The foraging areas used by adult Sooty Terns Onychoprion fuscatus during incubation and early chick-rearing on Bird Island, Seychelles, were investigated using small GPS loggers. Birds departed the colony mainly during the night and foraged by day. Most foraging trips were completed within 24 hr, but during incubation the longest duration recorded was seven days and 14 hr (during which the bird travelled 2,783 km and reached a maximum of 692 km from the colony). Departures were generally in an arc from south (180 degrees) through westerly to 40 degrees. Sooty Terns foraged frequently in waters over the Seychelles Bank shelf break, but some birds travelled further, including to the area around the Coco-de-Mer Ridge ca. 400 km north of Bird Island. In the four days after hatching, adult foraging trips tended to be shorter, within 24 hr, and the small sample of tracks obtained revealed that they potentially foraged over deeper areas. Most of the foraging areas identified were within the Seychelles' Exclusive Economic Zone, with some foraging areas occurring outside the Seychelles marine protected areas.

Abstract Understanding how demographic rates change during population recovery is critical for evaluating conservation success and determining when populations become self‐sustaining. However, documenting such transitions requires long‐term monitoring across substantial changes in population size— conditions that are rarely met. We leverage a 29‐year capture‐mark‐recapture dataset from the echo parakeet population ( Alexandrinus eques ), a vulnerable endemic parrot of Mauritius island that recovered from fewer than 20 individuals to over 500 during the study period. Using multistate capture‐mark‐recapture models, we analysed encounter histories of 2734 known‐aged wild individuals to estimate age and state‐specific survival probabilities while accounting for temporal variation, transitions between breeding states and controlling for unequal recapture probabilities. Demographic rates changed substantially during population recovery. Recruitment into the breeding population declined across all age classes as the population approached carrying capacity. Survival showed contrasting patterns: juveniles (<2 years old) exhibited a declining temporal trend (from 0.68 in 1994 to 0.57 in 2020), whereas adult survival remained stable across years, with breeding adults showing consistently higher rates (0.96–0.97) than non‐breeding individuals (0.76–0.90). Synthesis and applications . These findings highlight the dynamic nature of demographic processes throughout population recovery and emphasise the value of continued monitoring beyond apparent recovery to detect density‐dependent shifts in demographic rates of wildlife populations.

Abstract Inbreeding depression (the reduction in fitness associated with inbreeding) has been demonstrated in a wide range of animals, but despite its ubiquity, is not an inevitable consequence of inbreeding. As a result, there is uncertainty about the extent to which inbreeding depression poses an ongoing risk to endangered species currently experiencing significant demographic recovery. Quantifying inbreeding depression will be critical if we want to understand these risks. A comprehensive quantification of the fitness costs of inbreeding requires detailed individual-based longitudinal data so lifetime impacts can be assessed. Here, we use an extraordinarily detailed long-term dataset on Mauritius kestrels ( Falco punctatus ) to explore inbreeding depression in a population currently experiencing significant demographic recovery. To do so, we constructed a social pedigree of 1,758 individuals and combined this with 1,240 nest records and 1,411 individual resighting histories to explore lifetime fitness effects over a 30-year period. Inbreeding increased significantly over time as the population recovered before stabilising. Inbred eggs were less likely to survive to fledging. Inbred adult male and female birds had significantly lower annual reproductive success than outbred individuals because of a lower annual egg-to-fledgling survival probability. This resulted in significantly lower lifetime reproductive success in inbred females but not males, which showed a negative trend. Population growth was negative and extinction risk increased slightly at current levels of inbreeding. These impacts will become more severe should inbreeding levels increase in the future, which is highly likely given ongoing genomic erosion. Taken together, our results demonstrate significant fitness costs associated with inbreeding in Mauritius kestrels, which pose an ongoing risk to population viability. This suggests that monitoring and managing inbreeding risks in endangered species will likely be required even in populations that are showing significant demographic recovery in response to conservation interventions.

