No abstract

Climate change can drive population declines for many species, often through changes to their food supply. These changes can involve a mis-timing between periods of high food demand and peak food availability, typically from advances in breeding phenology, and/or an overall reduction in food availability. Aerial insectivores, birds that feed on insects caught in flight, are experiencing steep population declines possibly because of shifts in the timing and/or abundance of aerial insects. We determined whether changes in breeding performance over time could account for declines in Bank Riparia riparia, Barn Hirundo rustica, Cliff Petrochelidon pyrrhonota, and Tree Tachycineta bicolor Swallows, and if so, whether changes were related to shifts in breeding phenology and/or climate change. We compared breeding performance and phenology in Maritime Canada before (1962)(1963)(1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972) and after (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) the onset of steep population declines during the mid-1980s, to determine whether breeding performance was reduced or phenology was advanced. Then, we modeled relationships between temperature, precipitation, breeding phenology, and performance for Barn and Tree Swallows, the only species with sufficient data, from 1960 to 2016, to determine whether phenology and performance were related to climatic conditions. Between the two time periods, we found significantly lower performance in Bank Swallows, higher performance in Barn and Tree Swallows, and unchanged performance in Cliff Swallows. We also found clutch initiation dates advanced by 8-10 d for all species except Bank Swallows. On the breeding grounds, warmer winter temperatures for Tree Swallows and less winter precipitation for Barn and Tree Swallows in a given year were associated with earlier breeding, and for Tree Swallows, changes in nestling survival. Otherwise, Barn and Tree Swallow breeding performance was unaffected by winter temperature and precipitation. Our results suggest that in this region poorer breeding performance could contribute to population declines for Bank Swallows but not for the other three species.

1. Light-level geolocators are popular bio-logging tools, with advantageous sizes, longevity and affordability. Biologists tracking seabirds often presume geolocator spatial accuracies between 186 and 202 km from previously innovative, yet taxonomically, spatially and computationally limited, studies. Using recently developed methods, we investigated whether assumed uncertainty norms held across a larger-scale, multispecies study.2. We field-tested geolocator spatial accuracy by synchronously deploying these with GPS loggers on scores of seabirds across five species and 11 Mediterranean Sea, east Atlantic and south Pacific breeding colonies. We first interpolated geolocations using the geolocation package FLightR without prior knowledge of GPS tracked routes. We likewise applied another package, probGLS, additionally testing whether sea-surface temperatures could improve route accuracy.3. Geolocator spatial accuracy was lower than the ~200 km often assumed. prob-GLS produced the best accuracy (mean ± SD = 304 ± 413 km, n = 185 deployments) with 84.5% of GPS-derived latitudes and 88.8% of longitudes falling within resulting uncertainty estimates. FLightR produced lower spatial accuracy (408 ± 473 km, n = 171 deployments) with 38.6% of GPS-derived latitudes and 23.7% of longitudes within package-specific uncertainty estimates. Expected inter-twilight period (from GPS position and date) was the strongest predictor of accuracy, with increasingly equatorial solar profiles (i.e. closer temporally to equinoxes and/or spatially to the Equator) inducing more error. Individuals, species and geolocator model also significantly affected accuracy, while the impact of distance travelled between successive twilights depended on the geolocation package.4. Geolocation accuracy is not uniform among seabird species and can be considerably lower than assumed. Individual idiosyncrasies and spatiotemporal dynamics

Summary Pelagic seabird populations have declined strongly worldwide. In the North Atlantic there was a huge reduction in seabird populations following the European colonization of the Azores, Madeira and Canary archipelagos but information on seabird status and distribution for the subtropical region of Cabo Verde is scarce, unavailable or dispersed in grey literature. We compiled and compared the historical and current distribution of all seabird species breeding in the Cabo Verde archipelago, updated their relative abundance, investigated their inland habitat preferences, and reviewed their threats. Currently, the breeding seabird community in Cabo Verde is composed of Bulwer’s Petrel Bulweria bulwerii, White-faced Storm-petrel Pelagodroma marina aedesorum, Cape Verde Shearwater Calonectris edwardsii, Cape Verde Storm-petrel Hydrobates jabejabe, Cape Verde Petrel Pterodroma feae, Boyd's Shearwater Puffinus lherminieri boydi, Brown Booby Sula leucogaster, and Red-billed Tropicbird Phaethon aethereus. One breeding species is currently extinct, the Magnificent Frigatebird Fregata magnificens. The relative abundance of Cape Verde Shearwater, Boyd’s Shearwater, Cape Verde Petrel, and Cape Verde Storm-petrel was determined from counts of their nocturnal calls in Santo Antão, São Vicente, Santa Luzia, Branco, Raso and São Nicolau. Cape Verde Petrel occurred only on mountainous islands (Santo Antão, São Nicolau, Santiago, and Fogo) from mid-to high elevations. Larger species such as the Cape Verde Shearwater and Boyd’s Shearwater exhibited a wider distribution in the archipelago, occurring close to the coastline but at lower densities on populated islands. Small procellariforms such as the Cape Verde Storm-petrel occurred at high densities only on rat-free islets and in steep areas of main islands where introduced cats and rats are unlikely to occur. The main threats to seabird populations in Cabo Verde range from predation by introduced predators, habitat alteration or destruction, and some residual human persecution.

