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Here, we analyse the energetics, performance and optimization of flight in a moving atmosphere. We begin by deriving a succinct expression describing all of the mechanical energy flows associated with gliding, dynamic soaring and thermal soaring, which we use to explore the optimization of gliding in an arbitrary wind. We use this optimization to revisit the classical theory of the glide polar, which we expand upon in two significant ways. First, we compare the predictions of the glide polar for different species under the various published models. Second, we derive a glide optimization chart that maps every combination of headwind and updraft speed to the unique combination of airspeed and inertial sink rate at which the aerodynamic cost of transport is expected to be minimized. With these theoretical tools in hand, we test their predictions using empirical data collected from a captive steppe eagle (Aquila nipalensis) carrying an inertial measurement unit, global positioning system, barometer and pitot tube. We show that the bird adjusts airspeed in relation to headwind speed as expected if it were seeking to minimize its aerodynamic cost of transport, but find only weak evidence to suggest that it adjusts airspeed similarly in response to updrafts during straight and interthermal glides. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.

Raptors face global threats like electrocution, collisions, and habitat fragmentation. Many species remain understudied, and their distribution patterns are unknown. Understanding their current and future distribution is crucial for conservation. Protecting these top predators requires knowledge of their spatial distribution and environmental influences. This study addresses knowledge gaps in raptor habitats and distributions in Kenya, considering current and future climate changes. Using species distribution models and occurrence data from the Global Biodiversity Information Facility, we evaluated suitable habitats for four endangered Kenyan raptor species: Martial eagle, Secretarybird, Bateleur, and Steppe Eagle. We assessed the impact of climatic predictors on their distribution, considering two climate change scenarios for 2020–2040. Our findings reveal that raptor distribution in Kenya is predominantly concentrated in the southwestern region, extending into the central region of the country. The most significant predictors of raptor species distribution varied for each species, with Steppe eagle and Secretarybird being highly influenced by precipitation during the warmest quarter, Martial eagle being influenced by mean temperature during the driest quarter, and Bateleur being primarily influenced by precipitation during the coldest quarter. When projecting our model into the climate change scenarios for 2020–2040, all species except the Bateleur exhibited a negative range shift. The results of our study suggest that climate change may have adverse impacts on the raptor species examined. In light of these findings, we recommend implementing targeted monitoring and conducting surveys in accordance with our current model predictions. Specifically, our focus should be on monitoring areas that exhibit the highest climate suitability, as these areas are likely to undergo significant shifts in the near future. By conducting regular monitoring and engaging in further research, we can enhance our understanding of these raptor species and gather valuable data to improve the accuracy and reliability of our model predictions. Spatial patterns and future projections of raptors in Kenya in the face of climate change.

Saudi Arabia is the fastest growing electricity consumer in the Middle East, with a rapidly expanding network of powerlines. Bird mortality through electrocution and collision has been recorded in the country, but so far there is little information as to how much the electricity infrastructure affects globally threatened raptor populations that migrate to Saudi Arabia. In 2019, the world’s largest wintering congregation of Steppe Eagles Aquila nipalensis was discovered near a rubbish dump in central Saudi Arabia. We evaluated whether powerlines in the vicinity of this, and another congregation site, caused mortality of large birds. In November 2019, we surveyed powerlines within 6 km of two focal rubbish dumps at Al Qunfudhah (12.4 km) and Ushaiqer (2 km). We found 52 carcasses of five species, of which 85% were Steppe Eagles. Based on the age of these carcasses, we coarsely extrapolate that 14.4 km of powerlines near these two congregation sites may kill 94–240 Steppe Eagles per winter, representing up to 0.3% of their global population. We call for the urgent safeguarding of powerlines that cause mortality near known Steppe Eagle congregation sites, and the adoption and implementation of regulations that ensure that future infrastructure is constructed with designs that are safe for birds.

