Sexual and individual signatures are encoded in the temporal rate of Cape gannet display calls

Vocalisations play a vital role in animal communication, as they are involved in many biological functions. Seabirds often breed in large and dense colonies, making successful recognition between mates or between parents-and offspring crucial for reproductive success. Most seabird species, including Cape gannets (Morus capensis), are monomorphic and likely rely on acoustic signals for mate selection and mate recognition. This study aimed to better understand the use of vocalisations for sex and individual recognition in Cape gannets by describing the acoustic structure of their display calls at the nest. Vocalisations of nesting Cape gannets were recorded and acoustic measurements were extracted in both temporal and frequency domains. Values of the fundamental frequency and the average of Inter-Onset-Interval appeared to be the most important acoustic variables for sex determination. Both temporal and frequency parameters showed a potential for individual identity coding, with the average units Inter-Onset-Interval being the most important variable for individual identification for both sexes. This study provides the first evidence of sex-specific and individual vocal signatures in adult breeding Cape gannets. From an applied perspective, identified sex specific differences could potentially be used as a non-invasive method for field-based sex-determination in research and monitoring projects on Cape gannets.

Conservation Genomics Reveals Low Connectivity Among Populations of Threatened Roseate Terns in the Atlantic Basin

While the effects of barriers to dispersal such as population declines, habitat fragmentation, and geographic distance have been well-documented in terrestrial wildlife, factors impeding the dispersal of highly vagile taxa such as seabirds are less well understood. The roseate tern (Sterna dougallii) is a globally distributed seabird species, but populations tend to be both fragmented and small, and the species is declining across most of its range. Within the Atlantic Basin, past work has shown differentiation among roseate terns breeding on different continents, but these results were generated with a limited number of microsatellite markers. Relationships between breeding populations in the Northwestern Atlantic and the Caribbean have never been analyzed. We evaluated population structuring of roseate tern populations in North America and the Azores using both microsatellite markers and single-nucleotide polymorphisms generated through targeted sequencing of Ultra-conserved Elements. For both marker types, we found significant genetic differentiation among all 3 populations and evidence for moderate contemporary unidirectional gene flow from the Caribbean to the Azores, but not among other populations. Within the Caribbean metapopulation, we found high rates of unidirectional migration from the Virgin Islands to Florida, potentially indicative of movement from source population to sink or an artifact of dispersal among other unsampled populations in the Caribbean region. These observations have significance for species persistence in the Atlantic, as our results suggest that loss of genetic diversity within populations is unlikely to be buffered by inflow of new alleles from other breeding populations.

Importation of plastic fragments into a seabird colony: accident or design, threat or benign?

Summary Plastic pollution affects marine ecosystems worldwide and poses risks for seabirds. Most recorded impacts on organisms are negative but, in some cases, the constructive use of plastic fragments or objects by birds has also been recorded. Small blue and green plastic fragments are found scattered among nests in a large (c.500,000 pairs) Sooty Tern Onychoprion fuscatus nesting colony on Bird Island, Seychelles. We investigated whether the fragments were being imported by the birds, and if so whether import was accidental or intentional. We found that Sooty Terns were the only seabird species to have plastic fragments in their nesting area and import of fragments varied seasonally and spatially. Throughout the colony, plastic fragments were imported during egg-laying, incubation, and chick-rearing, but import declined as chicks began to fledge. A part of the colony where all eggs were harvested for human consumption received more fragments than among undisturbed nests. We failed to find evidence of ingestion and excretion of fragments and suggest other avenues for investigation.

Why do we monitor? Using seabird eggs to track trends in Arctic environmental contamination

Contaminant levels and trends have been monitored in eggs of seabirds from the Canadian Arctic since 1975. Nearly 50 years of monitoring have provided key information regarding the temporal and spatial variation of various contaminant classes in different seabird species. However, previous work has primarily assessed individual or related contaminant classes in isolation. There is therefore a need to collectively consider all of the contaminants monitored in seabird eggs to determine where monitoring has been successful, to find areas for improvement, and to identify opportunities for future research. In this review, we evaluated monitoring data for the major legacy and emerging contaminants of concern in five seabird species from three High Arctic and three Low Arctic colonies in Canada. We review the history of Canada’s Arctic seabird egg monitoring program and discuss how monitoring efforts have changed over time; we summarize temporal, spatial, and interspecies variations in Arctic seabird egg contamination and identify important knowledge gaps; and we discuss future directions for ecotoxicology research using seabird eggs in Arctic Canada. Ultimately, this paper provides a high-level overview of the egg contaminant monitoring program and underscores the importance of long-term and continued seabird contaminant monitoring in Arctic Canada.

