Sula Dactylatra Research Articles

Resource partitioning influences levels of toxic trace elements in sympatric tropical seabirds

Morphologically similar species that occupy resource-limited environments tend to differ in their ecological traits in order to coexist, which may result in differential exposure to environmental threats. For instance, partitioning of feeding resources may influence contaminant exposure and bioaccumulation in marine predators through different diets or foraging habitats. Here, we sampled three tropical seabird species breeding in sympatry in the southwestern Atlantic Ocean for blood and feather trace element concentrations (As, Hg, Cd, Pb), and assessed their foraging ecology with bio-logging (GPS tracks and time-depth recorders), analysis of regurgitated prey, and carbon and nitrogen stable isotope mixing models. Red-billed tropicbirds (Phaethon aethereus), brown (Sula leucogaster) and masked (S. dactylatra) boobies differed in their preferred foraging locations, the range of foraging trips, diving parameters and diets. In addition, interspecific differences were detected in blood or feathers for all trace elements analyzed, suggesting influence of the differences observed in diet and space use. Red-billed tropicbirds had the largest foraging range over the continental shelf and over the slope, suggesting lower exposure to continental sources of metals. Brown and masked boobies had higher Hg concentrations than tropicbirds, higher δ15N values (a proxy for trophic level), and δ15N correlated with Hg levels, suggesting biomagnification of Hg along the food chain. Nonetheless, red-billed tropicbirds showed comparable levels of As and Cd in blood or feathers, and higher levels of Pb in both tissues in comparison to boobies, which may suggest overall exposure of seabirds in the region, through their diets and foraging areas. Resource partitioning is critical for allowing coexistence of different seabird species in shared breeding sites where they act as central-place foragers. Nonetheless, in scenarios of environmental pollution, these species-specific strategies lead to differential bioaccumulation, and thus distinct effects of pollution on populations are expected.

Cyclone Ilsa in April 2023 led to significant seabird mortality on Bedout Island

On 13 April 2023, Cyclone Ilsa crossed Bedout Island in the Timor Sea off Western Australia’s remote north coast. Extensive damage was done to the entire island, with all coastal vegetation stripped clear from the island’s surface. Here we use repeated aerial and ground-based transect surveys of Bedout’s important seabird populations during 17 April – 21 July 2023 and Monte Carlo modelling to estimate total mortality for three species. We estimate that 80–90% of the populations of three seabird species (Masked Booby Sula dactylatra bedouti, Brown Booby S. leucogaster, and Lesser Frigatebird Fregata ariel) were killed in the storm, with only 40 breeding Masked Booby (a putative endemic subspecies) recorded on the island 15 weeks later. The frequency and intensity of such storms is likely approaching a threshold beyond which Bedout’s seabirds cannot readily recover, with cyclones hitting the island, on average, every seven years in recent decades. We discuss the implications for Bedout Island, and for wildlife conservation more broadly in the face of increasing, climate-driven storms and impacts documented worldwide.

Role of environmental factors in the genetic structure of a highly mobile seabird

AbstractAimEnvironmental features can act as selection pressures and barriers to gene flow between populations. The genetic structuring of highly mobile but philopatric seabirds creates a paradox, and the role of oceanographic and geographic variables is still poorly understood. In this study, we investigate the influence of environmental and geographic variables in the genetic and phenotypic diversity of a pantropical seabird breeding in islands and archipelagos separated by different geographic distances, up to thousand kilometres, and which differ in environmental characteristics.LocationIslands and archipelagos in the southwestern (SW) Atlantic Ocean.Taxon Sula dactylatra, Lesson, 1831 (masked booby).MethodsThe population structure of the species was accessed through mitochondrial and nuclear DNA. To test Isolation by Environment (IBE) versus by Distance (IBD), sea surface temperature, primary productivity and salinity, as well as isotopic niche based on carbon and nitrogen, and distances between colonies and from the continent, were used. We also tested the correlation between the genetic structure and the morphometry of individuals in each colony.ResultsWe uncover the presence of low genetic structure between populations. Nevertheless, differences were identified between inshore and offshore colonies, with the influence of landscape characteristics of these two types of environment. The morphometric and isotopic niche variations are consistent with this segregation.Main ConclusionsEnvironmental variables of coastal and oceanic environments seem to influence the genetic structure of masked boobies, even though it is low in the SW Atlantic Ocean, highlighting the role of environmental heterogeneity in shaping biodiversity.

