ИСТИНА

Most of knowledge about bird vocalization ontogenesis comes from studies of song development in passerine birds (Passeriformes), but development of vocalization in other taxa is poorly known. Some Anseriformes and Galliformes demonstrate gradual changes of call-frequency variables values during development, while some Gruiformes, Coraciiformes and Columbiformes show jump-like changes of them. We analyzed early vocal development in two diurnal bird of prey species (Falconifornes): Saker Falcon (Falco cherrug) and Northern Goshawk (Accipiter gentilis). All diurnal birds of prey have semi-altricial chicks that hatch sighted and stay in nests until fledging. We recorded calls from 7 Saker Falcon and 4 Northern Goshawk chicks between hatching and fledging age stages in Vitasfera Rare Bird Species Breeding center. We collected 15 signals per chick every 3 days (1160 signals in total). We found two main call types - begging for food and discomfort call - in chick vocal repertoire for both species. Chicks used calls of both types since hatching. Call-frequency and call duration variables were observed only for begging for food call. Fundamental frequency gradually decreased between calls of hatchlings and fledglings in both species, but it was higher than that in calls of adults. Call duration decreased in saker falcon, but merely fluctuated in northern goshawk with age. According to fundamental frequency changes we divided period between hatching and fledging in two: early and late ones. Thus, we confirm gradual vocal development in diurnal birds of prey