Notes on the Short-toed Eagle breeding in the North of Zhytomyr Region

Up to now Short-toed Eagle is a little-studied species in Ukraine despite the presence of a quite big population. Its biology was studied in the Polesskij Nature Reserve during the 1988-1995 years. The average breeding success was about 0.67 juv/pair. One pair and 9 nesting cases were observed. There was only one single egg in a nest in all cases.

In the secure conditions of the Polesskij Nature Reserve the same nests were used by Short-toed Eagles 3 years on end. Usually they change their nests every year, though they are quite constant in the choice of a nesting place. All nests in a region of the P. N. Reserve were located on pines on the hexenbesen – dense pile of branches in the form of a bowl; most of the nests were situated on the main trunk.

In Ukraine the most probable time when young Short-toed Eagles leave their nests is the period between August 10^th and September 10^th. Though the approach of a man to the nest can provoke earlier the taking wings of the young, but in the P. N. Reserve even close photographing of a young Short-toed Eagle that already was practically the same in size as the adult didn’t make it leave the nest.

Comparative breeding phenology is represented in the picture, according to observations of 6 breeding cases: egg laying – 28.04 > hatch – 13.06 > leaving of the nest (after 76 days) 28.08. Some authors specially mark one more period – the provision of the young near a nest.

In the P. N. Reserve 33 food remains were collected: 27 (81.8%) – reptiles, 3 (9.1%) – amphibious, 2 (6.1%) – mammals, 1 (3.0%) – bird (jay). Among reptiles Vipera berus is the most usual – 16 (48.5%), Natrix natrix – 4 (12.1%), Coronella austriaca – 1 (3.0%), lizards – 6 (18.2%).

According to author’s data the minimal number of Short-toed Eagle in the Zhytomyr Region is about 15 nesting pairs. Approximate density of the Short-toed Eagle population in the region of the Reserve is 1-2 nesting pairs per 1 thousand km². Discovery of Short-toed Eagle nests in big swamped forestlands like the Polesskij Nature Reserve is a difficult problem because of the small size and good masking of the nests and because of the impossibility to determine the direction of flights of adult Eagles with a prey.