Population trend, breeding performance and diet of Saker Falcons <i>(Falco cherrug)</i> in Hungary between 1980 and 2024

Abstract The Saker Falcon (Falco cherrug) is a globally threatened bird species, and Hungary hosts the second-largest population in Europe. The Hungarian population most likely reached its historical minimum by the 1970s, with an estimated number of 15–30 breeding pairs. Intensive monitoring and conservation efforts began in 1980 through the cooperation of MME BirdLife Hungary and the national park directorates. In this paper, we present the long-term natural history of the Hungarian Saker Falcon population from 1980 to 2024. Throughout the study period, both range expansion and breeding population size exhibited an increasing trend. The number of known territorial pairs grew at an average annual rate of approximately 8%. The population reached its historical maximum in 2024, when 200 territorial pairs were recorded, of which 177 successfully bred, producing 530 fledglings. A total of 4,429 breeding attempts were monitored in Hungary over 45 years, of which 3,467 were successful, yielding 10,319 nestlings. The breeding performance parameters of the population showed a generally stable trend with slight fluctuations throughout the study period. The annual mean (±SD) success rate was 0.76 (±0.14), and the mean brood size was 2.94 (±0.29), resulting in an overall productivity of 2.26 (±0.49). Following the socio-economic changes in Hungary in the 1990s, the breeding population of Saker Falcons shifted its range from the mountains to the lowlands. This shift was driven by decreased persecution of raptors, habitat changes and the subsequent decline in the availability of key prey species in the foothills. Between 1986 and 2015, 24,882 identifiable prey items of Saker Falcons were recorded, belonging to 164 different taxa. Diet analysis revealed that four species played a particularly significant role in the diet of Saker Falcons in Hungary: Feral Pigeon (Columba livia f. domestica) , European Ground Squirrel (Spermophilus citellus) , Common Starling (Sturnus vulgaris) , and Common Vole (Microtus arvalis) . Although Columbiformes remained the most common prey group, their abundance did not show a significant trend. In contrast, the proportion of Passeriformes increased significantly. A more pronounced change was observed among mammals in the diet. The previously common European Ground Squirrel declined dramatically, while the proportion of other Rodentia and Lagomorpha species increased significantly. The growth of the Hungarian Saker Falcon population halted after 2010. However, a slight increase has been observed in recent years (2018–2024), raising the hope that a gradual recovery may still be possible in the coming decades.