Nest site use and breeding ecology of white-tailed stonechat (Saxicola leucurus) in Pakistan.

The white-tailed stonechat (Saxicola leucurus) is a near-threatened, habitat-sensitive grassland passerine largely restricted to South Asia, where its populations are declining due to habitat degradation, agricultural encroachment, and climate change. We studied the species' breeding biology and nest-site use during the 2020 breeding seasons across two farmland regions in northwestern Pakistan: Mardan and Bajaur. A total of 53 (44 active) nests were monitored for clutch size, hatching and fledging success, and nest architecture. Clutch size and number of fledglings were significantly greater in nests that were in natural depression sites than those in other sites. We detected a trade-off between nest construction and investment in reproduction, with smaller clutches found for nests with an external diameter greater than 6 cm. Although nest site use and construction differed between the two regions, with nests in Bajaur generally being smaller in outer and inner diameter and placed lower to the ground compared to those in Mardan, overall breeding success was not significantly different. Our results illustrate the significance of microhabitat elements on reproductive success, portraying how specific nest-site attributes may act as cues to habitat quality. These findings highlight the importance of conserving S. leucurus and maintaining resilient grassland bird communities amid increasing agricultural transformation.