Орлан-белохвост в Самарской области, Россия

Abstract

Data on modern status of the White Tailed Eagle (Haliaeetus albicilla) population in the Samara district were collected in 1995-2007. Following satellite images Landsat ETM+ the total length of water reservoir and the Volga river banks in Samara district is 1018.1 km, the total length of forested banks 817.4 km (80.29%). Authors had surveyed 817 km of banks, 515.3 km of which were forested, to the end of 2007. Now 85 breeding territories of the White Tailed Eagle are known in the Samara district, 82 from which locates in the Volga river valley and water reservoirs of the Volga river (fig. 1). Nests were found in 42 breeding territories (49.4%). The total number of found nests was 57 including old nests. Nests was not found in 12 territories (14.1%), however broods were registered, and pairs of birds (mainly birds uttering mating-calls in spring) were observed in 21 territories (24.7%), and single birds with alarm behavior during breeding season in 10 territories (11.8%). At all we registered 52 breeding events, and breeding were noted during several years in the territory of the fish farm Suskan and Samara Luka. The average distance between nests and centers of neighbor breeding territories is 4.02±2.39 km (n=80; range 1-13 km, Ех=2,55) (Table 1).Usually a pair of eagles build their own nests at the distance 3-5 km from another (fig. 2). The density of eagles in the Volga river valley including data of counts in islands is 1 pair/10 km of banks or 1.59 pairs/10 km of forested part of banks. A total of 110-140 pairs of the White Tailed Eagle are estimated to breed in the Samara district. The number of White-Tailed Eagles in the Samara district increased in 1.5 times for last 5 years. We observed 169 adults during counts in breeding season (157 birds in breeding territories) and 67 subadults (without juveniles). The number of subadults was 28.39% of the total number of registered birds, that actually is the third part of population. The main region of winter concentration of eagles is the territory 400 км2 in area in vicinity of Zhigulevsk. We registered from 30 to 110 birds in different years. A half of registered pairs of eagles nests at the distance of 100 m from the water, 34.9% at the distance of 100-500 m from the water and 11.6% 500 -1000 m from the water (fig. 3). Hardly more than a half of breeding territories of eagles was found on slopes of water reservoirs (52%) and hardly less than a half (46%) in flood-lands (fig. 4). Now 59% of known nests in the district (n=57) located on poplars and 35% on pines (fig. 5). The most part of eagle nests located in the forks of trunks in the upper part of the trees (72%); on the tops and in the forks of large 14% of nests for each (fig. 6), and all nests with such locations were built on pines. The average brood size is 1.69±0.62 chicks (n=26; range 1 3). Comparing with data of 1930-40-s the number of eagles in the Samara district has increased in 4 times. Now the main threats for eagles are poaching and lead poisoning. A half of White-Tailed Eagle population in the Samara district inhabits IBAs, however a half of IBAs don't have any legislative protection. ; Data on modern status of the White Tailed Eagle (Haliaeetus albicilla) population in the Samara district were collected in 1995-2007. Following satellite images Landsat ETM+ the total length of water reservoir and the Volga river banks in Samara district is 1018.1 km, the total length of forested banks 817.4 km (80.29%). Authors had surveyed 817 km of banks, 515.3 km of which were forested, to the end of 2007. Now 85 breeding territories of the White Tailed Eagle are known in the Samara district, 82 from which locates in the Volga river valley and water reservoirs of the Volga river (fig. 1). Nests were found in 42 breeding territories (49.4%). The total number of found nests was 57 including old nests. Nests was not found in 12 territories (14.1%), however broods were registered, and pairs of birds (mainly birds uttering mating-calls in spring) were observed in 21 territories (24.7%), and single birds with alarm behavior during breeding season in 10 territories (11.8%). At all we registered 52 breeding events, and breeding were noted during several years in the territory of the fish farm Suskan and Samara Luka. The average distance between nests and centers of neighbor breeding territories is 4.02±2.39 km (n=80; range 1-13 km, Ех=2,55) (Table 1).Usually a pair of eagles build their own nests at the distance 3-5 km from another (fig. 2). The density of eagles in the Volga river valley including data of counts in islands is 1 pair/10 km of banks or 1.59 pairs/10 km of forested part of banks. A total of 110-140 pairs of the White Tailed Eagle are estimated to breed in the Samara district. The number of White-Tailed Eagles in the Samara district increased in 1.5 times for last 5 years. We observed 169 adults during counts in breeding season (157 birds in breeding territories) and 67 subadults (without juveniles). The number of subadults was 28.39% of the total number of registered birds, that actually is the third part of population. The main region of winter concentration of eagles is the territory 400 км2 in area in vicinity of Zhigulevsk. We registered from 30 to 110 birds in different years. A half of registered pairs of eagles nests at the distance of 100 m from the water, 34.9% at the distance of 100-500 m from the water and 11.6% 500 -1000 m from the water (fig. 3). Hardly more than a half of breeding territories of eagles was found on slopes of water reservoirs (52%) and hardly less than a half (46%) in flood-lands (fig. 4). Now 59% of known nests in the district (n=57) located on poplars and 35% on pines (fig. 5). The most part of eagle nests located in the forks of trunks in the upper part of the trees (72%); on the tops and in the forks of large 14% of nests for each (fig. 6), and all nests with such locations were built on pines. The average brood size is 1.69±0.62 chicks (n=26; range 1 3). Comparing with data of 1930-40-s the number of eagles in the Samara district has increased in 4 times. Now the main threats for eagles are poaching and lead poisoning. A half of White-Tailed Eagle population in the Samara district inhabits IBAs, however a half of IBAs don't have any legislative protection.