Boldness as an Individual Trait of Behaviour in a Natural Population of Birds

Individual resoluteness during the resumption of feeding of nestlings was examined in tests involving the presentation of an unfamiliar object near the nests of the pied flycatcher ( Ficedula hypoleuca ) in a natural environment. Over the course of five breeding seasons, 229 individuals were tested, 41 of which were tested 2 to 4 times. Repeat testing of the same birds was conducted at different nests with intervals ranging from 3 to 1103 days (Med = 367). We took into account the number and age of nestlings, nesting periods, the sex and age of the individual and its partner, the presence of molting, the intensity of nestling feeding, the behavior of the partner, as well as the presence of simultaneous bigamy in the male. We revealed a significant repeatability of test results over substantial time intervals ( R = 0.21), indicating the individual’s stability over time in response (boldness) to changing conditions in the natural environment.