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Avian perching maneuvers are one of the most frequent and agile flight scenarios, where highly optimized flight trajectories, produced by rapid wing and tail morphing that generate high angular rates and accelerations, reduce kinetic energy at impact. While the behavioral, anatomical, and aerodynamic factors involved in these maneuvers are well described, the underlying control strategies are poorly understood. Here, we use optimal control methods on an avian-inspired drone with morphing wing and tail to test a recent hypothesis derived from perching maneuver experiments of Harris’ hawks that birds minimize the distance flown at high angles of attack to dissipate kinetic energy before impact. The resulting drone flight trajectories, morphing sequence, and kinetic energy distribution resemble those measured in birds. Furthermore, experimental manipulation of the wings that would be difficult or unethical with animals reveals the morphing factors that are critical for optimal perching maneuver performance of birds and morphing-wing drones. Birds’ agile perching maneuvers allow large energy dissipation in short approach flights. Here, authors test an objective that birds are hypothesized to employ in perching maneuvers on an avian-inspired drone and find that it mimics the birds’ behavior, enabling exploration of key morphing actuations.

Urbanization is a process of environmental change which reduces and fragments the original habitat and creates new pressures, conditions, and resources for the species. The urban areas act as an ecological filter, which may exclude species, while others can colonize and thrive in cities, generating a process of biotic homogenization. As top predators, the changes in prey community composition could affect the diet of raptors. However, this effect has been understudied. In this study we compiled information about the frequency of prey consumed by Cooper's Hawk, Common Black Hawk, Roadside Hawk and Gray Hawk using two sources of information: (1) data extracted from photographs available on citizen science platforms and (2) a search of scientific literature. Using these data, we compared the diet composition, the proportion of prey consumed and the trophic niche breadth by four species of raptor in urban and non-urban areas. Additionally, we evaluated whether the variability in frequency of predation records by raptors was associated to the type of prey or their breeding season. Our results indicate that the raptors studied consumed at least 91 prey species in Mexico. Most records of predation by Common Black Hawk, Roadside Hawk, and Gray Hawk occurred in non-urban areas. On the contrary, most records of predation by Cooper's hawks occurred within urban areas. There was no statistical difference in the richness of prey consumed by Cooper's Hawk and Gray Hawk between urban and non-urban areas. In contrast, fewer prey types were consumed by Common Black Hawk and Roadside Hawk in urban areas than in non-urban areas. The proportion of prey types consumed in urban and non-urban areas was significantly different for Cooper's Hawk, Roadside Hawk and Gray Hawk. Conversely, the proportion of prey types consumed by Common Black Hawk's was similar in urban and non-urban areas. The four raptors studied increased the proportion of birds consumed in urban areas by between 2% and 36%, regardless of their preference for a specific type of prey. The trophic niche breadth of raptors was broader in urban areas than in non-urban areas, except for Cooper's Hawk, which had a narrow trophic niche breadth in urban areas than in non-urban areas. The temporal variation in the frequency of predation records was influenced by differential factors such as the breeding season, the type of prey consumed, and the utilization patterns of citizen science platforms. Our results demonstrate that the four raptors studied increased the proportion of bird consumption in urban areas. This shift in raptors' diets could be linked to the increased prevalence of diseases transmitted by feeding on infected birds in urban areas. This emphasizes the importance of conducting research to assess the prevalence and transmission rates of diseases that could threaten the conservation of birds and raptors in urban areas.