The accurate identification of foraging locations is critical for wildlife conservation. While remote sensing and biologging devices provide much of the necessary data, their deployment is often complicated by factors such as weight, battery life and sensor capacity, limiting their effectiveness for long-term tracking of wide-ranging species. In this study, we evaluate the effectiveness of saltwater immersion data from light-level geolocation loggers (global location sensor; GLS) as a predictor of foraging behaviour in a pursuit-diving seabird, the red-footed booby (Sula sula rubripes). Using co-deployed tri-axial acceleration data as a high-resolution benchmark, we compare the performance of deep learning models for classifying dive and non-dive states. Predictions are cross-validated on withheld individuals for generalizability. Using a small pilot dataset, we find that models trained solely on GLS data only slightly underperform those trained on acceleration data despite the resolution discrepancy, classifying the diving behaviours of unseen birds with 93.65% accuracy. These findings suggest that GLS data alone may be sufficient to reliably infer dive events and, by extension, foraging locations, for pursuit-diving seabirds, providing a minimally invasive, scalable method to enrich year-round GLS migratory tracking studies using models derived from co-deployment of GLS and global positioning system devices.

Global calls for greater ocean protection have sparked renewed interest in very large marine protected areas (VLMPAs, >100,000 km 2 ) to achieve management targets; however, their conservation value is debated. We assessed the suitability of a VLMPA (640,000 km 2 ) in the Indian Ocean for capturing the movements of resident mobile marine megafauna. We found that 95% of foraging, breeding and/or locally migrating individuals occurred within the VLMPA despite variable habitat use; adult hawksbill turtles ( Eretmochelys imbricata , n = 22, 6124 tracking days) foraged on mesophotic banks (>30 m depth), reef manta rays ( Mobula alfredi , n = 23, 652 tracking days) used shallow submerged banks, and seabirds (red‐footed boobies Sula sula , brown boobies Sula leucogaster , wedge‐tailed shearwaters Ardenna pacifica , n = 257, 1084 tracking days) collectively foraged throughout coastal to pelagic waters. To understand the size of MPA necessary to encompass resident mobile species, we assessed overlap with smaller and larger hypothetical MPAs. An MPA meeting the minimum threshold of a VLMPA (>100,000 km 2 ) would encompass 97% of manta and 94% of turtle locations, and 59% of all seabird locations because of their more pelagic distribution. Synthesis and applications . Our results provide clear evidence for the value of the large scale of the Chagos Archipelago very large marine protected area for protection of taxonomically diverse mobile megafauna. Further, we highlight the value of the VLMPA approach as a strategy towards achieving 30% ocean protection by 2030.

When navigating homewards, central-place foragers can use landmarks and sun angle to adjust their return movement behaviour. However, for tropical oceanic species foraging from low-lying atolls, the effectiveness of their homing journeys on their time returns remains unclear. Thus, in this study, the navigation behaviour of red-footed boobies, Sula sula rubripes, in the Chagos Archipelago, central Indian Ocean, was investigated. Using GPS tracking data from 207 breeding adults across four colonies, the homing duration, bearing and trajectory straightness during central-place foraging were explored to elucidate the navigational constraints and temporal dynamics. Return distances and orientations were modelled in relation to the time of day and distance to the colony to assess whether birds adjust their homing behaviour to return before dusk. We found that red-footed boobies navigated efficiently back to their colony on fast, straight and direct flights and adjusted their homing behaviour to arrive at the colony around dusk: the closer to the evening twilight they start their homing journey, the shorter, faster and more direct their routes become. These findings provide a comprehensive understanding of seabird navigation in tropical environments, as well as insights into the adaptive mechanism underlying successful navigation over expansive oceanic territories. (c) 2025 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Understanding how the behaviour of volant species is influenced by winds is important at a time when global airflow patterns and intensities are shifting. We investigated how wind speeds and directions influenced the flight and feeding events of a flap-gliding seabird during central place trips searching for aerial prey like Exocoetidae flying fish. We deployed GPS accelerometers on red-footed boobies ( Sula sula rubripes ) in the Chagos Archipelago (Indian Ocean) for 45 foraging trips. By comparing foraging commutes to simulated alternative routes, we demonstrate that birds preferentially selected tailwinds and crosswinds, with stronger selection during the outbound compared with the inbound leg. By selecting favourable winds, birds reached higher ground speeds without having to increase flapping flight. Selecting favourable wind conditions may be an adaptation to tropical pelagic habitats and ephemeral prey. Hidden Markov models, used to characterize behavioural states, revealed that birds were more likely to forage during windier conditions, perhaps aided by increased accessibility of flying fish—which a small sub-sample of bird-borne video cameras revealed were largely caught on the wing. We therefore show how wind has divergent consequences for foraging journeys and feeding events, with implications for understanding the ecological effects of climate change-driven wind alterations.

