Foraging and parental behaviour of a saker falcon pair raising five fledglings

The population restoration of regionally extinct raptors is often challenging, especially in the initial establishment of the population. The endangered saker falcon (Falco cherrug) became extinct as a breeding species in Bulgaria since 1997 but has recently been reintroduced. The first breeding occurred in 2017, and currently six breeding territories are occupied. We investigated the parental behaviour of a breeding pair that successfully raised five fledglings in 2025. We aimed to quantify parental provisioning by sex, describe prey handling and food-transfer behaviour, and estimate prey demand. A total of 56 prey deliveries were recorded during 90.7 h of observation. European ground squirrels (Spermophilus citellus) were the primary prey, accounting for 85% of provisioning by the male and 92% by the female parent. In 46 food-provisioning events with ascertained hunting individual, the male captured the prey in 72% of the cases (female in 28%). Male-to-female food transfers were recorded in 15 cases, of which 8 were in the air and 7 in the nest. All but one prey items were brought to the nest decapitated. The female fed the chicks in 85% of cases (male in 15%). The average feeding duration was 14 ± 3.84 min. Based on the observed provisioning rates, we estimated that the pair and their offspring may have preyed on approximately 600 sousliks during the entire breeding season. Future research needs to focus on whether territorial pairs in Bulgaria are resident throughout the winter, on studying hunting behaviour outside the breeding season, and on assessing the number of sousliks gained by, or lost to, kleptoparasitism.