Urbanization causes the simplification of natural habitats, resulting in animal communities dominated by exotic species with few top predators. In recent years, however, many predators such as hawks, and in the US coyotes and cougars, have become increasingly common in urban environments. Hawks in the Accipiter genus, especially, are recovering from widespread population declines and are increasingly common in urbanizing landscapes. Our goal was to identify factors that determine the occupancy, colonization and persistence of Accipiter hawks in a major metropolitan area. Through a novel combination of citizen science and advanced remote sensing, we quantified how urban features facilitate the dynamics and long-term establishment of Accipiter hawks. Based on data from Project FeederWatch, we quantified 21 years (1996–2016) of changes in the spatio-temporal dynamics of Accipiter hawks in Chicago, IL, USA. Using a multi-season occupancy model, we estimated Cooper's ( Accipiter cooperii ) and sharp-shinned ( A. striatus ) hawk occupancy dynamics as a function of tree canopy cover, impervious surface cover and prey availability. In the late 1990s, hawks occupied 26% of sites around Chicago, but after two decades, their occupancy fluctuated close to 67% of sites and they colonized increasingly urbanized areas. Once established, hawks persisted in areas with high levels of impervious surfaces as long as those areas supported high abundances of prey birds. Urban areas represent increasingly habitable environments for recovering predators, and understanding the precise urban features that drive colonization and persistence is important for wildlife conservation in an urbanizing world.

When multiple species are vulnerable to a common set of predators, it is advantageous for individuals to recognize information about the environment provided by other species. Eastern gray squirrels (Sciurus carolinensis) and other small mammals have been shown to exploit heterospecific alarm calls as indicators of danger. However, many species-especially birds-emit non-alarm auditory cues such as contact calls when perceived predator threat is low, and such public information may serve as cues of safety to eavesdroppers. We tested the hypothesis that eavesdropping gray squirrels respond to \"bird chatter\" (contact calls emitted by multiple individuals when not under threat of predation) as a measure of safety. We compared vigilance behavior of free-ranging squirrels in the presence of playbacks of bird chatter vs non-masking ambient background noise lacking chatter after priming them with a playback recording of a red-tailed hawk (Buteo jamaicensis) call. Squirrels responded to the hawk call playbacks by significantly increasing the proportion of time they spent engaged in vigilance behaviors and the number of times they looked up during otherwise non-vigilance behaviors, indicating that they perceived elevated predation threat prior to the playbacks of chatter or ambient noise. Following the hawk playback, squirrels exposed to the chatter treatment engaged in significantly lower levels of vigilance behavior (i.e., standing, freezing, fleeing, looking up) and the decay in vigilance behaviors was more rapid than in squirrels exposed to the ambient noise treatment, suggesting squirrels use information contained in bird chatter as a cue of safety. These findings suggest that eastern gray squirrels eavesdrop on non-alarm auditory cues as indicators of safety and adjust their vigilance level in accordance with the vigilance level of other species that share the same predators.

Aerial predators adopt a variety of different hunting styles, with divergent flight morphologies typically adapted either to high-speed interception or manoeuvring through clutter, but how are their sensorimotor systems tuned in relation to habitat structure and prey behavior? Falcons intercept prey at high-speed using the same proportional navigation guidance law as homing missiles. This classical guidance law works well in the open, but performs sub-optimally against highly-manoeuvrable targets, and may not produce a feasible path through the cluttered environments frequented by hawks and other raptors. Here we identify the guidance law of n  = 5 Harris’ Hawks Parabuteo unicinctus chasing erratically manoeuvring artificial targets. Harris’ Hawks use a mixed guidance law, coupling low-gain proportional navigation with a low-gain proportional pursuit element. This guidance law promotes tail-chasing and is not thrown off by erratic manoeuvres, making it well suited to the hawks’ natural hunting style, involving close pursuit of agile prey through clutter. Hunting styles and flight morphologies of aerial predators are adapted to their habitat structure and prey behaviour. Here, the authors reconstruct flight trajectories of Harris’ Hawks Parabuteo unicinctus and find that these follow a mixed guidance law that is not thrown off by erratic manoeuvres of prey.