Aim Knowledge of the main drivers of population differentiation is crucial for understanding evolutionary processes and preserving biodiversity. While primarily studied in terrestrial habitats, the mechanisms operating in the marine realm are less well understood. This study reconstructed the phylogeographic history of a tropical seabird to identify relevant marine barriers promoting intraspecific diversity in the Western Indian Ocean. Location Western Indian Ocean. Taxon Three subspecies of tropical shearwater: Puffinus bailloni bailloni , P. b. nicolae, P. b. colstoni. Methods We used restriction site-associated DNA sequencing and applied population genomics to birds from six breeding colonies to assess intraspecific diversity, population genetic structure and connectivity in the tropical shearwater. Results were complemented with data from six oceanographic variables and effective migration surfaces to evaluate the role of oceanographic factors in driving population differentiation. Results All analyses consistently separated the birds from the northern colonies (subsp. nicolae and colstoni) from those of the southern islands (subsp. bailloni), but failed to assign the colstoni birds as a different taxon. Results revealed remarkable levels of genetic differentiation within an ocean basin in a highly vagile species and suggested higher levels of gene flow at the northern limit of the species' distribution compared to the southern range. Main Conclusions Our study suggests that ocean surfaces and sea surface temperature may constitute an important barrier to gene flow for the tropical shearwater and potentially other marine species in the region. This study does not support the colstoni form as a different subspecies, highlighting the need for further taxonomic reassessment. Ultimately, the results allowed us to identify Europa and Aldabra as the most threatened management units and propose conservation strategies directly applicable to these most at-risk colonies.

Aim: To identify the broad-scale oceanic migration routes ('marine flyways') used by multiple pelagic, long-distance migratory seabirds based on a global compilation of tracking data. Location: Global. Time Period: 1989-2023. Major Taxa Studied: Seabirds (Families: Phaethontidae, Hydrobatidae, Diomedeidae, Procellariidae, Laridae and Stercorariidae). Methods: We collated a comprehensive global tracking dataset that included the migratory routes of 48 pelagic and long-distance migrating seabird species across the Atlantic, Indian, Pacific and Southern Oceans. We grouped individuals that followed similar routes, independent of species or timings of migration, using a dynamic time warping clustering approach. We visualised the routes of each cluster using a line density analysis and used knowledge of seabird spatial ecology to combine the clusters to identify the broad-scale flyways followed by most pelagic migratory seabirds tracked to-date at an ocean-basin scale. Results: Six marine flyways were identified across the world's oceans: the Atlantic Ocean Flyway, North Indian Ocean Flyway, East Indian Ocean Flyway, West Pacific Ocean Flyway, Pacific Ocean Flyway and Southern Ocean Flyway. Generally, the flyways were used bidirectionally, and individuals either followed sections of a flyway, a complete flyway, or their movements linked two or more flyways. Transhemispheric figure-of-eight routes in the Atlantic and Pacific oceans, and a circumnavigation flyway in the Southern Ocean correspond with major wind-driven ocean currents. Main Conclusions: The marine flyways identified demonstrate that pelagic seabirds have similar and repeatable migration routes across ocean-basin scales. Our study highlights the need to account for connectivity in seabird conservation and provides a framework for international cooperation.