Pseudoscorpiones (Arachnida) of the Brazilian oceanic islands

Pseudoscorpiones are compose an ancient order of arachnids, occur in a wide variety of terrestrial habitats worldwide, with representatives of various genera occurring exclusively in insular habitats. The primary objective of this study was to determine the composition and distribution of Pseudoscorpiones within the Brazilian equatorial oceanic islands. To determine Pseudoscorpiones communities and distribution in coastal environmental habitats of the Brazilian equatorial oceanic islands (Fernando de Noronha archipelago, Rocas Atoll and St. Peter and St. Paul rocks), was defined three zones along the insular environmental gradient in the Brazilian equatorial oceanic islands. These zones include the Sand Beach (SB) closest to the intertidal zone, the Slope Forest (SF) with a sloping terrain and the Top Forest (TF) farthest from the beach. Collecting points were distributed in each zones (SB, SF, and TF) at distances greater than 1 km, with four samples collected at each point approximately 12.5 m apart from each other. The TF zone is observed only in Fernando de Noronha. In our study we found pseudoscorpions exclusively on the islands of the Fernando de Noronha archipelago. We collected 5 species from the Hesperolpiidae and Syarinidae families. The SF habitats exhibited greater species richness, while the Upper Forest habitats showed greater population abundance. Notably, we recorded pseudoscorpions (Ideoblothrus amazonicus) in bird nests (Sula dactylatra) on Rata Island, suggesting the use of nests as habitat, reproduction, and, possibly, occasional transport to and from other habitats. No pseudoscorpions were found in SB environments. Landscape changes and tourism can threaten this incredible newly discovered community, vital for monitoring environmental changes in this delicate ecosystem.

Variations in inter-specific and sex-related niche partitioning in pelagic boobies during their annual cycle.

Animals that co-occur in a region (sympatry) may share the same environment (syntopy), and niche differentiation is expected among closely related species competing for resources. The masked booby (Sula dactylatra) and smaller congeneric red-footed booby (Sula sula) share breeding grounds. In addition to the inter-specific size difference, females of both species are also larger than the respective males (reversed sexual size dimorphism). Although both boobies consume similar prey, sometimes in mixed-species flocks, each species and sex may specialize in terms of their diet or foraging habitats. We examined inter- and intra-specific differences in isotopic values (δ13C and δ15N) in these pelagically feeding booby species during the incubation period at Clarion Island, Mexico, to quantify the degrees of inter- and intra-specific niche partitioning throughout the annual cycle. During incubation, both species preyed mainly on flyingfish and squid, but masked boobies had heavier food loads than red-footed boobies. There was no overlap in isotopic niches between masked and red-footed boobies during breeding (determined from whole blood), but there was slight overlap during the non-breeding period (determined from body feathers). Female masked boobies had a higher trophic position than conspecific males during breeding; however, no such pattern was detected in red-footed boobies. These results provide evidence of inter- and intra-specific niche partitioning in these tropical seabird species, particularly during the breeding period and in the more-dimorphic species. Our results suggest that these closely related species use different strategies to cope with the same tropical marine environment.

Toxoplasma gondii antibodies in tropical seabirds from the Rocas Atoll Biological Reserve, Brazil.

