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Variation in offspring sex ratio, particularly in birds, has been frequently studied over the last century, although seldom using long-term monitoring data. In raptors, the cost of raising males and females is not equal, and several variables have been found to have significant effects on sex ratio, including food availability, parental age, and hatching order. Sex ratio differences between island populations and their mainland counterparts have been poorly documented, despite broad scientific literature on the island syndrome reporting substantial differences in population demography and ecology. Here, we assessed individual and environmental factors potentially affecting the secondary sex ratio of the long-lived Egyptian vulture Neophron percnopterus. We used data collected from Spanish mainland and island populations over a ca. 30-year period (1995-2021) to assess the effects of insularity, parental age, breeding phenology, brood size, hatching order, type of breeding unit (pairs vs. trios), and spatial and temporal variability on offspring sex ratio. No sex bias was found at the population level, but two opposite trends were observed between mainland and island populations consistent with the island syndrome. Offspring sex ratio was nonsignificantly female-biased in mainland Spain (0.47, n = 1112) but significantly male-biased in the Canary Islands (0.55, n = 499), where a male-biased mortality among immatures could be compensating for offspring biases and maintaining a paired adult sex ratio. Temporal and spatial variation in food availability might also have some influence on sex ratio, although the difficulties in quantifying them preclude us from determining the magnitude of such influence. This study shows that insularity influences the offspring sex ratio of the Egyptian vulture through several processes that can affect island and mainland populations differentially. Our research contributes to improving our understanding of sex allocation theory by invest

Birds striking aircrafts cause substantial economic loss world-wide and, more worryingly, human and wildlife fatalities. Designing effective measures to mitigate fatal bird strikes requires an in-depth knowledge of the characteristics of this incident type and the flight behaviours of the bird species involved. The characteristics of bird strikes involving aircraft crashes or loss of human life in Spain were studied and compared to flight patterns of birds monitored by GPS. We tracked 210 individuals of the three species that cause the most crashes and human fatalities in Spain: griffon and cinereous vultures Gyps fulvus and Aegypius monachus and white storks Ciconia ciconia. All the crashes involved general aviation aircrafts, while none were recorded in commercial aviation. Most occurred outside airport boundaries, at midday, and in the warmest months, which all correspond with the maximum flight activity of the studied species. Bird flight altitudes overlapped the legal flight altitude limit set for general aviation. Policy implications. Mitigation of fatal bird strikes should especially address the conflict between general aviation and large soaring birds. Air transportation authorities should consider modifying the flight ceiling for general aviation flights above the studied species' maximum flight altitude. Moreover, policymakers should issue pilots with recommendations regarding the dates and times of peak activity of large soaring bird species to improve flight safety.

Despite increasing work detailing the presence of foraging specializations across a range of taxa, limited attention so far has been given to the role of spatiotemporal variation in food predictability in shaping individual resource selection. Here, we studied the exploitation of human-provided carrion resources differing in predictability by Canarian Egyptian vultures (Neophron percnopterus majorensis). We focussed specifically on the role of individual characteristics and spatial constraints in shaping patterns of resource use. Using high-resolution GPS data obtained from 45 vultures tracked for 1 year, we show that individual vultures were repeatable in both their monthly use of predictable and semipredicable resources (feeding station vs. farms) and monthly levels of mobility (home range size and flight activity). However, individual foraging activities were simultaneously characterized by a high degree of (temporal) plasticity in the use of the feeding station in specific months. Individual rank within dominance hierarchy revealed sex-dependent effects of social status on resource preference in breeding adults, illustrating the potential complex social mechanisms underpinning status-dependent resource use patterns. Our results show that predictable food at feeding stations may lead to broad-scale patterns of resource partitioning and affect both the foraging and social dynamics within local vulture populations.

The study of animal movement makes possible to understand how the spatial context influences individuals and populations, something especially important for species with high movement abilities able to wander routinely over large areas and face diverse humanmediated threats at different spatial scales. Vultures are long-lived scavenging vertebrates with delayed maturity and low fecundity, often exhibiting complex social behaviours. European and most of the Old World vulture populations have been historically dependent on the spatial distribution of human-provided resources. Currently, they are endangered worldwide suffering regional dramatic declines of up to 90% mainly provoked by direct and indirect persecution, infrastructure development and decrease in food resources. Effective vulture conservation requires spatially-explicit understanding of how vultures cope with resource availability and human induced transformation. In this thesis, we used spatial data collected between 2013 and 2018 from 49 GPStagged Canarian Egyptian vultures (Neophron percnopterus majorensis). The bulk of this endemic subspecies is concentrated in Fuerteventura Island where it depends on extensive goat farms, currently changing towards semi-intensive and intensive regimes. In addition, it suffers from high mortality in power lines. Movement information is combined with individual characteristics, life-history stages, and detailed data on the spatial distribution of territories, feeding resources, and human facilities. Particularly, we examined i) drivers of the use of power lines, ii) foraging tactics according to spatiotemporal variation in food predictability and individual characteristics, iii) drivers of use of livestock farms, and iv) farmers’ perception about the target species in relation to the observed spatial behaviour. Vultures’ behaviour was influenced by the distribution, predictability and amount of feeding resources, as well as by the spatial distribution of conspecifics an

This dataset was used to analyze survival probabilities of Egyptian Vultures at Canary Islands from 1998 to 2017.