding the relationship between demography and cooperation. © 2011 the Association for the Study of Animal Behaviour.
Abstract.
Price ARG, Harris A, McGowan A, Venkatachalam AJ, Sheppard CRC (2010). Chagos feels the pinch: Assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean Territory.
Aquatic Conservation: Marine and Freshwater Ecosystems,
20(1), 117-126.
Abstract:
Chagos feels the pinch: Assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean Territory
1. Data are analysed from visual censuses of shallow-water holothurians (sea cucumbers) in 72 shallow water transects 100 m × 2m within four atolls of Chagos. Mean holothurian abundance in Diego Garcia, where harvesting is absent, was 18.5 individuals/transect (all transects) and 55.4 individuals/transect (only those containing holothurians). In the three exploited atolls, mean abundance did not exceed 3.5 and 5.2 individuals/ transect, respectively. 2. Comparison with data collected during this study and an earlier investigation reveals a marked decline over four years in both mean and maximum density of commercially valuable Stichopus chloronotus and Holothuria atra in Salomon and Peros Banhos, both exploited atolls, and also for Holothuria nobilis in the latter. 3. Holothurian counts were also made along an extensive transect (21km × 4 m) encircling Salomon atoll. Abundance showed highly significant negative correlation with fishing pressure, the latter estimated using an ordinal (0-3) scale (Rs 5 0.605, Pp0.01). Harvesting effects were not discernible using data from 200m2 transects. 4. While recent studies have shown Chagos is virtually pristine regarding contaminant levels, its holothurian resources are under increasing pressure. Results from this study, and examination of Sri Lanka's fishing activity in distant waters, point to heavy and illegal harvesting. 5. Stronger measures are needed to control the illegal fishery, to prevent holothurian abundances falling to the nonsustainable levels now prevalent across much of the Indo-Pacific, and to ensure that Chagos remains a biodiversity hotspot and environment of international renown. Use of smaller surveillance vessels would facilitate this. © 2009 John Wiley & Sons, Ltd.
Abstract.
Witt MJ, McGowan A, Blumenthal JM, Broderick AC, Gore S, Wheatley D, White J, Godley BJ (2010). Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders.
AQUATIC BIOLOGY,
8(2), 169-177.
Author URL.
Campbell LM, Silver JJ, Gray NJ, Ranger S, Broderick AC, Fisher T, Godfrey MH, Gore S, Hodge KVD, Jeffers J, et al (2009). Co-management of sea turtle fisheries: Biogeography versus geopolitics. Marine Policy, 33, 137-145.
Evans KL, Gaston KJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2009). Effects of urbanisation on disease prevalence and age structure in blackbird Turdus merula populations.
Oikos,
118(5), 774-782.
Abstract:
Effects of urbanisation on disease prevalence and age structure in blackbird Turdus merula populations
Despite increasing interest in urban ecology most attention has focussed on describing changes in assemblage composition and structure along urbanisation gradients, whilst relatively little research has focussed on the mechanisms behind these changes. Ecological theory predicts that alterations in biotic interactions are particularly likely to arise, especially with regard to disease risk. Here, we report on differences in prevalence of avian malaria and tick infection and intensity in 11 paired urban and rural blackbird Turdus merula populations from across the western Palearctic. We find large and consistent reductions in tick prevalence and intensity in urban areas. There are also large reductions in the prevalence of avian malaria in many, but not all, urban areas. The proportion of first year birds in urban populations is significantly lower than that in rural ones, and across the more natural rural sites southerly populations contain fewer first years than northern ones. These patterns are expected to arise if survival rates are higher in urban areas, and are negatively correlated with latitude. © 2009 Oikos.
Abstract.
Hatchwell BJ, Sharp SP, Simeoni M, McGowan A (2009). Factors influencing overnight loss of body mass in the communal roosts of a social bird.
Functional Ecology,
23(2), 367-372.
Abstract:
Factors influencing overnight loss of body mass in the communal roosts of a social bird
Communal roosting behaviour in birds is hypothesized to reduce the risk of starvation by lowering the energetic expenditure required to survive the night. However, the metabolic benefit gained is likely to depend on various factors, including an individual's position within the roost. 2. The long-tailed tit Aegithalos caudatus L. is a social species that lives in flocks during the non-breeding season, forming linear roosting huddles in which individuals compete to avoid occupying the peripheral positions at either end of the roost. Using observations of 18 temporarily captive flocks of long-tailed tits, we examine the effects of position and other factors on the mass lost during roosting. 3. We found that, on average, long-tailed tits lost about 9% of their body mass overnight, and that individuals occupying the peripheral positions in a roost lost significantly more mass than those occupying inner positions. 4. Overnight mass loss was related to minimum temperature, being greatest at 4 °C and decreasing at higher and lower temperatures. This result suggests that long-tailed tits may use facultative nocturnal hypothermia to reduce energetic costs at low ambient temperature. Mass loss also tended to increase with group size, perhaps because of the greater competition for inner positions in larger flocks, although we have no direct evidence for this. Mass loss was also positively correlated with mass when going to roost, and males lost marginally more mass than females. 5. There was no evidence that individuals strategically adjusted their daily mass when going to roost in relation to their likely roosting position even though outer positions are consistently and therefore predictably occupied by the same individuals on successive nights. 6. We conclude that long-tailed tits mitigate the costs of surviving the night by roosting communally, but the benefits gained vary in relation to position within the roost, explaining previous observations of competitive interactions during roost formation. 7. The benefit derived from communal behaviour is likely to vary among individuals and the degree of conflict over these benefits is likely to depend on both intrinsic and extrinsic factors. © 2008 British Ecological Society.
Abstract.
Pintus KJ, Godley BJ, McGowan A, Broderick AC (2009). Impact of clutch relocation on green turtle offspring.
Journal of Wildlife Management,
73(7), 1151-1157.