A call for observations of birds with sublingual oral fistulas in central and eastern Europe, and beyond

Birds with major physical abnormalities do not live for extended periods and, therefore, are rarely observed in the wild. This is particularly the case for birds with defects in their feeding apparatus that succumb to mortality rapidly through precipitous declines in their foraging efficiency and body condition. Sublingual oral fistulas are such an abnormality and involve the development of an opening (or fistula) in the floor of the oral cavity through which the tongue extends, resulting in its permanent exclusion from the mouth. The tongue dehydrates and dies. First described in the 2000s in Stitchbirds (Notiomystis cincta) in New Zealand, it has rarely been reported in other species. However, following our recent discovery of two seabird species on Ascension Island in the South Atlantic displaying oral fistulas, in 2016 I launched a citizen science research project requesting reports of birds with the condition in the world’s avifauna. To date, I have received 188 reports of birds of 82 different species with many contributed from western Europe. However, with only one report from central and eastern Europe, I am now requesting the assistance of birders in the region and in other parts of the world to contribute to this ongoing research project.

Effects of competitive pressure and habitat heterogeneity on niche partitioning between Arctic and boreal congeners

The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey but also that of competitors (e.g. southerly species expanding their range into the Arctic). Species can respond to interspecific competition by segregating along different niche axes. Here, we studied spatial, temporal and habitat segregation between two closely related seabird species: common guillemot Uria aalge (a temperate species) and Brünnich’s guillemot Uria lomvia (a true Arctic species), at two sympatric sites in Iceland that differ in their total population sizes and the availability of marine habitats. We deployed GPS and temperature-depth recorders to describe foraging locations and behaviour of incubating and chick-rearing adults. We found similar evidence of spatial segregation at the two sites (i.e. independent of population sizes), although segregation in environmental space was only evident at the site with a strong habitat gradient. Unexpectedly, temporal (and, to a limited extent, vertical) segregation appeared only at the least populated site. Overall, our results show complex relationships between the levels of inferred competition and that of segregation.

Seabird Migration Strategies: Flight Budgets, Diel Activity Patterns, and Lunar Influence

Every year, billions of birds undertake extensive migrations between breeding and non-breeding areas, facing challenges that require behavioural adjustments, particularly to flight timing and duration. Such adjustments in daily activity patterns and the influence of extrinsic factors (e.g., environmental conditions, moonlight) have received much more research attention in terrestrial than marine migrants. Taking advantage of the widespread deployment in recent decades of combined light-level geolocator-immersion loggers, we investigated diel organisation and influence of the moon on flight activities during the non-breeding season of 21 migrant seabird species from a wide taxonomic range (6 families, 3 orders). Migrant seabirds regularly stopped (to either feed or rest) during migration, unlike some terrestrial and wetland birds which fly non-stop. We found an overall increase for most seabird species in time in flight and, for several species, also in flight bout duration, during migration compared to when resident at the non-breeding grounds. Additionally, several nocturnal species spent more of the day in flight during migration than at non-breeding areas, and vice versa for diurnal species. Nocturnal time in flight tended to increase during full moon, both during migration and at the non-breeding grounds, depending on species. Our study provides an extensive overview of activity patterns of migrant seabirds, paving the way for further research on the underlying mechanisms and drivers.

