What does the future hold for the Polish White-tailed Sea Eagle?


Professor Mizera ringing female eaglet near Poznan 2006

Throughout the ages the “White Eagle” has been closely associated with the history of Poland. This important species was first adopted as the king’s emblem in times of Przemys II in 1295 and remains the State’s emblem today. A stylized image of a white eagle is present in the emblem (or crest ) of the Wielkopolska voivodeship as well as many cities throughout our region. Historians and nature experts argue as to which bird is actually depicted in the crest. None of the bird species is purely white, but the White-Tailed Sea Eagle is the only species with a snow-white tail and often very pale head. Today it is impossible to tell with any certainty. A fact supporting this theory might be that in many images of the “white eagle” the artists exposed huge bill and bare tarsi – an important feature that distinguish this species from any other eagle species. Besides in Middle Ages most cities were situated near rivers and lakes where fishing was a common occupation. There is little doubt that our ancestors had many opportunities for observing this species more frequently than any other eagles.


White-tailed eagles are very impressive when flying over-head.

The scientific name of the White-Tailed Sea Eagle Haliaeetus originates from two Greek  words: hals – meaning the sea and aetos – meaning the eagle. This origin is maintained in most European languages as the bird is often called “the sea eagle”, for instance Seeadler (in German), the White-Tailed Sea Eagle (in English), Aquila di Mare (in Italian). Even our southern neighbors use the name “Sea eagle – Orel morsky”. In Polish many different names were used in the past: orzel lomignat, orzel slepy, orzel bielec, orzel bosy, orzel morski, orzel bialoglowy, birkut.

The White-Tailed Sea Eagle (Haliaeetus albicilla L.) is the largest raptor species nesting currently in Poland. The wing span of a female extends to almost 250 cm, well over the arm length of a tall man. Females can weigh up to 5, or even 6 kilos while males are considerably smaller (respectively 215-225 cm and approx. 4 kg). Adult White-tailed Sea Eagles are distinguished from other native eagle species by an almost snow-white, wedge-shaped tail, partly bare tarsi (legs), a deep yellow bill and huge “plank-like” wings with fingers clearly visible when soaring allowing for easy identification even from a distance. Juvenile birds are rather dark and become paler with age. When they reach the age of 5 years they begin to resemble adult birds. White-Tailed Sea Eagles are long-living – in the wild they can reach an age of 30 years, 42 in captivity. They form permanent pair bonds throughout their lives.

In the beginning of the 20th century there were only 2-3 breeding WTSE pairs in the Wielkopolska region of Poland. This position did not change much until the 1960’s. A serious threat for the population’s development was a common use of DDT in agriculture. This resulted in egg shell thinning causing eggs to break and much reduced reproduction. The breakthrough came in the 1970’s when the use of DDT in Europe was banned.


The same eagle rung by Professor Mizera in 2006, photographed again in 2008, a distance of 85 Km  from where it had been originally rung in 2006.

In 1984 Polish Authorities introduced further steps to improve the breeding success by establishing ‘exclusion zones’ around nests. These important conservation measures were implemented at a Polish Ministry level. A 200 meter exclusion zone strictly protected all nests throughout the year and additionally during the breeding season (from 1st of January till 31st of July). In addition no forestry activity was allowed within the 500 meter radius of any nest. These revolutionary regulations protected all breeding territories providing the peace and security necessary for nesting pairs to successfully raise their chicks. The number of pairs increased to 8 in 1980, rising to 80 pairs by the beginning of the twenty first century. At the present times there are at least 100 breeding pairs in the region and between, 1300-1500 pairs in the whole country, mostly in Pomerania and Masuria.

The region with the highest density of breeding pairs is the Sierakow Landscape Park, with 9 active nests of White-Tailed Sea Eagle. Here on a daily basis eagles can be observed fishing at almost every fish pond and over many lakes. During winter many of these birds concentrate along the Warta river near stretches of unfrozen water. Groups of eagles also gather for the night in one place, where over a dozen of individuals can be observed perched together in one tree. Such observations are always spectacular. White-Tailed Sea Eagles nest also in other Landscape Parks: Perkowsko-Czeszewski – 3 pairs, Rogaliski – 2 pairs and Dolina Baryczy, Nadwarciaski, Promno, Puszcza Zielonka, Przemcki and Pszczewski – 1 pair each. The citizens of Poznan can observe the birds at the Warta river near Wilczy Myn.

The White-Tailed Sea Eagle has always had a close relationship with water, where they mainly hunts for prey – mainly fish and water birds for example coot and duck. Rarely does the White-tailed Eagle catch mammals, preferring in the winter time to feed upon carrion which is the major part of this eagles diet. Adult bird consumes 500-800g of food daily. Sometimes they fast for a few days to eat up to 1,5 kg of meat later. The increase in the number of White-tailed Sea Eagles in Poland has forced many pairs to occupy sub-optimal territories, away from water. In such places their diet comprises of small mammals (hares, young roe-deer, fox and wild boar piglets) or even roving domestic cats. They use different hunting techniques – usually they perch on a tree near water in search of their favorite prey – birds and fish. Sometimes two birds can be observed in cooperative hunting. The cooperation takes place when attacking a flock of coots or ducks which in a group can effectively defend themselves against a single attacker by means of synchronized diving beneath the water. But when resurfaced after the attempt of the first attacker, they are often attacked for a second time by another eagle causing the flock to scatter, which then facilitates catching the targeted prey. Sometimes one of the raptors hangs in the air above a flock and another one circles nearby waiting for a chance to catch a surprised individual. A spectacular way of food is cleptoparasitism – White-Tailed Sea Eagles steal food from other birds, even of the same genus. This behavior if often observed in autumn and winter especially near fish ponds where the raptors gather in larger numbers

Tree-nestTree Nest Measuring a staggering 4m high. Courtesy of Tadeusz Mizera. 