Abstract:
Impact of clutch relocation on green turtle offspring
For species with temperature-dependent sex determination, such as marine turtles, global climate change poses numerous threats. At the nesting beach, rising temperatures are predicted to further skew already female-biased sex ratios and increase embryonic mortality; sea-level rise and resultant coastal squeeze may leave few alternative breeding habitats in developed regions. As a result, clutch relocation, a commonly used management tool to reduce egg loss, may become necessary for safeguarding populations. Although studies have examined the impact of relocation on clutch success, few have examined the impact of this practice on the sex or phenotypic characteristics of hatchlings produced. We used a randomized block design experiment to examine effects of relocation on green turtle (Chelonia mydas) clutches. We compared hatching success, thermal conditions, and size (length and mass) of hatchlings from in situ control clutches with those subjected to 2 relocation methods, while controlling for maternal and other environmental effects. Relocated clutches did not vary significantly from control clutches in incubation temperature or inferred sex ratios during the critical middle third of incubation when sex is thought to be determined. Hatchling size was also unaffected by relocation. Both relocation methods, however, resulted in a 20 reduction in hatching success in comparison to in situ clutches. Clutch relocation is, however, likely to affect the population primary sex ratio, when clutches are relocated from sites in proximity to the sea where tidal inundation is a threat. Here, cooler conditions are likely to produce more males than are the warmer female-producing temperatures higher up the beach. For clutches at risk, relocation is a viable process and does not appear to affect hatchling size or predicted sex ratios if relocation sites are selected in areas utilized by other females. We urge caution, however, when moving clutches from potentially male-producing sites, particularly given predicted impacts of climate change on already female-biased sex ratios. © 2009 the Wildlife Society.
Abstract.
Evans KL, Gaston KJ, Frantz AC, Simeoni M, Sharp SP, McGowan A, Dawson DA, Walasz K, Partecke J, Burke T, et al (2009). Independent colonization of multiple urban centres by a formerly forest specialist bird species.
Proc Biol Sci,
276(1666), 2403-2410.
Abstract:
Independent colonization of multiple urban centres by a formerly forest specialist bird species.
Urban areas are expanding rapidly, but a few native species have successfully colonized them. The processes underlying such colonization events are poorly understood. Using the blackbird Turdus merula, a former forest specialist that is now one of the most common urban birds in its range, we provide the first assessment of two contrasting urban colonization models. First, that urbanization occurred independently. Second, that following initial urbanization, urban-adapted individuals colonized other urban areas in a leapfrog manner. Previous analyses of spatial patterns in the timing of blackbird urbanization, and experimental introductions of urban and rural blackbirds to uncolonized cities, suggest that the leapfrog model is likely to apply. We found that, across the western Palaearctic, urban blackbird populations contain less genetic diversity than rural ones, urban populations are more strongly differentiated from each other than from rural populations and assignment tests support a rural source population for most urban individuals. In combination, these results provide much stronger support for the independent urbanization model than the leapfrog one. If the former model predominates, colonization of multiple urban centres will be particularly difficult when urbanization requires genetic adaptations, having implications for urban species diversity.
Abstract.
Author URL.
Evans KL, Gaston KJ, Sharp SP, McGowan A, Hatchwell BJ (2009). The effect of urbanisation on avian morphology and latitudinal gradients in body size.
Oikos,
118(2), 251-259.
Abstract:
The effect of urbanisation on avian morphology and latitudinal gradients in body size
Urban areas occupy a large and growing proportion of the earth. Such sites exhibit distinctive characteristics relative to adjacent rural habitats, and many species have colonised and now successfully exploit urban habitats. The change in selection pressures as a result of urbanisation has led to trait divergence in some urban populations relative to their rural counterparts, but studies have generally been local in scale and the generality of differentiation thus remains unknown. The European blackbird Turdus merula is one of the commonest urban bird species in the Western Palearctic, but populations vary substantially in the length of time they have been urbanised. Here we investigate patterns of morphological variation in European blackbirds occupying 11 paired urban and rural habitats across much of the urbanised range of this species and spanning 25° of latitude. First, we assessed the extent to which urban and rural blackbirds are differentiated morphologically and the consistency of any differentiation across the range. Paired urban and rural Blackbird populations frequently exhibited significant morphological differences, but the magnitude and direction of differentiation was site dependent. We then investigated whether the nature of latitudinal gradients in body-size differed between urban and rural populations, as predicted by differences in the climatic regimes of urban and rural areas. Blackbird body-size exhibited strong latitudinal gradients, but their form did not differ significantly between urban and rural habitats. The latitudinal gradient in body size may be a consequence of Seebohm's rule, that more migratory populations occurring at high latitudes have longer wings. We conclude that while there can be substantial morphological variation between adjacent urban and rural bird populations, such differentiation may not apply across a species' range. Locality specific differentiation of urban and rural blackbirds may arise if the selection pressures acting on blackbird morphology vary in an inconsistent manner between urban and rural habitats. Alternatively, phenotypic divergence could arise in a stochastic manner depending on the morphological traits of colonists, through founder effects. © 2009 the Authors.
Abstract.
Broderick, A.C. Frett, G. Gore, S. (2008). Down But Not Out: Marine Turtles of the British Virgin Islands. Animal Conservation
Gan C-H, Tee S-M, Tang P-C, Yang JM-C, Freire F, McGowan A, Narriman J, Mohammed MS, Hsieh H-L, Chen C-P, et al (2008). Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro).
Mol Ecol Resour,
8(6), 1448-1450.
Abstract:
Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro).
The coconut crab (Birgus latro), an endangered marine-dispersed crustacean, is facing severe and probably accelerating population extinction worldwide, but biological information on its conservation remains deficient. In order to reveal the genetic structure of B. latro, 10 microsatellite loci were developed. A high degree of polymorphism was observed with a mean number of alleles per locus of 16.9. The mean expected heterozygosities were also high, ranging from 0.742 to 0.965. The observed heterozygosities ranged from 0.210 to 0.925. Departures from Hardy-Weinberg equilibrium were observed at five loci after the Bonferroni correction. These hypervariable markers will be utilized to study the genetic diversity and conservation of B. latro throughout its distribution range in the Pacific and Indian Oceans.
Abstract.
Author URL.
Mcgowan A, Broderick, A.C. Godley, B.J. (2008). Seabird populations of the Chagos Archipelago: an evaluation of IBA sites and a need for monitoring. Oryx
McGowan A, Woodfield NK, Hilton G, Broderick AC, Godley BJ (2007). A rigorous assessment of the Avifauna of a small Caribbean Island: a case study in Anegada, British Virgin Islands.
Caribbean Journal of Science,
43(1), 99-116.