Climate driven spatiotemporal variations in seabird bycatch hotspots and implications for seabird bycatch mitigation

Bycatch in fisheries is a major threat to many seabird species. Understanding and predicting spatiotemporal changes in seabird bycatch from fisheries might be the key to mitigation. Inter-annual spatiotemporal patterns are evident in seabird bycatch of the U.S. Atlantic pelagic longline fishery monitored by the National Marine Fisheries Service Pelagic Observer Program (POP) since 1992. A newly developed fast computing Bayesian approximation method provided the opportunity to use POP data to understand spatiotemporal patterns, including temporal changes in location of seabird bycatch hotspots. A Bayesian model was developed to capture the inherent spatiotemporal structure in seabird bycatch and reduce the bias caused by physical barriers such as coastlines. The model was applied to the logbook data to estimate seabird bycatch for each longline set, and the mid-Atlantic bight and northeast coast were the fishing areas with the highest fleet bycatch estimate. Inter-annual changes in predicted bycatch hotspots were correlated with Gulf Stream meanders, suggesting that predictable patterns in Gulf Stream meanders could enable advanced planning of fishing fleet schedules and areas of operation. The greater the Gulf Stream North Wall index, the more northerly the seabird bycatch hotspot two years later. A simulation study suggested that switching fishing fleets from the hindcasted actual bycatch hotspot to neighboring areas and/or different periods could be an efficient strategy to decrease seabird bycatch while largely maintaining fishers’ benefit.

Tracking the movements of North Atlantic seabirds: steps towards a better understanding of population dynamics and marine ecosystem conservation

Many seabird species undergo extensive seasonal migrations, often across large marine ecosystems or between marine areas under different national jurisdictions. With the advances of electronic tracking, especially of the application of Global Location Sensors (GLS or geolocators), it is now possible to study the seasonal movements of seabirds and link breeding populations to non-breeding habitats. To take full advantage of this development for better management and conservation, and to broaden the scope of scientific questions that can be assessed, there is a need for large-scale and multi-species programmes. The SEATRACK project with partners from 10 countries is ongoing and aims to identify the year-round distribution and movements of seabirds breeding in colonies across the northern part of the North Atlantic. By 2020, 14534 loggers were deployed on 11 species, and data from 5440 retrieved loggers have been analyzed and compiled. This Theme Section assembles original research articles based on data collected as part of the SEATRACK project from 2014 to 2019. A series of 11 papers advances the knowledge within 4 research themes: (1) variation in migration strategies among individuals, populations and species; (2) linking migration strategies and winter distribution to seabird demography and population dynamics; (3) linking migration and winter distribution to contaminants in seabirds and (4) the use of GLS data in marine spatial planning. We review existing literature within SEATRACK’s 4 themes with a focus on the temperate and arctic zones of the North Atlantic to provide a framework within which to discuss the 11 contributions and provide recommendations for future research.

Population ecology of seabirds in Mexican Islands at the California Current System

The Baja California Pacific Islands (BCPI) is a seabird hotspot in the southern California Current System supporting 129 seabird breeding populations of 23 species and over one million birds annually. These islands had a history of environmental degradation because of invasive alien species, human disturbance, and contaminants that caused the extirpation of 27 seabird populations. Most of the invasive mammals have been eradicated and breeding colonies have been restored with social attraction techniques. We have systematic information for most of the breeding populations since 2008. To assess population trends, we analyzed data and present results for 19 seabird species on ten island groups. The maximum number of breeding pairs for each nesting season was used to estimate the population growth rate (λ) for each species at every island colony. We performed a nonparametric bootstrapping to assess whether seabird breeding populations are increasing or decreasing. San Benito, Natividad, and San Jerónimo are the top three islands in terms of abundance of breeding pairs. The most widespread species is Cassin’s Auklet with 14 colonies. Twenty-three populations of 13 species are significantly increasing while eight populations of six species are decreasing. We did not find statistical significance for 30 populations, however, 20 have λ>1 which suggest they are growing. Seven of the 18 species for which we estimated a regional population trend are significantly increasing, including three surface-nesting species: Brown Pelican, Elegant Tern and Laysan Albatross, and four burrow-nesting species: Ainley’s and Ashy Storm-Petrels, and Craveri’s and Guadalupe Murrelet. Our results suggest that the BCPI support healthy and growing populations of seabirds that have shown to be resilient to extreme environmental conditions such as the “Blob”, and that such resilience has been strengthen from conservation and restoration actions such as the eradication of invasive mammals and social attraction techniques.