Wintering of the White-tailed Eagle at the Dnieper near Kaniv in 2011-2012

July 23rd, 2012 Posted in Photos, Wintering

A non-freezing area of the river downstream from Kanivska Hydropower Station is one of major wintering sites of the White-tailed Eagle at the Middle Dnieper. Due to HPS working in a peak regime there are regular changes of water levels in the tail-water. It leads to constant break of ice carried away by water flow. Even in heavy frosts unfrozen water areas still remain, and during water drainage the ice breaks again. A continuous solid ice cover had no time to form. It is a site of usual wintering for ducks, first of all the Mallard, Merganser and Goldeneye as well as gulls and some other birds..

Photo by V.N.Grishchenko

The White-tailed Eagles began wintering near Kaniv immediately after start of HPS exploitation. In the 1970s-1980s their numbers did not exceed 4-6 birds (Loparev, Grishchenko, 1992), quickly increasing since that time. Recent years the site held 15-20 individuals, sometimes more. Maximum numbers of these eagles in this wintering area were counted on 3.01.2009 (26 birds) and 17.02.2011 (24).

Annual counts of the White-tailed Eagles and other wintering birds we provide near Kaniv since 1987. The eagles which reached 5 years age were considered as adults. The age was identified by plumage coloration (see Gensbol, Thiede, 2005). Usually, the count route went from Kanivska HPS to Lake Prosered or the Ros river mouth (12 to 18 km) depending on the length of unfrozen the area.

Maximum numbers of the White-tailed Eagles for the all observation years were recorded in the winter of 2012. At first, wintering bird numbers was small (Table). December and the first half of January were warm, without ice cover on water bodies. Heavy frosts in the second half of January brought about intensive migration of wintering birds and concentration of others on unfrozen areas. 28.01.2012 we counted the highest numbers of the wintering eagles – 29 ind.

In late January there formed a wintering group of the White-tailed Eagles. Its composition and numbers kept more or less constant until early March. 6-7 adult birds were registered in counts. Apparently, they were local eagles wintering near their breeding territories. In the areas, adjacent to the wintering site, 4-5 pairs breed annually. Adult eagles often were seen in pairs, squawking and played in the air.

The eagle’s migration likely started on 10.03.2012. Their numbers at the Dnieper increased twice.
112.03 we registered a record number – 46 birds, all juveniles. Presumably, adult birds were already on nests. Only one adult eagle registered in counts flew to the Dnieper from the side where nests were located (Zmiiny islands of Kaniv Reserve). The eagles were dispersed along banks, most of them sat on trees or on the ice as single birds or in groups of 2-4 ind. Some birds were flying. Probably there were even more of eagles since those stayed in inner channels in distant parts of the islands were underestimated.
The next very day numbers of the White-tailed Eagles notably decreased. They dispersed, and a part of them probably roamed away. Again only one adult eagle was counted, from another pair – from Shelestiv Island. Next days numbers were dropping more and more i.e. birds were moved further.
It is interesting that young eagles formed more or less permanent groups on wintering. A group of six birds were several times recorded at the wharf “Tarasova Mountain” and Sobachyi Island. A group of 4 birds were seen in the southern part of Shelestiv Island.

Wintering White-tailed Eagles mostly feed on fish. More often their prey consisted of zander, pike, bream, roach. In spite fish abundance, the hunting is not an easy business for the eagles. Majority of strikes are unsuccessful. Sometime you can observe curious situations. One of two eagles, trying to catch a zander, plumped in water and lay there for a minute (photo). Then easily flew off. However even a captured fish can’t guarantee good lunch. We saw when a fish, already lifted in the air, slipped out of claws. As a rule, the eagles didn’t try to catch it again. Obviously they know from experience that such fish immediately went into deep waters and useless to look for. And sometimes eagles even cannot lift their prey. Once we watch an adult eagle swimming to the bank for about 50 m, its wings flapping. Then successfully dragged a big bream out of the water. More difficult and therefore rarer prey for the White-tailed Eagle are ducks. All observed hunting attempts failed. Seeing a descending raptor, goldeneyes and mergansers gather in a dense flock and fly off. Therefore only a weakened or careless bird may be caught. Sometimes they also attempted to catch large animals. The safeguarding personnel of the protection service in Kaniv Reserve observed in March 2012 a White-tailed Eagle attacking a young wild boar. Some cases are also known when these eagles attacked vagrant dogs. They readily eat carrion, often making nearby large bird concentrations. 7.03 at the shore of Sobache Lake 19 birds gathered to eat remains of large fish.

Wintering White-tailed Eagles rather calmly react on human presence. You can see birds sitting on ice at the distance of 100-200 m from fishermen. In February several times the eagles were seen sitting on trees by the road along the Dnieper riverbank. They didn’t pay any attention to the passing cars and allowed men to approach up to 50-100 m.

Table

Results of White-tailed Eagle counts
Date Adults Juveniles Total
25.12.11 2 1 3
07.01.12 3-5
23.01.12 6 9 15
28.01.12 6 23 29
8.03.12 4 18 22
12.03.12 1 45 46
13.03.12 1 31 32
16.03.12 3 15 18

V.N.Grishchenko

References

Loparev S.A., Grishchenko V.N. (1992): Winterings of the White-tailed Eagle at the Middle Dnieper. – Berkut. 1:62-64. [in Russian]

Gensbol B., Thiede W. (2005): Greifvogel. 4. Auflage. Munchen: BLV. 1-415.

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