Abstract:
A rigorous assessment of the Avifauna of a small Caribbean Island: a case study in Anegada, British Virgin Islands
The avifauna of the British Virgin Islands (BVI) has received little attention from researchers. The lack of baseline information is therefore a major hindrance to the construction of management plans. Here we present detailed monitoring data on the species composition and numbers of each-species for the island of Anegada, BVI. We surveyed the birds of Anegada between November 2003 and March 2005 utilising a combination of coastal transects, wetland bird counts, point counts, and species-specific survey methods for nocturnal species. A total of 99 different species were recorded, with a large increase in the number of species and number of individuals centred around peak migration in September. Although there is a depauperate terrestrial bird community consisting of predominately generalist species, it holds important populations of regional avifauna. For example, it hosts five regionally important breeding seabird colonies and its wetlands provide an important stop-over and over-wintering site for many species of shorebirds and waterbirds. In addition, the Eastern salt ponds are also the only breeding site for the greater flamingo, Phoenicopterus ruber, within the territory. We discuss our findings within the current framework of regional conservation and provide recommendations for the implementation of a territory wide monitoring program as a first step towards meeting the UK's commitments under several multilateral environmental agreements. Copyright 2007 College of Arts and Science.
Abstract.
McGowan A, Wright LI, Hunt J (2007). Inbreeding and population dynamics: implications for conservation strategies. Animal Conservation, 10, 284-285.
Mcgowan A, Fowlie MK, Ross DJ, Hatchwell BJ (2007). Social organization of co-operatively breeding Long-tailed Tits Aegithalos caudatus: Flock composition and kinship. Ibis, 149(1), 170-174.
Broderick, A.C. Gore, S. Hilton, G. (2006). Breeding seabirds in the British Virgin Islands.
Endangered Species Research,
3, 1-6.
Author URL.
McGowan A, Sharp SP, Simeoni M & Hatchwell BJ (2006). Competing for position in the communal roosts of long-tailed tits. Animal Behaviour, 76, 1035-1043.
Sharp SP, McGowan A, Wood MJ & Hatchwell BJ (2005). Learned kin recognition cues in a social bird. Nature, 434, 1127-1130.
Dickinson JL & McGowan A (2005). Winter resource wealth drives delayed dispersal and family-group living in western bluebirds. Proceedings of the Royal Society B, 272, 2423-2428.
Hatchwell BJ, Russell AF, MacColl ADC, Ross DJ, Fowlie MK, McGowan A (2004). Helpers increase long-term but not short-term productivity in cooperatively breeding long-tailed tits. Behavioral Ecology, 15, 1-10.
McGowan A, Sharp SP & Hatchwell BJ (2004). The structure and function of nests of long-tailed tits <em>Aegithalos caudatus</em>. Functional Ecology, 18, 578-583.
McGowan A, Hatchwell BJ & Woodburn RJW (2003). The effect of helping behaviour on the survival of juvenile and adult long-tailed tits (<em>Aegithalo caudatus</em>). Journal of Animal Ecology, 72, 491-499.
McGowan A, Cresswell W & Ruxton GD (2002). The effects of daily weather variation on foraging and responsiveness to disturbance in over-wintering Red Knot (<em>Calidris canutus</em>). Ardea, 90, 229-237.
Broderick, A.C. Deeming, J. Godley, B.J. (2001). Dipteran infestation of loggerhead (Caretta caretta), and green (Chelonia mydas), sea turtle nests in northern Cyprus. Journal of natural History, 35, 573-581.
Hatchwell BJ, Ross DJ, Fowlie MK & McGowan A (2001). Kin discrimination in cooperatively breeding long-tailed tits. Proceedings of the Royal Society B, 268, 885-890.
McGowan A, Rowe, L.V. Broderick, A.C. Godley, B.J. (2001). Nest factors predisposing loggerhead sea turtle (Caretta caretta) clutches to infestation by dipteran larvae on northern Cyprus. Copeia, 2001(3), 808-812.
Reports
Broderick AC, Godley BJ, Kelly a & McGowan A (1997). Glasgow University Turtle Conservation Expedition 1997: Expedition Report. Marine Turtle Research Group, Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow.
Publications by year
2016
Vaquero-Alba I, McGowan A, Pincheira-Donoso D, Evans MR, Dall SRX (2016). A quantitative analysis of objective feather color assessment: measurements in the lab do not reflect true plumage color. Auk: a quarterly journal of ornithology, 133, 325-337.
Colman LP, Patrício ARC, McGowan A, Santos AJB, Marcovaldi MÂ, Bellini C, Godley BJ (2016). Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil.
Marine Biology,
162(1), 111-122.
Abstract:
Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil
© 2014, Springer-Verlag Berlin Heidelberg.For effective management of species of conservation concern, knowledge of life history parameters is essential. Here, we present the results of one of the longest ongoing capture-mark-recapture studies of juvenile green turtles (Chelonia mydas) worldwide. From 1988 to 2013, 1,279 individual turtles were tagged in Fernando de Noronha, Brazil (3°51′S, 32°25′W). The size distribution at first capture varied between 27 and 87 cm (mean ± SD 47.9 ± 11.3 cm) curved carapace length (CCL). Median residence time was 2.4 year (with long-term residence of up to 11.2 year), with individuals exhibiting some site fidelity within the Archipelago. Turtles at this site are slow growing (mean 2.6 ± 1.6 cm year−1; range −0.9 to 7.9 cm year−1; n = 1,022), with a non-monotonic expected growth rate function and a peak in growth rates occurring at 50–60 cm CCL. At these rates, turtles in Fernando de Noronha would need to spend ca. 22 years to grow from 30 to 87 cm CCL and even longer to reach minimum adult breeding size. A Cormack–Jolly–Seber model was used to estimate the apparent survival of the residents and recapture probabilities (2001–2012). The estimated annual abundance ranged from 420 to 1,148 individuals. Confidence around abundance estimates was low, and there was no significant trend over the period, despite steep recent increases at the major source rookery. Slow growth and stable stocking numbers may be suggestive of density-dependent regulation having taken place following initial population recovery that occurred prior to the current study.
Abstract.
2015
Haskell PJ, McGowan A, Westling A, Méndez-Jiménez A, Rohner CA, Collins K, Rosero-Caicedo M, Salmond J, Monadjem A, Marshall AD, et al (2015). Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique.
