Diet composition and foraging behaviour may show considerable variation among population groups (such as sex- and age-classes), with potentially important consequences for population dynamics. Thus, failure to account for within-species differences in trophic ecology can bias our understanding of different aspects of population ecology and limit the implementation of effective management and conservation strategies. Although countless studies have investigated the diet of birds, comparatively few have tried to describe intraspecific sources of dietary variation. Here, we used stable isotope analysis (SIA) to investigate sex- and age-related dietary segregation in the lesser kestrel (Falco naumanni) breeding in South Iberia and to discuss potential mechanisms involved in such segregation. Females had a narrower isotopic niche width and significantly more depleted δ1339 C signatures than males during the courtship period, likely due to a higher consumption of energetically rich mole crickets. Our results suggest that sex-specific differences in the diet of lesser kestrels do not result from intra-specific competition and are unlikely to be explained by sexual size dimorphism alone. Instead, the main driving force of observed sexual segregation appears to be the different energetic requirements of males and females before laying, when females need a higher allocation of resources to egg production. δ1545 N isotopic signatures differed significantly between adults and chicks and niche overlap between these age classes was low. Stable isotopic mixing models (SIAR) showed that, compared to adults, the diet of chicks was less diverse and mainly dominated by grasshoppers. Different resource allocation between chicks and adults might also result from different energy requirements, as rapidly growing chicks require 50 more energy than adults, ultimately leading to a parent-offspring dietary segregation. Finally, overall agreement between pellet analysis and SIA methods highlight the potential of SIA for assessing intra-specific variation in dietary regimes which is often unfeasible through conventional approaches of diet assessment

Small-sized nocturnal Procellariiformes are abundant predators in oceanic areas worldwide and are thought to play an important role in many marine food webs as consumers of superabundant mesopelagic prey. However, the spatial ecology and foraging behaviour of the great majority of these species remain largely unknown. We studied the non-breeding distribution and at-sea activity of a migratory small-sized Procellariiform, the Bulwer's petrels Bulweria bulwerii, from the Selvagem Island colony (subtropical Northeast Atlantic). We found that soon after breeding Bulwer's petrels migrate towards deep (mean depth of 4416 m), open oceanic waters of the tropical Atlantic, spending the winter far from shelf and shelf-break areas, on regions avoided by most other avian migrants in the Atlantic. When at sea, Bulwer's petrels spent more time flying during the night ([90 %, all year round) than any other seabird studied so far. This nighttime activity was not influenced by the lunar cycle, suggesting that this highly specialised nocturnal seabird is probably very well adapted to locating and capturing prey even in very dark conditions. The results from the present study may have important implications for the identification of important bird areas in the marine realm, whose boundaries have been delineated so far mostly on the basis of the distribution and behaviour of better studied medium-to large-sized seabirds.Keywords At-sea activity Á Bulwer's petrels Á Migration Á Procellariiformes Á Seabirds Zusammenfassung Wanderer ü ber der Tiefsee: Zugverhalten und Verbreitung des hochgradig pelagischen Bulwersturmvogels

Islands worldwide have suffered seabird extinctions after the arrival of humans and the alien species they introduced. On Santa Luzia (Cabo Verde), an uninhabited island of 35 km 2 , the presence of an impressive quantity of petrel bones in coastal dunes suggested the previous existence of an important seabird colony. Yet, these remains had not been identified and no seabird extinctions have been reported for the island. This paper characterizes the extinct seabird colony of Santa Luzia and discusses the chronology and possible causes of its demise. A total of 130 grid points in a 5 km 2 area and 38 supplementary points within and outside the main study area were excavated to collect bone remains. A total of 1318 anatomical elements, identified as White-faced Storm Petrel Pelagodroma marina eadesorum (85.3% of the minimum number of individuals, MNI), Boyd's Shearwater Puffinus lherminieri boydi (11.8% MNI) and Cape Verde Storm Petrel Hydrobates jabejabe (2.9% MNI), were found in 18% of the sampling points, within 1.25 km 2 . Neither of the two former species currently breeds on Santa Luzia. In addition, two bones of the Cape Verde Shearwater Calonectris edwardsii and Pterodroma sp. were detected in the supplementary points. Radiocarbon dating of White-faced Storm Petrel (n = 10) and Boyd's Shearwater bones (n = 13) suggests that the colony probably went extinct during the first half of the twentieth century. The recent extinction of these species on Santa Luzia might be consequent on the arrival of humans and their domestic animals on the island. We estimate that the extinct seabird populations must have been at least hundreds of thousand strong, far larger than current populations of the same species in Cabo Verde. We suggest that, following feral cat eradication, Santa Luzia has a significant potential for seabird restoration. KeywordsBones • Fossils • Radiocarbon • Petrel • Cape Verde • Extinction Zusammenfassung Beschreibung einer erloschenen Seevogelkolonie auf der Insel Santa Luzia (Kap Verde) und deren Potenzial für zukünftige Wiederansiedlungen Weltweit kam es auf Inseln nach der Ankunft des Menschen und den durch diesen eingeführten fremden Arten zum Aussterben von Seevögeln. Auf Santa Luzia (Kap Verde), einer 35 km 2 großen unbewohnten Insel, deutet das Vorhandensein einer beeindruckenden Menge an Sturmvogelknochen in den Küstendünen auf die ehemalige Existenz einer bedeutenden Seevogelkolonie hin. Bislang waren diese Funde aber noch unbestimmt, und es waren keine Aussterbeereignisse von Seevögeln von dieser Insel bekannt. In diesem Beitrag beschreiben wir die erloschene Seevogelkolonie auf Santa Luzia und diskutieren Chronologie und mögliche Ursachen ihres Verschwindens. An insgesamt 130 Rasterpunkten in einem 5 Communicated by C. Barbraud.

The White-faced Storm Petrel (WFSP) Pelagodroma marina has a widespread distribution, although virtually nothing is known about their feeding ecology and distributions at-sea. To describe their foraging areas, a total of 77 birds were equipped with 1 g-GPS loggers on Selvagem Grande, Madeira, Portugal (30° 09′ N, 15° 52′ W), during the 2018 and 2019 breeding seasons. We also assessed the diet of WFSP by analysing 17 faecal samples from chicks and 1 regurgitation from an adult using DNA metabarcoding techniques. Additionally, we collected body feathers from ten WFSP chicks to determine mercury concentration. WFSP fed mainly in deep oceanic waters, travelling up to 400 km from the colony, and did not concentrate in any well-defined, population-level foraging hotspots. Some individuals foraged along the edge of the shelf, near the African coast and the Canary Islands, especially during chick rearing. The duration of foraging trips and the total distance travelled, were, on average, 5.1 days and 723 km during the incubation period and 3.0 days and 578 km during chick rearing. The diet of WFSP was dominated by fish and cephalopods (crustacean prey were not detected), with Myctophidae (FO = 71%) representing the main fish family. WFSP often consume mesopelagic fish, in line with their preference for deep oceanic waters and with a small difference in at sea behavior (i.e., travel speed) between the diurnal and nocturnal period. The relatively high concentrations of mercury accumulated in body feathers of WFSP chicks (3.45 ± 1.44 mg kg −1 dry weight; range 1.68-6.01 mg kg −1 ) support the idea that WFSP raise their chicks mostly on mesopelagic prey from deep pelagic areas.

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.