DAILY AND SEASONAL DYNAMICS OF THE VOCALIZATION OF THE EAGLE OWL (BUBO BUBO, STRIGIFORMES, STRIGIDAE) IN THE CENTRAL VOLGA REGION

摘要

Both daily and seasonal year-round vocalizations of the eagle-owl were recorded in the central Volga River region, Russia with the use of digital dictophones. Two best-expressed peaks of long-term activity were revealed during a year: one since early February until early April and the other since early August until early October. During the incubation period, vocalizations of each bird surveyed lasted on the average 79 min per day. The second annual peak of vocalization was restricted to brood disintegration and the formation of new couples. During that period, calls averaged 63 min per day. The acoustic activity during the nestling period (April to May) when birds were leaving the nests was less strongly expressed: on the average each eagle-owl vocalized 32 min per day. Both in June and July, eagle-owls called little and their general vocalizations averaged 9 min per day. From October 29, 2015 to February 4, 2016, the eagle-owl remained silent in nesting habitats. From spring to fall, eagle-owls resumed calling one hour before sunset, as a rule. In February, vespers started later than in other seasons, on the average 30 min before sunset. Completion of morning vocalizations usually took place 1.5 h before sunrise. Statistically significant differences in the duration of vespers and morning vocalizations were obtained with the use of Mann Whitney U test (Z = -3.38, p 0.05).