Breeding biology and diet of Tawny eagles (Aquila rapax) in desert National Park, Rajasthan, India

Abstract

The Tawny Eagle (Aquila rapax), is raptor species, found across the Indian subcontinent, widely spread and poorly studied. There is very limited quantitative information present on the nest-site selection, breeding behaviour and diet selection of Tawny Eagles. This study investigates the factors influencing habitat selection, breeding ecology and diet composition of the population of Tawny Eagles in the Thar desert landscape of Rajasthan, India, during the 2025-2026 breeding season. This study aimed to provide a baseline understanding of the species ecology by examining nest-site selection, spatial distribution of nests, parental behaviours, provisioning behaviours and seasonal changes in prey compositions. Nest search was conducted across approximately, 2000 km2, with approximately 4000 km of nest search effort with active nest tree characteristics mapped, and distance between the nest and the protected grasslands calculated. A total of ten nests were found across the study area, with all nest occurring within, or in close proximity to the protected grasslands in Desert National Park. Nine out of ten nests were either inside enclosures or located immediately adjacent to them, with an average distance of 1.56 km from enclosure boundaries. Nest trees were predominantly Prosopis cineraria, with nesting trees averaging over 7.5 m in height and providing large crown structures suitable for nest placement, with all nests being placed at the top of the tree. As all the nests were recorded in only a small part of the study area, a rapid population survey was conducted across the study area to determine the spatial distribution of the species across the study area. Raptor surveys covering 734.78 km across 63 grids recorded 14 Tawny Eagle sightings, confined largely to areas where nests had been located. Breeding behaviour was studied using focal observations and CCTV monitoring across active nests, generating approximately 900 hours of behavioural data. Breeding was found to occur in the winter months, with most eggs being laid in December and January, hatching in the months of January and February, with fledging occurring by the end of March through April. Results showed differences in parental roles, with females primarily responsible for nest attendance and chick care, while males acted as the primary providers of prey. Female nest attendance decreased as chicks matured, while chick vigilance increased with age. Provisioning behaviour demonstrated seasonal variation, with Spiny-tailed Lizards (Saara hardwickii) becoming the dominant prey item during warmer months. Diet composition was assessed using pellet analysis, CCTV observations, and drone surveys, resulting in 224 prey records from nine nests. Tawny Eagles showed dietary flexibility, with mammals (41.9%) and reptiles (40.1%) comprising the majority of prey items. Diet composition changed significantly across months and nesting stages, with a shift from mammalian prey during colder months towards increased reptilian prey as temperatures rose and Spiny-tailed Lizards became more available. Overall, this study highlights the importance of protected grassland habitats within Desert National Park for supporting Tawny Eagle populations by providing suitable nesting structures, reduced disturbance, and productive foraging habitats. The findings provide the first detailed quantitative assessment of habitat selection, breeding behaviour, and diet composition of Tawny Eagles from the Indian population and establish a foundation for future long-term studies on population status, reproductive success, and conservation requirements of this species.