The steppe eagle (Aquila nipalensis) is an endangered migratory raptor species that migrates in winter to Pakistan and neighbouring countries. In Pakistan, the species migrate at the end of autumn and utilise different habitats across the country. Very little information is available about the species’ population status, distribution, and factors affecting its distribution in Pakistan. In the present study, we predicted the distribution of steppe eagles in Pakistan associated with different environmental variables. We used 149 presence points of the species from an online source (GBIF), published literature, and wildlife photographers. The MaxEnt analysis showed that highly suitable habitats were mostly present in Azad Jammu and Kashmir (AJK), federally administered areas and surrounding areas, southern areas of Sindh Province, and some parts of Khyber Pakhtunkhwa (KP) Province. In addition, some patches were also predicted by MaxEnt in Balochistan Province. Human population density (27.0%), chicken density (16.6%), temperature seasonality (11.1%), and rivers (10.3%) were identified as the main environmental factors that affect the habitat distribution of steppe eagle in Pakistan. Only a small percentage (2.62%) of the total Pakistan area was estimated to be a highly suitable area for steppe eagles, while 20.58% and 7.46% were identified as the least and moderately suitable areas, respectively. Conservation of identified habitats and mitigation of anthropogenic impacts to conserve this endangered eagle species are recommended for immediate and long-term conservation across Pakistan.

Background Diet analysis is essential to understanding the functional role of large bird species in food webs. Morphological analysis of regurgitated bird pellet contents is time intensive and may underestimate biodiversity. DNA metabarcoding has the ability to circumvent these issues, but has yet to be done. Methods We present a pilot study using DNA metabarcoding of MT-RNR1 and MT-CO1 markers to determine the species of origin and prey of 45 pellets collected in Qinghai and Gansu Provinces, China. Results We detected four raptor species [Eurasian Eagle Owl (Bubo bubo), Saker Falcon (Falco cherrug), Steppe Eagle (Aquila nipalensis), and Upland Buzzard (Buteo hemilasius)] and 11 unique prey species across 10 families and 4 classes. Mammals were the greatest detected prey class with Plateau Pika (Ochotona curzoniae) being the most frequent. Observed Shannon’s and Simpson’s diversity for Upland Buzzard were 1.089 and 0.479, respectively, while expected values were 1.312 ± 0.266 and 0.485 ± 0.086. For Eurasian Eagle Owl, observed values were 1.202 and 0.565, while expected values were 1.502 ± 0.340 and 0.580 ± 0.114. Interspecific dietary niche partitioning between the two species was not detected. Conclusions Our results demonstrate successful use of DNA metabarcoding for understanding diet via a novel noninvasive sample type to identify common and uncommon species. More work is needed to understand how raptor diets vary locally, and the mechanisms that enable exploitation of similar dietary resources. This approach has wide ranging applicability to other birds of prey, and demonstrates the power of using DNA metabarcoding to study species noninvasively.

ABSTRACT Land use type changes the carrying capacity of habitats to support species diversity and maintain viable population. Avian studies provide substantial information about these changes as birds are predictor of ecological disturbances. The current research explored the avian diversity, richness, abundance and their feeding habit in selected habitats of Khyber Pakhtunkhwa (KP) and Gilgit Baltistan (GB). Data were collected from May 2017 to October 2017 using point count technique. Thirty points were selected from each habitat. A total of 175 species and 24,933 individuals belonging to 16 orders and 55 families were recorded. Human settlements had the highest species richness (106) while Dry Temperate habitat had the highest value of species diversity (H'=3.71). The most abundant species were Common Myna Acridotheres tristis (RA=8.599), Carrion Crow Corvus corone (7.486), Large-billed Crow Corvus macrorhynchos (6.240). Two threatened bird species Steppe Eagle Aquila nipalensis and Western Tragopan Tragopan melanocephalus were observed. Habitat suitability index (HSI) of former species was maximum in rangelands (0.82) even though it was also observed in six habitats. Furthermore, Western Tragopan was found only in moist temperate habitat with HSI 0.70. The current study revealed that suitable habitat of these species is shrinking mainly due to habitat loss, its fragmentation and hunting pressure. Species prefer habitat with specific characteristics and this paper provides recommendations for the conservation and management of Steppe Eagle and Western Tragopan. Primary and secondary data based further studies are needed to manage the population of threatened species.

Mitochondrial genome sequences are valuable resources for systematics and conservation biology studies. In this paper, we present the complete mitogenome of Aquila nipalensis which was 18,450 bp in length. The gene content and arrangement were typical for avian mtDNA. The overall A + T content of was 54.1%, and the AT skew was calculated as 0.12 for the complete mitogenome of A. nipalensis. The maximum-likelihood (ML) tree based on the concatenated 12 protein-coding genes (PCGs) revealed the basal phylogenetic position of A. nipalensis in Aquila.