Monitoring animal populations is crucial for assessing the health of ecosystems. Traditional methods, which require extensive fieldwork, are increasingly being supplemented by time-lapse camera-trap imagery combined with an automatic analysis of the image data. The latter usually involves some object detector aimed at detecting relevant targets (commonly animals) in each image, followed by some postprocessing to gather activity and population data. In this paper, we show that the performance of an object detector in a single frame of a time-lapse sequence can be improved by including spatio-temporal features from the prior frames. We propose a method that leverages temporal information by integrating two additional spatial feature channels which capture stationary and non-stationary elements of the scene and consequently improve scene understanding and reduce the number of stationary false positives. The proposed technique achieves a significant improvement of 24% in mean average precision (mAP@0.05:0.95) over the baseline (temporal feature-free, single frame) object detector on a large dataset of breeding tropical seabirds. We envisage our method will be widely applicable to other wildlife monitoring applications that use time-lapse imaging.

Many species of seabirds are threatened and understanding their at-sea distributions during breeding is a priority for their conservation. Recent developments in tracking technology, data analytical frameworks and tools are proving invaluable in the identification of at-sea areas of high use and hence conservation importance, which can be used to inform marine spatial planning. However, the outputs from these frameworks and tools are contingent on the underlying tracking data, which are shaped by the myriad of decisions made when designing and implementing a tracking program. These decisions include breeding colony choice and identification of areas (sub-colonies) within the colony in which to deploy tracking devices. However, our understanding of the consequences of this on the resulting tracking data and hence identification of at-sea priority areas is limited and rarely considered. In April 2022 we tracked 196 foraging trips of 54 breeding red-footed boobies (Sula sula) at two sub-colonies (1.5 km apart) on South Island, Farquhar Atoll in south-west Seychelles. We found that foraging trip distance and duration did not differ between the two sub-colonies, but trip orientation did: resulting in sub-colony segregation at sea predominantly to the north and south of the atoll with consequences for the identification of at-sea areas of high use. Our findings indicate that sub-colony variation in at-sea distribution of breeding seabirds may be more commonplace than current research suggests and if our tracking program had involved only one sub-colony then key outputs which could serve towards marine spatial planning efforts may be biased.

Comprehending how environmental variability shapes foraging behaviour across habitats is key to unlocking insights into consumer ecology. Seabirds breeding at high latitudes are exemplars of how marine consumers can adapt their behaviours to make use of predictable foraging opportunities, but prey tends to be less predictable in tropical oceanic ecosystems and may require alternative foraging behaviours. Here we used GPS and time-depth recorder loggers to investigate the foraging behaviour of central placed adult red-footed boobies (Sula sula rubripes), a tropical seabird that forages in oceanic waters via diving, or by capturing aerial prey such as flying fish in flight. Dive bout dynamics revealed that red-footed boobies appeared to exploit denser, but more sparsely distributed prey patches when diving further from the colony. Furthermore, although we found no evidence of environmentally driven habitat selection along their foraging routes, red-footed boobies preferentially dived in areas with higher sea surface temperatures and chlorophyll-a concentrations compared to conditions along their foraging tracks. This multi-scale variation implies that habitat selection differs between foraging routes compared to dive locations. Finally, red-footed booby dives were deepest during the middle of the day when light penetration was greatest. Ultimately, we highlight the importance of gaining insights into consumer foraging across different ecosystems, thereby broadening understanding of how animals might respond to changing environmental conditions.