Toxoplasma gondii is a coccidian that infects almost all warm-blooded animals, including birds. Rocas Atoll Biological Reserve, located in the northeast of Brazil, is the only atoll in the South Atlantic, and home to the largest population of seabirds in the western Atlantic. In this study the occurrence of T. gondii antibodies in seabirds from Rocas Atoll were determined. Birds were manually captured, blood samples were taken, and antibodies detected by the modified agglutination test (>5). In total, 267 birds of seven species belonging to three families (Sternidae, Fregatidae and Sulidae) and two orders (Charadriiformes and Suliformes) were sampled. Out of the 267 samples, 20 (7.3%) were seropositive: nine out of 48 brown noddies (Anous stolidus), one out of 26 black noddies (Anous minutus), three out of 20 magnificent frigatebirds (Fregata magnificens), five out of 95 sooty terns (Onychoprion fuscatus) and two out of 20 red-footed boobies (Sula sula). None of the 33 masked boobies (Sula dactylatra) and the 25 brown boobies (Sula leucogaster) were seropositive. The antibody titers were 5 (n=6), 10 (n=4), 20 (n=3), 40 (n=6) and 160 (n=1). Due to the uniqueness of this environment, monitoring the seabirds is suggested to maintaining this Conservation Unit.

The marine avifauna of Matthew and Hunter Islands, two remote volcanoes of the New Hebrides chain

The marine avifauna of Matthew and Hunter Islands, two remote volcanoes of the New Hebrides chain Breeding birds recorded on Matthew and Hunter Islands in the tropical southwestern Pacific between 1973 and 2018 are summarised from a compilation of reports, for which various methods were used for counting seabirds. These methods included line transects, or direct observations using telescope or binoculars, or exhaustive counts, depending on the species observed and its nesting habitat. Population size estimates and reproductive periods are given. The total number of seabird species recorded breeding on the two islands was n = 14. This total includes seabird species breeding on both islands (n = 7): black-winged petrel Pterodroma nigripennis, wedge-tailed shearwater Ardenna pacifica, red-tailed tropicbird Phaethon rubricauda, masked booby Sula dactylatra, brown booby S. leucogaster, brown noddy Anous stolidus, and grey noddy A. albivitta. Hunter island also harbours a small colony of Herald petrel Pterodroma heraldica, and colonies of lesser and great frigatebirds (Fregata ariel and F. minor), red-footed booby S. sula and, black noddy A. minutus and white tern Gygis alba. Matthew Island harbours a large colony of sooty tern Onychoprion fuscatus; an undetermined storm petrel may also breed there. Differences between the two islands regarding community composition of seabirds are explained by the absence of trees on Matthew Island and the presence of the Polynesian rat Rattus exulans on Hunter Island. Brown noddies bred exclusively during the austral summer, as did black-winged petrels and wedge-tailed shearwaters, while the Herald petrel and the two frigatebirds seemed to preferentially breed in the winter. The red-tailed tropicbird, the three boobies, the grey noddy and the sooty tern appeared to reproduce year-round. Disturbance caused by human activities was irregular but devastating to seabird colonies. The diversity and abundance of seabird species breeding on these islands makes them regionally important sites for conservation. Key words: Seabird, Population, Reproduction, Threats, Polynesian rat; Helicopters

Cover Image

Ecological ApplicationsVolume 33, Issue 2 e2658 COVER IMAGEFree Access Cover Image First published: 01 March 2023 https://doi.org/10.1002/eap.2658AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract COVER PHOTO: A pair of Masked Boobies (Sula dactylatra) at sunset in the Abrolhos Archipelago, northeast Brazil. In their study published in this issue, Linhares and Bugoni (Article e2733, doi:10.1002/eap.2733) highlight how seabirds transport marine-derived nutrients to colonies, which subsidize multiple organisms in the terrestrial food web and corals around some of the islands, despite the presence of invasive rats and their associated impacts. Photo credit: Bruno A. Linhares. Volume33, Issue2March 2023e2658 RelatedInformation

Persistent organic pollutant patterns in seabirds from marine protected areas in the tropical Atlantic Ocean

