Are population changes of endangered little bustards associated with releases of red-legged partridges for hunting? A large-scale study from central Spain

The release of farm-reared game birds for hunting is an increasingly common game management practice. However, releasing could have negative effects on sympatric wild species, for example, through parasite transmission. Here, we document the spatial-temporal patterns and intensity of red-legged partridge releases in the province of Ciudad Real, Spain, over a 15-year period (2002–2016), relating them to local changes in the abundance of little bustards estimated from two surveys carried out in 2005 and 2016. Within the province, > 600,000 red-legged partridges were released annually over at least 20% of the area. Releasing intensity varied between estates and fluctuated over the 15-year study period, probably because of an economic crisis during 2008–2014. Overall, numbers of little bustards dropped by 46% between surveys, the decrease being more marked in the west of the province. Contrary to expectation, the only hunting estates where little bustards did not decrease were those with higher release intensity. This may be a consequence of management measures or other factors that benefit little bustards and are more prevalent on those estates than elsewhere, such as game crop provision, predator control or habitat quality.Xabier Cabodevilla was supported by a PhD grant and an internship grant, financed by the Basque Country government (grants no. PRE_2018_2_0273 and EP_2019_1_0070). This study contributes to the project AGROPERDIZ (SBPLY/17/180501/000245) funded by the “Fondo Europeo de Desarrollo Regional” (Feder) and Junta de Communidades de Castilla-La Mancha.Peer reviewe