White-Tailed Sea Eagles build their nests in trees. The nest is always an impressive structure located in the crown of an old tree. Newly built nests are approximately 1 meter in diameter and 0.5 meter in depth. Nests are used by a single pair of eagles for many years, new branches being added each year. Nests have been recorded as high as 4 meters and 2,5 meters in diameter, and can weigh up to a ton. Many nests in Wielkopolska (Greater Poland ) have been used in succession for over ten years. If not disturbed, new nests are built in the same part of the forest. The best example of how these birds are attracted to traditional breeding sites is a case where one pair re-occupied a territory on an island in the Sieraków Landscape Park after an 80-years absence. White-Tailed Sea Eagles build nests from scratch, rarely adapting nests of other bird species (for example Black Storks, Common Buzzards or Goshawks). Abandoned White-Tailed Sea Eagle nests, on the other hand, are often used by Eagle Owls, Black Kites, Mallards or even smaller birds like Hobbies. Inside active White-Tailed Sea Eagles nests small birds also build their home – White Wagtails, Tree Sparrows, Starlings and Tree-creepers. They all profit from the “protection” of their impressive host.

All bird species build nests in the spring. However, in the case of White-Tailed Sea Eagles this process begins in late autumn. Some pairs build new nests, others only renew old ones with fresh branches. In winter adult birds remain within in their territories while juvenile birds migrate to Central or Western Europe. Some juveniles can also remain within their parents’ territories. In autumn most juvenile birds can be observed near fish ponds where groups of several or even several tens of individuals feed on fish trapped in shallow water.


Nests containing triplets in parts of Poland are fairly common due to an abundance of fish. Courtesy of Tadeusz Mizera, image taken near Poznan by Jakub Pruchniewicz. 

White-Tailed Sea Eagles lay their eggs very early, between the beginning of February and end of March. The clutch consists usually of 2-3 eggs, exceptionally 1 or 4. Both parents incubate their eggs, female more often and always during the night. Eggs are incubated for 38 days. Since White-Tailed Sea Eagles hatch from the first egg laid, the hatchlings come to life asynchronously. The age difference between the youngest and the oldest can reach one week. This age difference can cause difficulties for the former’s chance of survival, known as the Cane and Able syndrome, where the youngest sibling is often killed by the older sibling; a common and well documented occurrence in Golden Eagles. Clutches of three occur every year especially in abundant food supply territories. One nesting pair with two chicks brought to nest 116 kg of fish, of which each chick received 52 kg and the rest 12 kg was consumed by the adults. For its own purposes an adult White-Tailed Sea Eagle needs 0.5 kg of food daily.

The chicks remain in nest for 10-12 weeks. Young males leave the nest slightly earlier than females. During 5-6 weeks fledged juvenile birds remain under parental care and are fed where necessary. Throughout the first 4-5 years of their lives these sub-adult birds lead nomadic lives until they reach maturity. At the age of around 6 they mate and form a solid relationship for the next 20-30 years. White-Tailed Sea Eagles are a good example of a monogamous partnership. New individuals are acceptable only after death of one partner. With sufficient number of non-breeding birds such a loss can be complemented within a few days, but sometimes this process can take several weeks.

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Male eagle flying just metres above pond on a fishing trip

White-Tailed Sea Eagles in Greater Poland are regularly ringed at the nest as nestlings. Chicks receive two rings: the standard ornithological one and a color one for observation. Each ring has its individual and unique code. The same methodology is undertaken within the whole Europe, and everybody is invited to join the research program. It is as easy as taking a photo of a ringed bird and sending it to the Ornithological Station in Gdansk (stornit@miiz.waw.pl). Thanks to such data the birds’ biology is better understood enabling implementation of more efficient protection measures.

The oldest ecological organization involved in active conservation of the White-Tailed Sea Eagle and other raptors was initiated in Poland in 1981 by the Eagle Conservation Committee (KOO). Their members regularly monitor nests, research the breeding efficiency, ring the chicks and support both foresters and Regional Directorate for Environmental Protection in implementation of protection zones. More about KOO activities can be found on the web page: www.koo.org.pl.

What does the future hold for the Polish White-Tailed Sea Eagle? When the Capercaille, Black Grouses, Bustards, Godwit, Lapwing and dozens of other species die out before our eyes the White-Tailed Sea Eagle, against all the odds, has somehow managed to adapt to a transformed environment. Heavily persecuted in the past, the species was forced to nest in the deepest parts of Poland’s largest forests. Fortunately further improvements to legal protection, banning the use of DDT together with the introduction of protection zones around nests have all helped to improve reproduction figures. Now new pairs regularly occupy small forested areas. Today Polish White-Tailed Sea Eagles do not only nest within national parks or protected areas, their territories now extended into many commercial forests throughout Poland. There is now excellent mutual cooperation between foresters and ornithologist in Poland, this partnership has resulted in improved and more effective protection for the White-tailed Eagle producing the population increases we see in Poland today.


Male White-tailed eagle flying towards photographic hide located 9 metres above the ground.

Please consider this, when walking outside our cities it would be a good idea to take your binoculars just in case you get an opportunity to admire this majestically soaring Jewel now established within our Polish landscape.

This paper has been republished with the permission of the two co-authors, Tadeusz Mizera and Krzysztof Chomicz, and forms part of a complete photo album of 44 pages,  and includes 70 picture taken in the field, many of which are unique.

ISBN  978-83-7518-757-1

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