Persistent organic pollutants were investigated in the blood of living seabirds (Pterodroma arminjoniana, Onychoprion fuscatus, Sula dactylatra, Anous minutus, Anous stolidus and Sula leucogaster) from two Brazilian Conservation Units - Trindade Island and São Pedro and São Paulo Archipelago. ∑PCBs (0.55 to 55.09 ng/g wet weight (ww), ∑DDTs (0.01 to 17.36 ng/g ww) and Mirex (0.01 to 5.53 ng/g ww) were predominant in all samples. Trindade petrel Pterodroma arminjoniana presented higher values than other seabirds, which is potentially related to diet and migratory behavior. Fluctuations in the trophic ecology data, through carbon and nitrogen stable isotope ratios, warn of temporal variation in diet and foraging and highlight the importance of using a nondestructive matrix to allow long-term monitoring of POP contamination in seabirds from Brazilian Conservation Units. In addition, the data will fill the gaps in the POP baselines for seabirds from the tropical Atlantic Ocean.

Dissipation of seabird‐derived nutrients in a terrestrial insular trophic web

AbstractHighly mobile organisms can transport nutrients and energy among distinct ecosystems, such as between oceanic foraging areas and terrestrial breeding sites. Seabirds are great nutrient carriers and potentially play a key role in the maintenance of trophic webs on islands. In this study, we assessed three dimensions of marine nutrient dissipation—horizontal, temporal and vertical—on the tropical Meio Island of Fernando de Noronha Archipelago, Brazil. For this, C3 and C4 plants, ants and spiders found in a 100 m long transect between colonies of masked (Sula dactylatra) and red‐footed boobies (Sula sula) were sampled during the rainy (the masked booby breeding period) and dry seasons (the red‐footed booby breeding period). The marine contribution to the terrestrial trophic web was analysed using Bayesian mixing models from a carbon and nitrogen stable isotope data set. The main findings indicate that marine nutrients in the terrestrial trophic web dissipated horizontally as the distance from the colony increased, which was more marked during the rainy season. On the vertical axis, the relative contribution of marine nutrients in terrestrial consumers was strongly related to food habits but not necessarily to the trophic level, dissipating rather than increasing, due to variable omnivory and the use of terrestrial food sources. The breeding strategy of the masked booby (i.e. incubating eggs on the ground), in addition to a larger body size and larger colony, could produce a more concentrated pulse of nutrients in comparison to seabirds nesting sparsely on trees, contributing more efficiently to the enrichment of marine nutrients on land. The importance of seabirds for the maintenance of interconnected ecosystems has been demonstrated, and the role of marine‐derived nutrients in the enrichment of nutrient‐poor tropical islands.

Did the animal move? A cross-wavelet approach to geolocation data reveals year-round whereabouts of a resident seabird

Considerable progress in our understanding of long-distance migration has been achieved thanks to the use of small geolocator devices (GLS). The tracking of resident or short-distance migrant animals remains however challenging because geolocation errors are substantial and difficult to estimate. This study aims to examine the sex-specific marine space uses of a resident tropical seabird, the masked booby (Sula dactylatra), during its full annual life cycle at the Fernando de Noronha archipelago (Brazil). Masked boobies (n = 31) tagged with GLS recording light intensity, seawater immersion, and water temperature showed a resident behaviour over their entire annual cycle. A wavelet analysis of GLS data revealed oscillatory patterns of inferred longitude correlated with changes in immersion frequency. This synchronicity demonstrated that birds traveled away and back from the colony on consecutive trips of short length (\(\sim\) 2–4 days) and short range (\(\sim\) 100–300 km) eastward of the colony. Duration and range of trips depended on the sex of the individual and on the time of the year. Trip duration increased gradually from the end of the breeding period to the post-breeding period, probably due to the release of the central-place breeding constraints. During the pre-breeding period, females had farther ranges eastward and spent more time in water than males. Despite inherent limits of light-based geolocation, this study demonstrates the relevance of synchronicity analysis of GLS data for investigating year-round movements of resident or short-distance migrants.

