Monitoring of the White-tailed Eagle population in the Middle Dnieper area
Monitoring of populations of rare Falconiformes is an important tool to organize protection of these birds. For this purpose we have developed the Monitoring Programme for the Birds of Prey of Ukraine. One of the Programme directions is long-term tracking of the White-tailed Eagle population.
We initiated the monitoring of the White-tailed Eagle population in 1992. That time numbers of this rare raptor in the Dnieper valley just started to restore and a discovery of every nest was a big event. Each year and expedition after expedition the territory of our studies expanded, and the numbers of the White-tailed Eagle also increased. At present, we know approximately 50 breeding sites of the White-tailed Eagle within regions of Chernihiv, Kyiv, Cherkasy, Kirovohrad and Poltava.
Annual monitoring includes occupation control of known breeding sites, search for new pairs, control of breeding success and productivity, organization of protection for breeding sites.
Results of these studies were reflected in a dissertation (PhD thesis) (Gavrilyuk 2002), and in individual publications (Gavrilyuk, Grishchenko, 1999; Gavrilyuk, Grishchenko, 2000; 2008 etc.). Over the 19 years we tracked 111 breeding cases. It is established that the average breeding success is 74%, i.e. approximately ¼ pairs breed successfully. Mostly the reason of unsuccessful breeding is hard to find out, however we know cases when these eagles did not breed chicks because of forestry activity in their breeding period or human disturbance.
The main factor affecting birds in breeding places is tree felling. Since eagles prefer nest-building in the oldest parts of forests, they are the most “tasty” for woodcutters. The most demonstrative is the fate of pairs nesting near the village of Kedina Hora (Zolotonosha district of Cherkasy region). Of the six known nesting trees four trees were cut down (see map). As a result of felling, birds were forced to build a new nest almost every year. Currently, the forest area in the breeding site is an alternation of felling and forest strips (fresh felling is not shown in the map). It is the strip, where birds arranged their nest at the moment (see photo). In the forest stand near the village of Lozivok (Cherkasy region) the felling in 2008 left the nesting tree on the edge of the clearing. The eagles, bred in this nest for about 20 years, were forced to move. Next year the nesting tree started drying (see photo). Such cases, unfortunately, are not uncommon. Totally, we know at least 6 cases of cutting down trees with nests of the eagles, of 3 pairs. More often eagles suffer from thinning, when a nesting tree itself is not cut down, but as a result of neighboring trees being cut the eagles finally leave their nest. In places, considerable damage is brought with spring fires in pine forests, after which areas with nesting sites of eagles dry out. At the same time the eagles are able to adapt to such conditions of nesting. We know five nests built on the edge of overgrowing clearings and quite well protected by eagles, therefore being not the most comfortable place for forest walks of nature lovers.
Most frequently the White-tailed Eagles hatch one chick (56% breeding success), a bit rarer – two (41%), and rarely – three chicks (3%). Average number of chicks per successfully bred pair is 1.49; average number of chicks per a pair which participate in breeding – 1.11. Chick mortality can be caused by cannibalism or loss of forage (2 cases); fall out of the nest (three cases).
In different years joint expeditions were participated with my friends, colleagues and relatives: N.N.Borisenko, G.P.Gera, V. N.Grishchenko, S. V.Domashevsky, A.V.Ilyukha, R.V.Salamatin, E.D.Yablonovskaya-Grishchenko and my wife Oksana, for all of whom I would like to express my gratitude. Also many thanks to S.V.Domashevsky, Yu.V.Kuzmenko, R. Sorish, which gave me additional information on productivity of the White-tailed Eagles.
If you have experience in observation and the desire to study one of the largest birds of prey in our region, join the program for population monitoring. Due to the fact that we have few people in our team, we manage to control only a part of the breeding population and cannot timely react to the threats that emerge near their nests. Your participation can bring the benefit to the study and protection of this species, which is in the Red Book of Ukraine.
Maxim Gavrilyuk
References
Gavrilyuk M.N. White-tailed Eagle in Ukraine: current status, biology and protection.– abstract of the thesis… PhD of Biology. – Kyiv, 2002. – 20 p.[in Ukrainian]
Gavrilyuk M., Grishchenko V. Breeding success of the White-tailed Eagle (Haliaeetus albicilla) in Ukraine in 1988-1998 // The Ring. (Abstracts of the 2-nd Meet. of European Ornithologists Union and 3-rd Internat. Shrike Symposium). – 1999. – V. 21, №1. – P. 142.
Gavrilyuk M.N., Grishchenko V.N. Current status of the White-tailed Eagle population in the Middle Dnieper area // Berkut. – 2000. – Vol.9, Iss. 1-2. – P. 28-38. [in Russian]
Gavrilyuk, M. N., Grishchenko, V. M. Productivity of the White-tailed Eagle breeding in Ukraine during 1988-2008 // Latest studies on Birds of Prey and Owls. Proceedings of the 3d International Scientific Conference «Birds of Prey of Ukraine», Kryvyi Rih, 24-25 October 2008. – P. 79-85. [in Ukrainian]