ORYX,
49(3), 492-499.
Abstract:
Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique
The whale shark Rhincodon typus is a popular focal species in the marine tourism industry. We analysed 689 encounters with at least 142 individual sharks during 2008-2010 to assess their behaviour in the presence of swimmers at Tofo Beach, Mozambique. Sharks varied in size (estimated 3.0-9.5 m total length) and the majority (74%) were males. The sharks displayed avoidance behaviours during 64.7% of encounters. Encounter duration decreased significantly, from 12 minutes 37 s with undisturbed sharks to 8 minutes 25 s when sharks expressed avoidance behaviours, indicating that interactions with tourists affected the sharks' short-term behaviour. However, during the 2.5-year study period we found no trend in the mean encounter duration, the overall expression of avoidance behaviour or the likelihood of an individual shark exhibiting avoidance behaviours. Potential effects of tourism may be mitigated by the non-breeding status and transient behaviour of sharks at this aggregation site.
Abstract.
2014
Hawkes LA, Mcgowan A, Broderick AC, Gore S, Wheatley D, White J, Witt MJ, Godley BJ (2014). High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands.
Ecology and Evolution,
4(8), 1255-1266.
Abstract:
High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands
Management of species of conservation concern requires knowledge of demographic parameters, such as rates of recruitment, survival, and growth. In the Caribbean, hawksbill turtles (Eretmochelys imbricata) have been historically exploited in huge numbers to satisfy trade in their shells and meat. In the present study, we estimated growth rate of juvenile hawksbill turtles around Anegada, British Virgin Islands, using capture-mark-recapture of 59 turtles over periods of up to 649 days. Turtles were recaptured up to six times, having moved up to 5.9 km from the release location. Across all sizes, turtles grew at an average rate of 9.3 cm year-1 (range 2.3-20.3 cm year-1), and gained mass at an average of 3.9 kg year-1 (range 850 g-16.1 kg year-1). Carapace length was a significant predictor of growth rate and mass gain, but there was no relationship between either variable and sea surface temperature. These are among the fastest rates of growth reported for this species, with seven turtles growing at a rate that would increase their body size by more than half per year (51-69% increase in body length). This study also demonstrates the importance of shallow water reef systems for the developmental habitat for juvenile hawksbill turtles. Although growth rates for posthatching turtles in the pelagic, and turtles larger than 61 cm, are not known for this population, the implications of this study are that Caribbean hawksbill turtles in some areas may reach body sizes suggesting sexual maturity in less time than previously considered. In the present study, we estimated growth rate of juvenile hawksbill turtles around Anegada, British Virgin Islands, using capture-mark-recapture of 59 turtles over periods of up to 649 days. Across all sizes, turtles grew at an average rate of 9.3 cm per year (range 2.3-20.3 cm year-1), and gained mass at an average of 3.9 kg year-1 (range 850 g-16.1 kg year-1). These are among the fastest rates of growth reported for this species, with seven turtles growing at a rate that would increase their body size by more than half per year (51-69% increase in body length). © 2014 the Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Abstract.
Colman LP, Patrício ARC, McGowan A, Santos AJB, Marcovaldi MÂ, Bellini C, Godley BJ (2014). Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil. Marine Biology
Haskell PJ, McGowan A, Westling A, Méndez-Jiménez A, Rohner CA, Collins K, Rosero-Caicedo M, Salmond J, Monadjem A, Marshall AD, et al (2014). Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique.
ORYXAbstract:
Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique
The whale shark Rhincodon typus is a popular focal species in the marine tourism industry. We analysed 689 encounters with at least 142 individual sharks during 2008–2010 to assess their behaviour in the presence of swimmers at Tofo Beach, Mozambique. Sharks varied in size (estimated 3.0–9.5 m total length) and the majority (74%) were males. The sharks displayed avoidance behaviours during 64.7% of encounters. Encounter duration decreased significantly, from 12 minutes 37 s with undisturbed sharks to 8 minutes 25 s when sharks expressed avoidance behaviours, indicating that interactions with tourists affected the sharks’ short-term behaviour. However, during the 2.5-year study period we found no trend in the mean encounter duration, the overall expression of avoidance behaviour or the likelihood of an individual shark exhibiting avoidance behaviours. Potential effects of tourism may be mitigated by the non-breeding status and transient behaviour of sharks at this aggregation site.
Abstract.
2013
Napper CJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2013). Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird. Behavioral Ecology and Sociobiology, 1-11.
Napper CJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2013). Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird.
Behavioral Ecology and Sociobiology,
67(12), 2029-2039.
Abstract:
Dominance, not kinship, determines individual position within the communal roosts of a cooperatively breeding bird
Kin selection has played an important role in the evolution and maintenance of cooperative breeding behaviour in many bird species. However, although relatedness has been shown to affect the investment decisions of helpers in such systems, less is known about the role that kin discrimination plays in other contexts, such as communal roosting. Individuals that roost communally benefit from reduced overnight heat loss, but the exact benefit derived depends on an individual's position in the roost which in turn is likely to be influenced by its position in its flock's dominance hierarchy. We studied the effects of kinship and other factors (sex, age, body size and flock sex ratio) on an individual's roosting position and dominance status in captive flocks of cooperatively breeding long-tailed tits Aegithalos caudatus. We found that overall, kinship had little influence on either variable tested; kinship had no effect on a bird's position in its flock's dominance hierarchy and the effect of kinship on roosting position was dependent on the bird's size. Males were generally dominant over females and birds were more likely to occupy preferred roosting positions if they were male, old and of high status. In this context, the effect of kinship on social interactions appears to be less important than the effects of other factors, possibly due to the complex kin structure of winter flocks compared to breeding groups. © 2013 Springer-Verlag Berlin Heidelberg.
Abstract.
Hawkes LA, McGowan A, Godley BJ, Gore S, Lange A, Tyler CR, Wheatley D, White J, Witt MJ, Broderick AC, et al (2013). Estimating sex ratios in Caribbean hawksbill turtles: Testosterone levels and climate effects.
Aquatic Biology,
18(1), 9-19.