Linking foraging and breeding strategies in tropical seabirds

The archetypal foraging behaviour of tropical seabirds is generally accepted to differ from that of their temperate and polar breeding counterparts, with the former exhibiting less predictable foraging behaviour associated with the less predictable prey of the tropical marine environment. Similarly, temperate and polar species have predictable, annual breeding seasons, enabling them to profit during periods of the year when prey availability is highest, while tropical seabird species exhibit considerable variability in their breeding strategies. Until now, the reasons for such variation in breeding strategies between tropical seabirds are yet to be investigated. We hypothesise that while some tropical species breed asynchronously in response to unpredictable fluctuations in prey availability, others adopt a seasonal breeding strategy for the same reasons that temperate and polar species do. Consequently, the predictability of seabird foraging behaviour in the tropics may be related to breeding strategy, with populations that breed seasonally exhibiting more predictable foraging behaviour than those that breed aseasonally. To test these predictions, we used GPS tracking to examine the foraging behaviour of two closely related tropical seabird species that colonise the same island yet exhibit markedly different breeding strategies: the asynchronously breeding brown booby Sula leucogaster and the seasonal breeding masked booby Sula dactylatra. We obtained tracks for 251 birds over five years. We found that brown boobies forage less predictably than masked boobies, indicated by larger core foraging areas, lower levels of foraging area overlap between individuals and exhibit more variability between breeding periods. Our results challenge the view that the foraging behaviour of tropical seabirds is always less predictable than that of seabirds breeding in temperate and polar regions and highlight the considerable variability in the breeding and foraging strategies adopted by tropical seabirds which demand further exploration.

Trends in seabird breeding populations across the Great Barrier Reef.

The Great Barrier Reef is an iconic ecosystem, known globally for its rich marine biodiversity that includes many thousands of tropical breeding seabirds. Despite indications of localized declines in some seabird species from as early as the mid‐1990s, trends in seabird populations across the reef have never been quantified. With a long history of human impact and ongoing environmental change, seabirds are likely sentinels in this important ecosystem. Using 4 decades of monitoring data, we estimated site‐specific trends for 9 seabird species from 32 islands and cays across the reef. Trends varied markedly among species and sites, but probable declines occurred at 45% of the 86 species‐by‐site combinations analyzed compared with increases at 14%. For 5 species, we combined site‐specific trends into a multisite trend in scaled abundance, which revealed probable declines of Common Noddy (Anous stolidus), Sooty Tern (Onychoprion fuscatus), and Masked Booby (Sula dactylatra), but no long‐term changes in the 2 most widely distributed species, Greater Crested Tern (Thalasseus bergii) and Brown Booby (Sula leucogaster). For Brown Booby, long‐term stability largely resulted from increases at a single large colony on East Fairfax Island that offset declines at most other sites. Although growth of the Brown Booby population on East Fairfax points to the likely success of habitat restoration on the island, it also highlights a general vulnerability wherein large numbers of some species are concentrated at a small number of key sites. Identifying drivers of variation in population change across species and sites while ensuring long‐term protection of key sites will be essential to securing the future of seabirds on the reef.

Breeding stage, not sex, affects foraging characteristics in masked boobies at Rapa Nui

Sexual segregation in foraging occurs in some species and populations of boobies (Sulidae), but it is not a general pattern. Sexual segregation in foraging may occur to avoid competition for food, and this competition may intensify during specific stages of breeding. We examined sexual segregation in foraging in relation to breeding stage in masked boobies Sula dactylatra at Rapa Nui by tracking simultaneously incubating and chick-rearing birds using GPS recorders (n = 18) and collected a total of 11 regurgitate samples. Stable isotope analyses (δ13C and δ15N) of whole blood samples were carried out in 20 birds. There were no differences in foraging trip parameters or diet between females and males. Both sexes traveled farther and for longer while incubating than while rearing chicks. Isotopic niches (δ13C and δ15N) overlapped to some degree among all groups at all times, but the lowest overlap between sexes occurred during incubation. While preying on ephemerally distributed flying fish, vertical or horizontal competition avoidance may be almost impossible, and thus females and males share their foraging grounds. Since birds were tracked simultaneously, shorter foraging trips of chick-rearing birds must be an effect of the constraints of provisioning the chick. Differences observed in δ15N and δ13C values between sexes may be caused by subtle differences in their foraging behaviors, or by differences in physiology linked to breeding. Our findings suggest that local oceanography and its inherent food distribution are determinants for sexual segregation in foraging patterns in masked boobies and possibly also other booby species.Significance statementIn some animals, females and males forage on different areas or prey on different species to avoid competition for food resources. In boobies (Sula sp.), some studies show evidence of sexual segregation in foraging and others do not. Here, we tested if sexual segregation in foraging occurred in masked boobies on the Pacific island of Rapa Nui by studying simultaneously incubating and chick-rearing birds. We found no evidence of sexual segregation on foraging behavior or diet. We discuss that the difference between this and other studies in boobies may be an effect of the local prey availability. When the prey community is more diverse and heterogeneously distributed, each sex may access different resources and thus sexual foraging segregation will occur. In contrast, in areas like Rapa Nui where prey resources are distributed ephemerally, sexual segregation in foraging will not be useful and is thus less likely to occur.

