The white-tailed sea eagle is Germany’s largest native bird of prey - with an eventful history. Today, the eagle is still found in Scandinavia, Central Europe, from south-eastern Europe to Greece and Turkey, and eastwards across Russia to the eastern coasts of North Asia. In the past, it was also widespread in large parts of Western and Southern Europe and as far as North Africa. While populations are recovering after drastic declines in Central Europe and the Baltic States, for example, the white-tailed sea eagle is considered extinct in Italy, Switzerland, France, Spain, Portugal, the Faroe Islands, Corsica, Sardinia and Ireland.
In the second half of the 20th century, the white-tailed sea eagle was almost extinct in Germany due to human persecution and the consequences of the insecticide DDT. Since the 1980s, populations have been recovering after persecution ceased, the use of DDT was banned and effective protection measures for the nests during the breeding seasons were established in many places. New threats emerged, such as poisoning by lead-containing ammunition. The animals are also susceptible to infectious diseases: "White-tailed sea eagles feed on carrion and carcasses of hunting game, especially in winter, and also on waterfowl when available," says CRF seabird specialist Oliver Krone, a scientist at the Leibniz Institute for Zoo and Wildlife Research. "Of course, sick and weak animals are easy prey for the white-tailed sea eagle. As a result, these birds of prey are repeatedly exposed to viruses such as the avian flu and other pathogens in addition to lead (Pb) from hunting ammunition."
Dr. Krone and his friend and colleague Jānis Ķuze from the Latvijas Dabas Fonds (Latvian Fund for Nature) are committed to researching and protecting white-tailed sea eagles and other birds of prey in Central and Eastern Europe. Through ringing and health monitoring of the animals, they keep a close eye on the development of the populations and can make a well-founded assessment of health risks and conflicts with humans in particular.
Ķuze has equipped a white-tailed sea eagle nest on the Latvian Baltic coast near the town of Durbe with a webcam that allows the animals to be observed all year round (the webcam runs on solar power, occasional downtimes during low light are possible):
For white-tailed sea eagles, the year proceeds in a natural rhythm in which each phase of life is adapted to the prevailing conditions:
In autumn and winter, when the young of the previous year have left the parental eyrie, the courtship of the adult eagles begins. The eagles often call in duets. Often, the voices of the partners can be distinguished when the female calls in a lower pitch and the male in a higher pitch. In courtship flight, both birds can be seen close together or on top of each other, often turning towards each other so that the lower partner flies on its back for a short time. Occasionally they will then grab each other's feet and do a cartwheel. Winter is also the time when the eyrie is repaired or a new one is built. For this purpose, trunk or branch forks or old nests of ravens or birds of prey are chosen as bases. Dry branches up to one arm thick are picked up from the ground or broken off trees. The interior of the eyrie is padded with smaller branches and twigs of deciduous and coniferous trees and grass.
The peak of courtship is reached during the mating season in February and March. Mating takes place in the immediate vicinity of the eyrie on trees or on the ground as well as directly in the eyrie. Mating can be observed throughout the day, with an accumulation in the morning hours. The courtship ends with the laying of the eggs. The one to two, rarely three, white eggs are laid at intervals of one to three days at the end of February to mid-March.
Breeding in white-tailed sea eagles lasts an average of 39 days and is started with the first egg, the second following a few days later. Both partners breed, with the female often having the greater share. There is only one annual brood, subsequent clutches are very rare. Most young hatch between April and June. The young birds are hooted and fed by both adults, with very small pieces being torn out of the prey in the first days of life and carefully fed to the young birds. Later, the hunger and aggression of the young birds is so great that the adults sometimes only drop the prey into the eyrie and stay in the eyrie with the young eagles for as short a time as possible.
Six to eight weeks after hatching, spread over the early summer months, young birds of prey in northern Germany are ringed by bird of prey specialists like Oliver Krone and many other experts. This is not only a good opportunity to count the young birds and thus keep an eye on the population development, but also important for research: Dr. Krone takes blood samples, examines the birds for parasites or - in special cases - puts a transmitter on them to see exactly when they fledge and leave their parental territory. Recently, Dr. Krone and colleagues found out that young white-tailed sea eagles stay longer in their parents' territory than expected and that the eyrie protection periods, which protect the sensitive animals from forestry work, are too short. In addition studies on stress hormones in the feces of the eagles have demonstrated that roads and paths used by humans leading close to the nest increase stress in the eagles. Research and species conservation work hand in hand here.
In July and August, the young leave the eyrie, but remain in their parents' territory for several weeks to months. Between August and October, the young white-tailed sea eagles usually leave their parents' territory to find their own. In some cases, the young birds can be found hundreds of kilometres away just a few weeks after fledging. For about 4 to 5 years, the young eagles lead a vagabond life until they finally establish their own territory and become reproductively mature at the age of 5 to 7 years.
Essential life phases of the white-tailed sea eagle at the eyrie in Durbe, Latvia, are summarised in this film:
DO YOU WANT TO SUPPORT RESEARCH AND CONSERVATION OF THE WHITE-TAILED SEA EAGLE?
The Conservation and Research Fund supports scientists and conservationists such as Oliver Krone and Jānis Ķuze in researching birds of prey and their habitats and in implementing science-based conservation measures. Your donation will help Dr. Krone and Kuze in their work. 50% of the donated amount will go to the Leibniz Institute for Zoo and Wildlife Research for Krone's work and 50% will go to the Latvijas Dabas Fund for Kuze's work.
You can also support this initiative by donating directly to CRF via bank transfer:
Account holder: Conservation and Research Fund
IBAN: DE18 8306 5408 0005 2202 62
BIC: GENO DEF1 SLR
Subject: Sea eagles