Effective seabird conservation requires understanding their marine spatial ecology. Tracking can reveal details of their foraging ecology and habitat use, as well as the suitability of marine protected areas for at-sea conservation, but results are often regionally specific. Here we characterised the foraging behaviour of tropical breeding brown boobies Sula leucogaster in the Chagos Archipelago, Western Indian Ocean, and tested habitat requirements. GPS tracking of thirteen individuals from two colonies, located 142 km apart on the same atoll (Great Chagos Bank), showed similar foraging effort and habitat preferences despite differences in season and breeding stage. Brown boobies from both tracked populations foraged close to the colony along the atoll shelf edge, avoiding deep oceanic areas and shallow waters of the Great Chagos Bank atoll, but within the Chagos Archipelago Marine Protected Area. Sea-level height anomaly and sea surface temperature were important foraging predictors at both sites, although birds experienced distinct environmental conditions between colonies. These results suggest that while brown boobies have colony-specific at-sea foraging areas, similarities in habitat drivers of distribution and foraging behaviour can inform predictions of distributions at other colonies within the archipelago, with important benefits for at-sea conservation efforts.

Humans are regularly cited as the main driver of current biodiversity extinction, but the impact of historic volcanic activity is often overlooked. Pre-human evidence of wildlife abundance and diversity are essential for disentangling anthropogenic impacts from natural events. Réunion Island, with its intense and well-documented volcanic activity, endemic biodiversity, long history of isolation and recent human colonization, provides an opportunity to disentangle these processes. We track past demographic changes of a critically endangered seabird, the Mascarene petrel Pseudobulweria aterrima, using genome-wide SNPs. Coalescent modeling suggested that a large ancestral population underwent a substantial population decline in two distinct phases, ca. 125,000 and 37,000 years ago, coinciding with periods of major eruptions of Piton des Neiges. Subsequently, the ancestral population was fragmented into the two known colonies, ca. 1500 years ago, following eruptions of Piton de la Fournaise. In the last century, both colonies declined significantly due to anthropogenic activities, and although the species was initially considered extinct, it was rediscovered in the 1970s. Our findings suggest that the current conservation status of wildlife on volcanic islands should be firstly assessed as a legacy of historic volcanic activity, and thereafter by the increasing anthropogenic impacts, which may ultimately drive species towards extinction.

The over‐exploitation of wild birds and the products derived from them can be a key threat driving changes in bird species richness and abundance. However, inadequate information on harvest levels combined with irregular population monitoring often means that the role of harvesting in population decline is difficult to quantify. Historically, the pan‐tropical Sooty Tern Onychoprion fuscatus has been subjected to extensive egg harvesting, yet the role of sustained harvesting in population change and future population viability remains unclear. In this study, we used published and new estimates of key demographic rates for a large, harvested Sooty Tern population in Seychelles, western Indian Ocean, to run a series of population viability analyses. We retrospectively assess the impact of historical levels of egg harvesting, and also predict how this population may respond under different future harvesting regimes, assuming no additional environmental change. We provide evidence that egg harvesting has played a substantial role in driving the population decline of Sooty Terns to date and demonstrate that continued harvesting will probably lead to further, possibly dramatic, declines in population size. These results indicate that recent levels of egg harvesting in Seychelles are not sustainable. We also show that the life‐history strategy of Sooty Terns, including a delayed age of first breeding, means the current 2‐year local moratorium on egg harvesting is unlikely to generate an observable population‐level response in Seychelles. Instead, we recommend that the current moratorium is extended at least beyond the age of first breeding (i.e. 5 years) to support appropriate evaluation. We additionally show that harvesting Sooty Tern eggs at much lower levels, i.e. 10% of the population size, is unlikely to reverse population decline. Therefore, long‐term egg harvesting strategies require careful evaluation to maintain a balance between the social, commercial, cultural and biodiversity significance of Sooty Terns in Seychelles.