Foraging ecology of a marine top predator in the Eastern Tropical Pacific over 3\xa0years with different ENSO phases

The El Niño Southern Oscillation (ENSO) is a recurrent climatic pattern with important ecological consequences for seabirds due to its impacts on the abundance and distribution of food resources. We investigated the effects of ENSO phases on the foraging ecology of a marine top predator at Clarion Island in the Eastern Tropical Pacific using GPS and time-depth recorder data and regurgitates from incubating masked boobies (Sula dactylatra) during 3 consecutive years. Foraging locations were recorded in 2016 (El Niño, one female, three males), 2017 (neutral; six females, nine males), and 2018 (La Niña; eight females, ten males). Local sea surface temperature (SST) and chlorophyll-a concentration (CHL) within the birds’ foraging range were compared among the 3 years. Regurgitates were collected opportunistically from 25 and 31 incubating adults in 2017 and 2018, respectively. Average local CHL and SST were similar among years (mean SST 25 °C; mean CHL 0.10 and of 0.09 mg m−3 in January and March, respectively). Masked boobies travelled a maximum of 66 ± 34 km from the colony. The maximum trip duration was 7.7 ± 3.4 h and total distance travelled during a foraging trip was 164 ± 73 km, with no sex- or year-related differences. Masked boobies mainly caught flying fish, but their diet also included one squid and six other fish families. In contrast to previously reported changes in foraging ecology of seabirds, masked boobies at Clarion Island seemed to be unaffected during El Niño, because the local oceanography was relatively unperturbed by ENSO oscillations.

Foraging ecology of masked boobies (Sula dactylatra) in the world\u2019s largest \u201coceanic desert\u201d

The South Pacific Gyre has the most hyper-oligotrophic waters in the world and is considered the largest “oceanic desert.” Rapa Nui (Easter Island), located within the South Pacific Gyre, is a breeding ground for masked boobies (Sula dactylatra), which are seabirds with a foraging range that effectively confines them within the gyre. The foraging ecology of this species in the gyre was examined by attaching GPS and time-depth devices to chick-rearing adult birds (9 and 14 birds in 2016 and 2017, respectively) and by collecting regurgitates (18 and 15 samples in 2016 and 2017, respectively). In addition, the birds’ foraging ecology between years was compared. Masked boobies traveled in various directions, dived at unspecific locations, and explored areas < 110 km from the colony. Local environmental conditions were not significantly different between years, and differences in foraging parameters (maximum foraging range, trip duration, and dive depth) were greater among individuals than between years. The foraging characteristics of masked boobies suggest that resources were ephemerally distributed around the colony, with similar abundances across years. Under these conditions, traveling to unspecific locations may increase the area covered and the probability of prey encounter. The spatial and temporal consistencies in environmental conditions explain the uniformity of foraging parameters between years. The ability of masked boobies to exploit ephemerally distributed resources in seascapes like Rapa Nui may help explain its pantropical distribution.

High spatial fidelity among foraging trips of Masked Boobies from Pedro Cays, Jamaica.

