Saker falcon populations suffered severe declines, especially in the second half of the 20^th century. During the period between 2004 and 2018, the species became extinct in Bulgaria as a breeding species. After that, a reintroduction program was implemented with birds originating from central Europe. We studied the main behavioral characteristics of both wild sakers from the local population of the species in SE-Bulgaria and these of the reintroduced birds which started breeding in the same region in a wild in 2018. We collected numerous observations on the territorial, hunting, and breeding (parental) behavior of that species. Territorial attacks against 16 bird species were recorded with prevailing numbers against kestrel (Falco tinnunculus) and imperial eagle (Aquila heliaca). The main hunting strategies of the species included attacks against sousliks (Spermophilus citellus) in their numerous colonies in the study area. Various species of birds were also captured and brought in the nest. Adults were feeding the nestlings in 31.5–55.3 min intervals depending on their age. In the morning hours (7 am – 12 pm) the duration of the feeding of the nestlings is lower – 11.35±3,5 min on average, compared to the afternoon (12 pm – 5 pm) – 18.81±6,81 min. After the disappearance of a female in 2021, the male alone fed and cared for three nestlings during a period of 19 days. The male stopped feeding the nestlings after finding another female and consequently all the nestlings were found dead.

breeding season, ethology, falcons, feeding, hunting effort, nestlings, territoriality, reintroduction.