Carry-over effects from one stage of the annual cycle to subsequent stages can have profound effects on individual fitness. In migratory birds, much research has been devoted to examining such effects from the nonbreeding to the breeding period. We investigated potential carry-over effects influencing spring body condition, breeding phenology, and performance for 3 species of sympatric, declining Nearctic–Neotropical migratory swallows: Bank Swallow (Riparia riparia), Barn Swallow (Hirundo rustica), and Cliff Swallow (Petrochelidon pyrrhonota). To examine carry-over effects, we used structural equation modeling and several intrinsic markers, including stable isotope (δ 2H, δ 13C, and δ 15N) and corticosterone (CORTf) values from winter molted-feathers, and changes in telomere length between breeding seasons. We found support for carry-over effects for all 3 species, however, the specific relationships varied between species and sexes. Effects leading to lower breeding performance were only observed in male Bank, female Barn, and female and male Cliff Swallows. In most cases, carry-over effects were attributed to differences in stable isotope values (most commonly with δ 2H) presumably related to differences in winter habitat use, but, for Cliff Swallows, negative carry-over effects were also linked to higher CORTf values and greater rates of telomere shortening. This work provides further support for the potential role of nonbreeding conditions on population declines, and indicates how multiple intrinsic markers can be used to provide information on ecological conditions throughout the annual cycle.

No abstract

Although communal roosting during the wintering and migratory periods is well documented, few studies have recorded this behavior during the breeding season. We used automated radio telemetry to examine communal roosting behavior in breeding Bank Swallow (Riparia riparia) and its relationship with biological and environmental factors. Specifically, we used (generalized) linear mixed models to determine whether the probability of roosting communally and the timing of departure from and arrival at the colony (a measure of time away from the nest) was related to adult sex, nestling age, brood size, nest success, weather, light conditions, communal roosting location, and date. We found that Bank Swallow individuals roosted communally on 70 ± 25% of the nights, suggesting that this behavior is common. The rate of roosting communally was higher in males than in females with active nests, increased with older nestlings in active nests, and decreased more rapidly with nestling age in smaller broods. Together, these results suggest that that communal roosting is limited by the thermoregulatory needs of the offspring. The rate of roosting communally and the total time spent away from the nest while roosting also decreased with humidity and low temperatures (total time only), supporting the conclusion that the thermoregulatory needs of both offspring and adults limit this behavior. Communal roosting was also restricted to dark nights, suggesting that the Bank Swallow may roost communally to avoid predation. Individuals also roosted communally and spent more time at the roosts as the breeding season progressed, suggesting that communal roosting may be a way of avoiding the growing number of ectoparasites at the colony or taking advantage of prospecting opportunities in the morning. The Bank Swallow is listed as Threatened in Canada, so understanding the factors that relate to communal roosting is essential for identifying the critical habitat of this declining species. Facteurs biologiques et environnementaux liés au comportement de nidification communautaire de l'hirondelle de rivage (Riparia riparia) pendant la saison de reproductionRÉSUMÉ. Bien que la nidification communautaire au cours des périodes d'hivernage et de migration soit bien documentée, rares sont les études qui ont enregistré ce même comportement au cours de la saison de reproduction. Nous avons utilisé la radio-télémétrie automatisée pour examiner le comportement de nidification communautaire de l'hirondelle de rivage (Riparia riparia) en période de reproduction et sa relation avec les facteurs biologiques et environnementaux. Plus précisément, nous avons (généralement) utilisé des modèles linéaires mixtes pour déterminer si la probabilité de nidification communautaire et le moment du départ et de l'arrivée dans la colonie (permettant de mesurer le temps passé en dehors du nid) était liée au sexe chez les adultes, à l'âge de nidification, à la taille de la couvée, à l'efficacité du nid, aux conditions météorologiques, à l'emplacement du nid collectif et à la...

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.