In marine environments, tropical and subtropical habitats are considered to be inherently less productive than more temperate systems. As such, foraging site fidelity among vertebrate predators occupying low-latitude marine systems is generally low as a response to an increased unpredictability of resources. We investigated the foraging movements of Masked Boobies breeding on Middle Cay, Jamaica using GPS loggers to examine if the presence of a nearby bathymetric feature influenced foraging site fidelity in a tropical system, the Caribbean Sea. According to the movements of tracked individuals, this population of boobies shows a high degree of spatial fidelity in foraging site selection, concentrated on the northern edge of Pedro Bank. We suggest this feature as an important location for marine conservation in the region and demonstrate its utility to foraging boobies via habitat modeling using a maximum entropy approach of relevant habitat variables. Finally, we place this study into the global context of Masked Booby foraging by examining the published literature of relevant tracking studies for population-level similarity in foraging metrics. According to hierarchical clustering of foraging effort, Masked Boobies demonstrate a density-dependent response to foraging effort regardless of colony origin or oceanic basin consistent with the principles of Ashmole's Halo.

Trace element concentrations in feathers from three seabird species breeding in the Timor Sea

Mobile marine predators, such as seabirds, are frequently used as broad samplers of contaminants that are widespread in the marine environment. The Timor Sea off remote Western Australia is a poorly studied, yet rapidly expanding area of offshore development. To provide much needed data on contamination in this region, we quantified trace element concentrations in breast feathers of three seabird species breeding on Bedout Island. While adult Masked Boobies Sula dactylatra exhibited some of the highest concentrations, values for all species were below toxicology thresholds for seabirds and were comparable to those reported in other closely related species. The low concentrations detected in the birds provide a valuable baseline and suggest that the local marine environment around Bedout is in relatively good condition. However, careful monitoring is warranted in light increasing anthropogenic activity in this region.

Fast genomic analysis of aquatic bird populations from short single-end reads considering sex-related pitfalls

Population genomics is transforming the analyses of biodiversity, particularly the studies in conservation genetics. However, genomic approaches based on short sequencing reads are often subjected to complex molecular protocols and bioinformatics procedures, which are prone to many artifactual biases. In preliminary analyses using common pipelines for handling, filtering and processing genotyping-by-sequencing (GBS) data from three aquatic bird species, we detected a bias likely associated to the sex of individuals of the genus Sula, which could be due to artifacts with sex chromosome derived reads. Thus, we have developed GBirdS, a new pipeline for avian population genetics from GBS data, implementing a new approach to identify molecular markers likely to be linked to the avian W chromosome. The pipeline was applied to a total of 113 samples from three avian species (Sula leucogaster, Sula dactylatra and Mergus octosetaceus), including 54 samples for which the molecular sexing was available. For 53 out of these 54 samples, the sex determination achieved using GBirdS agreed with molecular sexing. We have then removed from subsequent population analyses the sequences observed only in individuals determined as heterogametic (likely to be females) by our pipeline. Removing these sequences resulted in greater average fixation indexes between subpopulations of these three species. Therefore, we conclude that the sequences removed by our pipeline had an artificial effect on interindividual differences and population structure.

Ecomorphology and foraging behaviour of Pacific boobies

Wing size and shape, expressed as wing loading and aspect ratio respectively, together with bill morphology are parameters that can reveal differences related to the foraging ecology of seabirds. Six species of booby (Sulidae) that inhabit the Pacific are the focus of this study: four mainly pelagic species, Masked Booby Sula dactylatra, Nazca Booby Sula granti, Red‐footed Booby Sula sula and Brown Booby Sula leucogaster, and two coastal species, Blue‐footed Booby Sula nebouxii and Peruvian Booby Sula variegata. Pelagic boobies showed segregation among species in body mass and relative bill size, and they differed in wing morphology (wing loading and aspect ratio) from the coastal boobies. The coastal Peruvian and Blue‐footed Boobies are largely allopatric but overlap in northern Peru. In their area of sympatry, they showed evidence of character displacement in body size and in wing and bill morphology, which suggests that competition plays an important role in sympatry. This study improves our understanding of ecological interactions among Pacific boobies and of how selective pressures have shaped their ecomorphology and foraging behaviours.