We trapped 16 Steppe Eagles (Aquila nipalensis) on migration and on their wintering grounds and fitted them with satellite transmitters, 15 of them in Saudi Arabia and one in South Africa. Seven of the 14 Steppe Eagles trapped in Arabia in autumn did not migrate to Africa but spent the winter in the Arabian Peninsula. One adult migrated to southern Africa. The other six wintered in northeastern Africa, in some cases north of Bab-el-Mandeb, the straits at the southeastern end of the Red Sea, which they had crossed to reach the African continent. On their spring migration all eagles wintering in Africa migrated via the Suez, Egypt-Eilat, Israel, area at the northern tip of the Red Sea. This loop migration around the Red Sea is probably caused by east winds that blow from October until April, making the return migration difficult via Bab-el-Mandeb. This finding should help to explain the difference in eagle numbers between spring and autumn at such migration bottlenecks as Eilat, Suez, and Bab-el-Mandeb. Unlike eagles coming from Sudan and Ethiopia, eagles wintering in southern Africa must make a considerable detour of over 1200 km to complete this loop. The increase in Steppe Eagles overwintering in Arabia has probably contributed to the decline in the number of birds passing through Eilat in spring during recent years. Rutas Migratorias de Aquila nipalensis entre Asia y Africa: Un Estudio por Medio de Telemetria SatelitalOriginal Abstract: Atrapamos 16 aguilas (Aquila nipalensis), incluyendo aves migratorias e invernantes (15 en Arabia Saudita y una en Sud Africa) y les colocamos transmisores satelitales. Siete de las 14 aguilas atrapadas en Arabia durante el otono no migraron hacia Africa, sino que invernaron en la Peninsula Arabica. Aparte de un adulto que migro hacia el sur de Africa, las restantes seis invernaron en Africa oriental, en algunos casos al norte de los estrechos al extremo sureste del Mar Rojo (Bab-el-Mandeb) los cuales cruzaron para alcanzar el continente africano. Durante la migracion primaveral, todas las aguilas que invernaron en Africa migraron via Suez y via el area de Eilat, alrededor del extremo norte del Mar Rojo. La migracion alrededor de este cuerpo de agua siguiendo una ruta diferente a la invernal, es probablemente causada por el viento que provenie del este entre octubre y abril, dificultando la migracion de retorno via Bab-el-Mandeb en febrero y marzo. Este descubrimiento debe ayudar a explicar la diferencia en los numeros entre primavera y otono en sitios como Eilat, Suez y Bab-el-Mandeb, que actuan como cuellos de botella. La migracion siguiendo dos rutas diferentes significa un desvio considerable de 1200 km para aquellas aguilas que invernan en el sur de Africa, pero no para las que vienen desde Sudan y Etiopia. El incremento de aves que inviernan en Arabia probablemente ha contribuido durante los ultimos anos a la disminucion en los numeros de aves que pasan a traves de Eilat en primavera.

Bateleurs (Terathopius ecaudatus), Steppe Eagles (Aquila nipalensis), and Tawny Eagles (Aquila rapax) were observed consuming termites during a termite emergence on 30 December 2012 in Mkomazi National Park and on 20 May 2013 in Tarangire National Park, Tanzania. This behavior is well known in Steppe and Tawny eagles, but these are the first records of Bateleurs using termites as a food source.

We examined phenological change in the spring migratory passage of the predatory steppe eagle Aquila nipalensis from 1977 to 2008. Data were collected at Eilat, Israel, a globally important site for migrating raptors. Changes in the observation dates of spring passage migration were examined using correlation and regression analyses to assess changes over time as well as potential relationships with temperature and with the Indian Ocean Dipole, an index of climate in the wintering area. Over the study period, the number of recorded steppe eagles decreased significantly, as did the proportion of juveniles. Despite the population decrease there was a rapid advance in first spring passage date. Although changes in passage dates were related to environmental conditions in wintering and en-route areas, we suggest that one possible additional reason for such a rapid advance is due to increasing competition between individuals for breeding territories due to dwindling habitats. In addition, changes to some aspects of the passage distribution may be a consequence of a changing age structure.