Personality differences can be found in a wide range of species across the animal kingdom, but why natural selection gave rise to such differences remains an open question. Frequency-dependent selection is a potent mechanism explaining variation; it does not explain, however, the other two key features associated with personalities, consistency and correlations. Using the hawk-dove game and a frequency-dependent foraging game as examples, we here show that this changes fundamentally whenever one takes into account the physiological architecture underlying behavior (e.g., metabolism). We find that the inclusion of physiology changes the evolutionary predictions concerning consistency and correlations: while selection gives rise to inconsistent individuals and stochastically fluctuating behavioral correlations in scenarios that neglect physiology, we find high levels of behavioral consistency and tight and stable trait correlations in scenarios that incorporate physiology. The coevolution of behavioral and physiological traits also gives rise to adaptive physiological differences that are systematically associated with behavioral differences. As well as providing a framework for understanding behavioral consistency and behavioral correlations, our work thus also provides an explanation for systematic physiological differences within populations, a phenomenon that appears to exist in a wide range of species but that, up to now, has been poorly understood.

Previous studies have shown that the threat level posed by a predator can vary with physical features. In this study, we tested whether the wing posture of a raptor could serve as a clue for bird threat assessment. We observed the behavioral response of Japanese tits Parus minor to taxidermy dummies Eurasian sparrowhawks Accipiter nisus with either spread wings and closed wings. The results showed that the response scores to sparrowhawks with spread wings were higher than those to sparrowhawks with closed wings. We suggested that Japanese tits can assess the predation risk associated with changes in wing posture of predators.

The charisma of top vertebrate predators is often used by conservationists as a lever for financial support, to raise environmental awareness and in planning protected areas : a strategy that has been criticized. Here we use information collected from five raptor species that differ widely in their diet and habitat associations to show that sites occupied by these predators are consistently associated with high biodiversity. The biodiversity at these sites is more extensive than it is at sites selected at random, or at sites occupied by species from lower down the trophic pyramid (insectivorous or herbivorous species, for example). Our results indicate that conservation focusing on top predators can be ecologically justified because it delivers broader biodiversity benefits.

Preserving biodiversity in urban ecosystems has become an urgent conservation priority, given the rapid upsurge in global urbanization. As woody plants play essential ecological roles and provide psychological benefits to human city dwellers, their preservation is of particular interest to conservation scientists. However, considering that extensive censuses of woody plants are resource-intensive, a key accomplishment is to find reliable conservation proxies that can be quickly used to locate biologically diverse areas. Here, we test the idea that sites occupied by apex predators can indicate high overall biodiversity, including high diversity of woody plants. To this end, we surveyed woody plant species within 500 m of Northern Goshawk ( Accipiter gentilis ) breeding sites in urban ecosystems of Japan and compared them with non-breeding control sites without goshawks. We found that goshawks successfully identified and signposted high levels of richness, abundance, and diversity of woody plants. Our findings show that sites occupied by top predatory species could be exploited as conservation proxies for high plant diversity. Due to their exigent ecological requirements, we would expect apex predators to be tied to high biodiversity levels in many other urban ecosystems worldwide.

1. Avian migrants often make substantial detours between their seasonal destinations. It is likely some species do this to make the most of predictable wind regimes along their respective flyways. We test this hypothesis by studying orientation behaviour of a long-distance soaring migrant in relation to prevailing winds along the East Atlantic Flyway. 2. We tracked 62 migratory journeys of 12 adult European Honey Buzzards Pernis apivorus with GPS loggers. Hourly fixes were annotated with local wind vectors from a global atmospheric model to determine orientation behaviours with respect to the buzzards' seasonal goal destinations. This enabled us to determine hot spots where buzzards overdrifted and overcompensated for side winds. We then determined whether winds along the buzzards' detours differed from winds prevailing elsewhere in the flyway. 3. Honey Buzzards cross western Africa using different routes in autumn and spring. In autumn, they overcompensated for westward winds to circumvent the Atlas Mountains on the eastern side and then overdrifted with south-westward winds while crossing the Sahara. In spring, however, they frequently overcompensated for eastward winds to initiate a westward detour at the start of their journey. They later overdrifted with side winds north-westward over the Sahel and north-eastward over the Sahara, avoiding adverse winds over the central Sahara. 4. We conclude that Honey Buzzards make seasonal detours to utilize more supportive winds further en route and thereby expend less energy while crossing the desert. Lifelong tracking studies will be helpful to elucidate how honey buzzards and other migrants learn complex routes to exploit atmospheric circulation patterns from local to synoptic scales.