Abstract:
Estimating sex ratios in Caribbean hawksbill turtles: Testosterone levels and climate effects
Evolutionary theory predicts that male and female offspring should be produced at a 1:1 ratio, but this may rarely be the case for species in which sex is determined during incubation by temperature, such as marine turtles. Estimates of primary sex ratio suggest that marine turtle sex ratios are highly skewed, with up to 9 females per male. We captured juvenile hawksbill turtles Eretmochelys imbricata in waters around Anegada, British Virgin Islands, a regionally important foraging aggregation, and analysed concentrations of plasma testosterone and oestradiol- 17β from 62 turtles to estimate sex ratio. There were 2.4 to 7.7 times more females than males. Testosterone concentrations correlated with sampling date and sea surface temperature (SST), with higher con centrations in the late summer when SST was highest, suggesting that assigning sex through threshold values of sex hormones must be carried out cautiously. The sex ratio in the juvenile foraging aggregation around Anegada is more male biased than at other locations, suggesting that turtles at Anegada have resilience against feminising effects of climate change. Future work should (1) integrate the relative contributions of different genetic stocks to foraging aggregations and (2) investigate the annual and seasonal cycles of sex hormones, and differences among individuals and life history stages. © Inter-Research 2013.
Abstract.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2013). No benefits of polyandry to female green turtles.
Behavioral Ecology,
24(4), 1022-1029.
Abstract:
No benefits of polyandry to female green turtles
Multiple paternity is extremely common in natural populations of almost all reptiles studied to date, suggesting that pay-offs from polyandrous mating systems are important in these taxonomic groups. However, strong evidence in support of direct or indirect benefits to females is scarce. We examined the relationship between polyandry and components of female reproductive success and offspring fitness in the promiscuous green turtle (Chelonia mydas), a species that exhibits highly variable levels of multiple paternity. We did not detect any clear fitness benefits to polyandrous females in this study, and we discuss the potential of sexual conflict to influence female mating patterns in marine turtles. We show that polyandrous females produce significantly smaller clutches than monandrous females, highlighting a potential cost to polyandry in green turtles. Furthermore, multiple paternity was more common in returning females (recorded breeding in a previous season) than in females nesting for the first time at our study site, possibly reflecting increased encounter rates with males or sperm storage across breeding seasons. Our results reveal potentially complex influences of female traits, environment, and mating strategy on components of reproductive success, and we discuss the challenges associated with unraveling the costs and benefits of multiple mating in natural populations. © 2013 the Author. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.
Abstract.
2012
Evans KL, Newton J, Gaston KJ, Sharp SP, McGowan A, Hatchwell BJ (2012). Colonisation of urban environments is associated with reduced migratory behaviour, facilitating divergence from ancestral populations.
Oikos,
121(4), 634-640.
Abstract:
Colonisation of urban environments is associated with reduced migratory behaviour, facilitating divergence from ancestral populations
How individuals colonising novel environments overcome the diverse suite of new selection pressures is a fundamental question in ecology and evolution. Urban environments differ markedly from the rural ones that they replace and successful colonisation of urban areas may therefore require local adaptation and phenotypic/genetic divergence from ancestral populations. Such a process would be facilitated by limited dispersal to and from the novel habitat. Here we assess divergence in migratory behaviour between seven pairs of urban and rural European blackbird Turdus merula populations along a 2800 km transect across Europe. This former forest specialist is now amongst the most abundant urban birds across most of its range. We use a stable isotope approach due to the lack of sufficient ringing data from multiple urban populations, and compare hydrogen isotopic ratios of tissues grown in the breeding (feathers) and wintering areas (claws) to derive an index of long distance migratory behaviour. We find a tendency for urban blackbirds to be more sedentary than rural ones at all sites and this divergence is particularly strong at the north-eastern limit of our transect, i.e. in Estonia and Latvia. These urban populations are those that have been established most recently (from the late 1930s to 1950s) implying that urbanisation can promote rapid ecological divergence. The increased sedentary behaviour of urban birds could promote further ecological divergence between rural and urban populations, such as the earlier breeding of urban blackbirds, and in some cases may contribute to their previously documented genetic divergence. © 2011 the Authors. Oikos © 2012 Nordic Society Oikos.
Abstract.
Dor R, Safran RJ, Vortman Y, Lotem A, McGowan A, Evans MR, Lovette IJ (2012). Population Genetics and Morphological Comparisons of Migratory European (Hirundo rustica rustica) and Sedentary East-Mediterranean (Hirundo rustica transitiva) Barn Swallows.
JOURNAL OF HEREDITY,
103(1), 55-63.
Author URL.
Wright LI, Fuller WJ, Godley BJ, McGowan A, Tregenza T, Broderick AC (2012). Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually.
Molecular Ecology,
21(14), 3625-3635.
Abstract:
Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1 year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult. © 2012 Blackwell Publishing Ltd.
Abstract.
Wright LI, Stokes KL, Fuller WJ, Godley BJ, McGowan A, Snape R, Tregenza T, Broderick AC (2012). Turtle mating patterns buffer against disruptive effects of climate change.
Proc Biol Sci,
279(1736), 2122-2127.
Abstract:
Turtle mating patterns buffer against disruptive effects of climate change.
For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2-4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.
Abstract.
Author URL.
2011
Dor R, Lovette IJ, Safran RJ, Billerman SM, Huber GH, Vortman Y, Lotem A, McGowan A, Evans MR, Cooper CB, et al (2011). Low variation in the polymorphic Clock gene poly-Q region despite population genetic structure across Barn Swallow (Hirundo rustica) populations.
PLoS ONE,
6(12).
Abstract:
Low variation in the polymorphic Clock gene poly-Q region despite population genetic structure across Barn Swallow (Hirundo rustica) populations
Recent studies of several species have reported a latitudinal cline in the circadian clock gene, Clock, which influences rhythms in both physiology and behavior. Latitudinal variation in this gene may hence reflect local adaptation to seasonal variation. In some bird populations, there is also an among-individual association between Clock poly-Q genotype and clutch initiation date and incubation period. We examined Clock poly-Q allele variation in the Barn Swallow (Hirundo rustica), a species with a cosmopolitan geographic distribution and considerable variation in life-history traits that may be influenced by the circadian clock. We genotyped Barn Swallows from five populations (from three subspecies) and compared variation at the Clock locus to that at microsatellite loci and mitochondrial DNA (mtDNA). We found very low variation in the Clock poly-Q region, as >96% of individuals were homozygous, and the two other alleles at this locus were globally rare. Genetic differentiation based on the Clock poly-Q locus was not correlated with genetic differentiation based on either microsatellite loci or mtDNA sequences. Our results show that high diversity in Clock poly-Q is not general across avian species. The low Clock variation in the background of heterogeneity in microsatellite and mtDNA loci in Barn Swallows may be an outcome of stabilizing selection on the Clock locus. © 2011 Dor et al.
