Seasonal variations in niche partitioning between two sympatric sandgrouse

Ecologists have long sought to understand how species with similar ecological niches coexist, especially in sympatric environments. Traditional studies using low-resolution presence and environmental data have provided insights into these processes but often focus on a single season (mainly breeding) and are limited in capturing spatiotemporal environmental variation. Recent developments in satellite data and high-resolution biologging now enable researchers to better understand species coexistence and distribution in dynamic ecosystems. Sandgrouse (Pteroclidae) are ideal for studying niche dynamics and coexistence due to their narrow environmental requirements year-round. Here, we investigated habitat suitability and niche overlap between pin-tailed (Pterocles alchata) and black-bellied sandgrouse (Pterocles orientalis) in a Special Protection Area in southwestern Iberia, where both species occur in sympatry year-round. From 2021 to 2023, we tracked 35 P. alchata and 26 P. orientalis using high-resolution GPS devices, matching locations with 10-metre resolution environmental and anthropogenic variables from Sentinel-1 and -2 satellite imagery collected every six days. We applied random forest models across seasons to identify variables influencing each species' niche and to predict habitat suitability. Ecological niches were compared in environmental and geographic space, alongside patterns of space use, and niche overlap was quantified across species and seasons using Horn's R and Schoener's D indices. Our models predicted habitat suitability at a very high 10-metre resolution. In environmental space, we found moderate to high niche overlap across species and seasons, with habitat-related variables shaping both species’ niches across seasons. Between species, niche overlap was higher during the breeding season, while P. alchata showed greater seasonal niche segregation than P. orientalis. Despite shared ecological requirements, analyses in geographic space showed distinct patterns between suitability projections and actual space use, indicating that spatial segregation is likely promoted not only by seasonal variations in suitability but also by other ecological processes, facilitating sandgrouse coexistence.