Bio‐logging has revealed much about high‐latitude seabird migratory strategies, but migratory behaviour in tropical species may differ, with implications for understanding nutrient deposition. Here we use combined light‐level and saltwater immersion loggers to study the year‐round movement behaviour of adult red‐footed boobies Sula sula rubripes from the Chagos Archipelago, tropical Indian Ocean, to assess migratory movements and estimate nutrient deposition rates based on the number of days they spent ashore. Light levels suggest that red‐footed boobies are resident in the Chagos Archipelago year‐round, although there are large latitudinal errors this close to the equator. Immersion data also indicate residency with tracked birds returning to land every one or two days. Spending an average of 79.86 ± 2.80 days and 280.84 ± 2.64 nights per year on land allows us to estimate that the 21 670 pairs of red‐footed boobies deposit 37.34 ± 0.56 tonnes year−1 of guano‐derived nitrogen throughout the archipelago. Our findings have implications for tropical seabird conservation and phylogenetics, as well as for assessing the impact of seabird nutrients on coral reef ecosystems.

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.

Conservation of breeding seabirds typically requires detailed data on where they feed at sea. Ecological niche models (ENMs) can fill data gaps, but rarely perform well when transferred to new regions. Alternatively, the foraging radius approach simply encircles the sea surrounding a breeding seabird colony (a foraging circle), but overestimates foraging habitat. Here, we investigate whether ENMs can transfer (predict) foraging niches of breeding tropical seabirds between global colonies, and whether ENMs can refine foraging circles. We collate a large global dataset of tropical seabird tracks (12000 trips, 16 species, 60 colonies) to build a comprehensive summary of tropical seabird foraging ranges and to train ENMs. We interrogate ENM transferability and assess the confidence with which unsuitable habitat predicted by ENMs can be excluded from within foraging circles. We apply this refinement framework to the Great Barrier Reef (GBR), Australia to identify a network of candidate marine protected areas (MPAs) for seabirds. We found little ability to generalise and transfer breeding tropical seabird foraging niches across all colonies for any species (mean AUC: 0.56, range 0.4-0.82). Low global transferability was partially explained by colony clusters that predicted well internally but other colony clusters poorly. After refinement with ENMs, foraging circles still contained 89% of known foraging areas from tracking data, providing confidence that important foraging habitat was not erroneously excluded by greater refinement from high transferability ENMs nor minor refinement from low transferability ENMs. Foraging radii estimated the total foraging area of the GBR breeding seabird community as 2,941,000 km2, which was refined by excluding between 197,000 km2 and 1,826,000 km2 of unsuitable foraging habitat. ENMs trained on local GBR tracking achieved superior refinement over globally trained models, demonstrating the value of local tracking. Our framework demonstrates an effective method to delineate candidate MPAs for breeding seabirds in data-poor regions.

Colonial animals experience density-dependent competition for food, which is posited to influence foraging range and lead to inter-colony segregation. However, such patterns are poorly studied in the tropics, where predictable day lengths, oligotrophic conditions, and facultative foraging may alter the relationships between foraging and intra-specific competition. Here, we GPS-tracked 207 breeding red-footed boobies Sula sula rubripes (RFB) from 4 neighbouring Chagos Archipelago colonies (~1100 to 9200 breeding pairs) in the central Indian Ocean, to determine how foraging strategies (i.e. effort, segregation, and timing) vary with colony, while accounting for sex, monsoon season, stage of reproduction, year, and individual. During incubation and chick-rearing, RFBs commute to pelagic foraging grounds (maximum distance mean ± SE: 112.9 ± 3.7 km; total distance: 298.4 ± 6.2 km) over 1 to 5 d (18.5 ± 1.6 h). Foraging effort was highest at the largest colony, and greater among females than males. Departure angles varied among colonies, leading to foraging areas that were largely spatially segregated. Timing of departures and arrivals were strongly constrained by daylight hours, although females and birds at the largest colony left earliest. Our study highlights the importance of inter-colony differences in tropical seabird foraging, which may relate to different levels of intra-specific competition. Moreover, links between foraging times and colony size suggest a previously undescribed outcome of density-dependent competition, highlighting the importance of understanding colonial living across multiple dimensions.