Abstract.
Sharp SP, Simeoni M, McGowan A, Nam KB, Hatchwell BJ (2011). Patterns of recruitment, relatedness and cooperative breeding in two populations of long-tailed tits.
Animal Behaviour,
81(4), 843-849.
Abstract:
Patterns of recruitment, relatedness and cooperative breeding in two populations of long-tailed tits
Cooperative breeding has evolved primarily in species in which individuals are organized into family groups, and kin selection is considered to be a major force in the evolution of helping behaviour. Family groups are generally thought to form through delayed or limited dispersal, but dispersal patterns vary considerably both between species and in different populations of the same species, and the relationship between dispersal, kinship and cooperation is poorly understood. In this study, we combined long-term observational and genetic data to compare the patterns of demography, kinship and helping in two populations of long-tailed tits, Aegithalos caudatus, a species that exhibits kin-biased helping by failed breeders but not delayed dispersal. Both populations had the same annual breeding success, but philopatric recruitment rates were significantly higher in one population, especially for females. This led to a correspondingly higher proportion of individuals having at least one close relative in that population. Surprisingly, however, there was no difference in the pattern of helping behaviour between the two populations in terms of helper prevalence, helper sex or the relatedness between helpers and the breeders they assisted. We discuss possible explanations and highlight the limitations of population-level analyses for understanding the relationship between demography and cooperation. © 2011 the Association for the Study of Animal Behaviour.
Abstract.
2010
Price ARG, Harris A, McGowan A, Venkatachalam AJ, Sheppard CRC (2010). Chagos feels the pinch: Assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean Territory.
Aquatic Conservation: Marine and Freshwater Ecosystems,
20(1), 117-126.
Abstract:
Chagos feels the pinch: Assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean Territory
1. Data are analysed from visual censuses of shallow-water holothurians (sea cucumbers) in 72 shallow water transects 100 m × 2m within four atolls of Chagos. Mean holothurian abundance in Diego Garcia, where harvesting is absent, was 18.5 individuals/transect (all transects) and 55.4 individuals/transect (only those containing holothurians). In the three exploited atolls, mean abundance did not exceed 3.5 and 5.2 individuals/ transect, respectively. 2. Comparison with data collected during this study and an earlier investigation reveals a marked decline over four years in both mean and maximum density of commercially valuable Stichopus chloronotus and Holothuria atra in Salomon and Peros Banhos, both exploited atolls, and also for Holothuria nobilis in the latter. 3. Holothurian counts were also made along an extensive transect (21km × 4 m) encircling Salomon atoll. Abundance showed highly significant negative correlation with fishing pressure, the latter estimated using an ordinal (0-3) scale (Rs 5 0.605, Pp0.01). Harvesting effects were not discernible using data from 200m2 transects. 4. While recent studies have shown Chagos is virtually pristine regarding contaminant levels, its holothurian resources are under increasing pressure. Results from this study, and examination of Sri Lanka's fishing activity in distant waters, point to heavy and illegal harvesting. 5. Stronger measures are needed to control the illegal fishery, to prevent holothurian abundances falling to the nonsustainable levels now prevalent across much of the Indo-Pacific, and to ensure that Chagos remains a biodiversity hotspot and environment of international renown. Use of smaller surveillance vessels would facilitate this. © 2009 John Wiley & Sons, Ltd.
Abstract.
Witt MJ, McGowan A, Blumenthal JM, Broderick AC, Gore S, Wheatley D, White J, Godley BJ (2010). Inferring vertical and horizontal movements of juvenile marine turtles from time-depth recorders.
AQUATIC BIOLOGY,
8(2), 169-177.
Author URL.
2009
Campbell LM, Silver JJ, Gray NJ, Ranger S, Broderick AC, Fisher T, Godfrey MH, Gore S, Hodge KVD, Jeffers J, et al (2009). Co-management of sea turtle fisheries: Biogeography versus geopolitics. Marine Policy, 33, 137-145.
Evans KL, Gaston KJ, Sharp SP, McGowan A, Simeoni M, Hatchwell BJ (2009). Effects of urbanisation on disease prevalence and age structure in blackbird Turdus merula populations.
Oikos,
118(5), 774-782.
Abstract:
Effects of urbanisation on disease prevalence and age structure in blackbird Turdus merula populations
Despite increasing interest in urban ecology most attention has focussed on describing changes in assemblage composition and structure along urbanisation gradients, whilst relatively little research has focussed on the mechanisms behind these changes. Ecological theory predicts that alterations in biotic interactions are particularly likely to arise, especially with regard to disease risk. Here, we report on differences in prevalence of avian malaria and tick infection and intensity in 11 paired urban and rural blackbird Turdus merula populations from across the western Palearctic. We find large and consistent reductions in tick prevalence and intensity in urban areas. There are also large reductions in the prevalence of avian malaria in many, but not all, urban areas. The proportion of first year birds in urban populations is significantly lower than that in rural ones, and across the more natural rural sites southerly populations contain fewer first years than northern ones. These patterns are expected to arise if survival rates are higher in urban areas, and are negatively correlated with latitude. © 2009 Oikos.
Abstract.
Hatchwell BJ, Sharp SP, Simeoni M, McGowan A (2009). Factors influencing overnight loss of body mass in the communal roosts of a social bird.
Functional Ecology,
23(2), 367-372.
