Human Disturbance Affects Parental Care of Marsh Harriers and Nutritional Status of Nestlings

Most studies of the effects of human disturbance on reproduction in birds of prey have not quantified the subtle and potentially important aspects of such interactions. Thus, we studied the effects of human disturbance on parental care by marsh harriers (Circus aeruginosus) in spring 1991 at Dos Reinos Lake, Ebro Valley, Spain. Specifically, we assessed changes in reproductive activities and nutritional condition of nestlings due to low-level human disturbance during incubation and nestling phases. The number of food items delivered and the time spent by males and females in the nesting area and on the nest decreased during disturbed periods, especially during incubation (P < 0.001), whereas behaviors related to stress (alarm calls, chases against other intruding birds, and percentage flying time) increased (P < 0.001)