Abstract:
Factors influencing overnight loss of body mass in the communal roosts of a social bird
Communal roosting behaviour in birds is hypothesized to reduce the risk of starvation by lowering the energetic expenditure required to survive the night. However, the metabolic benefit gained is likely to depend on various factors, including an individual's position within the roost. 2. The long-tailed tit Aegithalos caudatus L. is a social species that lives in flocks during the non-breeding season, forming linear roosting huddles in which individuals compete to avoid occupying the peripheral positions at either end of the roost. Using observations of 18 temporarily captive flocks of long-tailed tits, we examine the effects of position and other factors on the mass lost during roosting. 3. We found that, on average, long-tailed tits lost about 9% of their body mass overnight, and that individuals occupying the peripheral positions in a roost lost significantly more mass than those occupying inner positions. 4. Overnight mass loss was related to minimum temperature, being greatest at 4 °C and decreasing at higher and lower temperatures. This result suggests that long-tailed tits may use facultative nocturnal hypothermia to reduce energetic costs at low ambient temperature. Mass loss also tended to increase with group size, perhaps because of the greater competition for inner positions in larger flocks, although we have no direct evidence for this. Mass loss was also positively correlated with mass when going to roost, and males lost marginally more mass than females. 5. There was no evidence that individuals strategically adjusted their daily mass when going to roost in relation to their likely roosting position even though outer positions are consistently and therefore predictably occupied by the same individuals on successive nights. 6. We conclude that long-tailed tits mitigate the costs of surviving the night by roosting communally, but the benefits gained vary in relation to position within the roost, explaining previous observations of competitive interactions during roost formation. 7. The benefit derived from communal behaviour is likely to vary among individuals and the degree of conflict over these benefits is likely to depend on both intrinsic and extrinsic factors. © 2008 British Ecological Society.
Abstract.
Pintus KJ, Godley BJ, McGowan A, Broderick AC (2009). Impact of clutch relocation on green turtle offspring.
Journal of Wildlife Management,
73(7), 1151-1157.
Abstract:
Impact of clutch relocation on green turtle offspring
For species with temperature-dependent sex determination, such as marine turtles, global climate change poses numerous threats. At the nesting beach, rising temperatures are predicted to further skew already female-biased sex ratios and increase embryonic mortality; sea-level rise and resultant coastal squeeze may leave few alternative breeding habitats in developed regions. As a result, clutch relocation, a commonly used management tool to reduce egg loss, may become necessary for safeguarding populations. Although studies have examined the impact of relocation on clutch success, few have examined the impact of this practice on the sex or phenotypic characteristics of hatchlings produced. We used a randomized block design experiment to examine effects of relocation on green turtle (Chelonia mydas) clutches. We compared hatching success, thermal conditions, and size (length and mass) of hatchlings from in situ control clutches with those subjected to 2 relocation methods, while controlling for maternal and other environmental effects. Relocated clutches did not vary significantly from control clutches in incubation temperature or inferred sex ratios during the critical middle third of incubation when sex is thought to be determined. Hatchling size was also unaffected by relocation. Both relocation methods, however, resulted in a 20 reduction in hatching success in comparison to in situ clutches. Clutch relocation is, however, likely to affect the population primary sex ratio, when clutches are relocated from sites in proximity to the sea where tidal inundation is a threat. Here, cooler conditions are likely to produce more males than are the warmer female-producing temperatures higher up the beach. For clutches at risk, relocation is a viable process and does not appear to affect hatchling size or predicted sex ratios if relocation sites are selected in areas utilized by other females. We urge caution, however, when moving clutches from potentially male-producing sites, particularly given predicted impacts of climate change on already female-biased sex ratios. © 2009 the Wildlife Society.
Abstract.
Evans KL, Gaston KJ, Frantz AC, Simeoni M, Sharp SP, McGowan A, Dawson DA, Walasz K, Partecke J, Burke T, et al (2009). Independent colonization of multiple urban centres by a formerly forest specialist bird species.
Proc Biol Sci,
276(1666), 2403-2410.
Abstract:
Independent colonization of multiple urban centres by a formerly forest specialist bird species.
Urban areas are expanding rapidly, but a few native species have successfully colonized them. The processes underlying such colonization events are poorly understood. Using the blackbird Turdus merula, a former forest specialist that is now one of the most common urban birds in its range, we provide the first assessment of two contrasting urban colonization models. First, that urbanization occurred independently. Second, that following initial urbanization, urban-adapted individuals colonized other urban areas in a leapfrog manner. Previous analyses of spatial patterns in the timing of blackbird urbanization, and experimental introductions of urban and rural blackbirds to uncolonized cities, suggest that the leapfrog model is likely to apply. We found that, across the western Palaearctic, urban blackbird populations contain less genetic diversity than rural ones, urban populations are more strongly differentiated from each other than from rural populations and assignment tests support a rural source population for most urban individuals. In combination, these results provide much stronger support for the independent urbanization model than the leapfrog one. If the former model predominates, colonization of multiple urban centres will be particularly difficult when urbanization requires genetic adaptations, having implications for urban species diversity.
Abstract.
Author URL.
Evans KL, Gaston KJ, Sharp SP, McGowan A, Hatchwell BJ (2009). The effect of urbanisation on avian morphology and latitudinal gradients in body size.
Oikos,
118(2), 251-259.
Abstract:
The effect of urbanisation on avian morphology and latitudinal gradients in body size
Urban areas occupy a large and growing proportion of the earth. Such sites exhibit distinctive characteristics relative to adjacent rural habitats, and many species have colonised and now successfully exploit urban habitats. The change in selection pressures as a result of urbanisation has led to trait divergence in some urban populations relative to their rural counterparts, but studies have generally been local in scale and the generality of differentiation thus remains unknown. The European blackbird Turdus merula is one of the commonest urban bird species in the Western Palearctic, but populations vary substantially in the length of time they have been urbanised. Here we investigate patterns of morphological variation in European blackbirds occupying 11 paired urban and rural habitats across much of the urbanised range of this species and spanning 25° of latitude. First, we assessed the extent to which urban and rural blackbirds are differentiated morphologically and the consistency of any differentiation across the range. Paired urban and rural Blackbird populations frequently exhibited significant morphological differences, but the magnitude and direction of differentiation was site dependent. We then investigated whether the nature of latitudinal gradients in body-size differed between urban and rural populations, as predicted by differences in the climatic regimes of urban and rural areas. Blackbird body-size exhibited strong latitudinal gradients, but their form did not differ significantly between urban and rural habitats. The latitudinal gradient in body size may be a consequence of Seebohm's rule, that more migratory populations occurring at high latitudes have longer wings. We conclude that while there can be substantial morphological variation between adjacent urban and rural bird populations, such differentiation may not apply across a species' range. Locality specific differentiation of urban and rural blackbirds may arise if the selection pressures acting on blackbird morphology vary in an inconsistent manner between urban and rural habitats. Alternatively, phenotypic divergence could arise in a stochastic manner depending on the morphological traits of colonists, through founder effects. © 2009 the Authors.
Abstract.
2008
Broderick, A.C. Frett, G. Gore, S. (2008). Down But Not Out: Marine Turtles of the British Virgin Islands. Animal Conservation
Gan C-H, Tee S-M, Tang P-C, Yang JM-C, Freire F, McGowan A, Narriman J, Mohammed MS, Hsieh H-L, Chen C-P, et al (2008). Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro).
Mol Ecol Resour,
8(6), 1448-1450.
Abstract:
Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro).
The coconut crab (Birgus latro), an endangered marine-dispersed crustacean, is facing severe and probably accelerating population extinction worldwide, but biological information on its conservation remains deficient. In order to reveal the genetic structure of B. latro, 10 microsatellite loci were developed. A high degree of polymorphism was observed with a mean number of alleles per locus of 16.9. The mean expected heterozygosities were also high, ranging from 0.742 to 0.965. The observed heterozygosities ranged from 0.210 to 0.925. Departures from Hardy-Weinberg equilibrium were observed at five loci after the Bonferroni correction. These hypervariable markers will be utilized to study the genetic diversity and conservation of B. latro throughout its distribution range in the Pacific and Indian Oceans.
Abstract.
Author URL.
Mcgowan A, Broderick, A.C. Godley, B.J. (2008). Seabird populations of the Chagos Archipelago: an evaluation of IBA sites and a need for monitoring. Oryx
2007
McGowan A, Woodfield NK, Hilton G, Broderick AC, Godley BJ (2007). A rigorous assessment of the Avifauna of a small Caribbean Island: a case study in Anegada, British Virgin Islands.
Caribbean Journal of Science,
43(1), 99-116.
Abstract:
A rigorous assessment of the Avifauna of a small Caribbean Island: a case study in Anegada, British Virgin Islands
The avifauna of the British Virgin Islands (BVI) has received little attention from researchers. The lack of baseline information is therefore a major hindrance to the construction of management plans. Here we present detailed monitoring data on the species composition and numbers of each-species for the island of Anegada, BVI. We surveyed the birds of Anegada between November 2003 and March 2005 utilising a combination of coastal transects, wetland bird counts, point counts, and species-specific survey methods for nocturnal species. A total of 99 different species were recorded, with a large increase in the number of species and number of individuals centred around peak migration in September. Although there is a depauperate terrestrial bird community consisting of predominately generalist species, it holds important populations of regional avifauna. For example, it hosts five regionally important breeding seabird colonies and its wetlands provide an important stop-over and over-wintering site for many species of shorebirds and waterbirds. In addition, the Eastern salt ponds are also the only breeding site for the greater flamingo, Phoenicopterus ruber, within the territory. We discuss our findings within the current framework of regional conservation and provide recommendations for the implementation of a territory wide monitoring program as a first step towards meeting the UK's commitments under several multilateral environmental agreements. Copyright 2007 College of Arts and Science.
Abstract.
McGowan A, Wright LI, Hunt J (2007). Inbreeding and population dynamics: implications for conservation strategies. Animal Conservation, 10, 284-285.
Mcgowan A, Fowlie MK, Ross DJ, Hatchwell BJ (2007). Social organization of co-operatively breeding Long-tailed Tits Aegithalos caudatus: Flock composition and kinship. Ibis, 149(1), 170-174.
2006
Broderick, A.C. Gore, S. Hilton, G. (2006). Breeding seabirds in the British Virgin Islands.
Endangered Species Research,
3, 1-6.
Author URL.
McGowan A, Sharp SP, Simeoni M & Hatchwell BJ (2006). Competing for position in the communal roosts of long-tailed tits. Animal Behaviour, 76, 1035-1043.
2005
Sharp SP, McGowan A, Wood MJ & Hatchwell BJ (2005). Learned kin recognition cues in a social bird. Nature, 434, 1127-1130.
Dickinson JL & McGowan A (2005). Winter resource wealth drives delayed dispersal and family-group living in western bluebirds. Proceedings of the Royal Society B, 272, 2423-2428.
2004
Hatchwell BJ, Russell AF, MacColl ADC, Ross DJ, Fowlie MK, McGowan A (2004). Helpers increase long-term but not short-term productivity in cooperatively breeding long-tailed tits. Behavioral Ecology, 15, 1-10.
McGowan A, Sharp SP & Hatchwell BJ (2004). The structure and function of nests of long-tailed tits <em>Aegithalos caudatus</em>. Functional Ecology, 18, 578-583.
2003
McGowan a & Sharp S (2003). A family business.
McGowan A, Hatchwell BJ & Woodburn RJW (2003). The effect of helping behaviour on the survival of juvenile and adult long-tailed tits (<em>Aegithalo caudatus</em>). Journal of Animal Ecology, 72, 491-499.
2002
McGowan A, Cresswell W & Ruxton GD (2002). The effects of daily weather variation on foraging and responsiveness to disturbance in over-wintering Red Knot (<em>Calidris canutus</em>). Ardea, 90, 229-237.
2001
Broderick, A.C. Deeming, J. Godley, B.J. (2001). Dipteran infestation of loggerhead (Caretta caretta), and green (Chelonia mydas), sea turtle nests in northern Cyprus. Journal of natural History, 35, 573-581.
Hatchwell BJ, Ross DJ, Fowlie MK & McGowan A (2001). Kin discrimination in cooperatively breeding long-tailed tits. Proceedings of the Royal Society B, 268, 885-890.
McGowan A, Rowe, L.V. Broderick, A.C. Godley, B.J. (2001). Nest factors predisposing loggerhead sea turtle (Caretta caretta) clutches to infestation by dipteran larvae on northern Cyprus. Copeia, 2001(3), 808-812.
1997
Broderick AC, Godley BJ, Kelly a & McGowan A (1997). Glasgow University Turtle Conservation Expedition 1997: Expedition Report. Marine Turtle Research Group, Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow.
