page_title: White-tailed eagle
section_title: Nesting failures and longevity
hierarchical_section_title: White-tailed eagle / Breeding / Nesting failures and longevity
caption_attribution_description: Deutsch: Im Gostynin-Wloclawek-Landschaftspark an der zentralen Weichsel überwintern zahlreiche Seeadler (Haliaeetus albicilla). Die Region ist ein natürliches Habitat für diese eindrucksvollen Vögel. Die Zahl der Adler ist so hoch, dass sich bei der Beutejagd mitunter recht aggressive Rangeleien um ein Beutestück ergeben. Manchmal sind die Flugfiguren der kämpfenden Vögel akrobatisch. Hier bekämpfen sich ein adulter (unten) und ein juveniler (oben) Adler. English: In the Gostynin-Wloclawek nature reserve (Poland) several white-tailed eagles (Haliaeetus albicilla) overwinter; this is a natural habitat for these gigantic birds. The number of eagles in this habitat is high enough to observe occasional aggressive wranglings over some prey. The fights may become acrobatic at times. Here a juvenile bird (top) is being chased away by an adult bird (yellow beak, below). Photo taken in October 2017.
context_page_description: The white-tailed eagle is a very large species of sea eagle widely distributed across temperate Eurasia. As are all eagles, it is a member of the family Accipitridae which includes other diurnal raptors such as hawks, kites, and harriers. One of up to eleven members in the genus Haliaeetus, which are commonly called sea eagles, it is also referred to as the white-tailed sea-eagle. Sometimes, it is known as the ern or erne, gray sea eagle and Eurasian sea eagle
  While found across a very wide range, today breeding as far west as Greenland and Iceland across to as far east in Hokkaido, Japan, they are often scarce and very spottily distributed as a nesting species, mainly due to human activities. These have included habitat alterations and destruction of wetlands, about a hundred years of systematic persecution by humans followed by inadvertent poisonings and epidemics of nesting failures due to various manmade chemical pesticides and organic compounds, which have threatened eagles since roughly the 1950s and continue to be a potential concern. Due to this, the white-tailed eagle was considered endangered or extinct in several countries.
context_section_description: Normally white-tailed eagles succeed in raising 1-2 from a clutch of 2 and 2 from a clutch of 3. The average breeding success seems to be about 1.1-1.6 young per annum (i.e. 45-48 young from 40 observed cases, with 16 failures) (1.6 young per pair in 93 recorded Norwegian nests). About 33% of nesting attempts will fail to produce any young, and this is sometimes as many as 75% (at times of heavy persecution or pesticide use). Beyond manmade threats to white-tailed eagle nestlings, starvation and nest collapse are considerable causes of nestling deaths. Natural threats in the nest may also include siblicide (or “cainism”) wherein the largest nestling behave aggressively and gradually kill their smaller sibling, which is often consumed. Despite claims to contrary, siblicide in white-tailed eagle does occur with some regularity in some parts of the range, from Germany to Hokkaido although is certainly less frequent than in some eagle species, including the golden eagle. Single cases were reported in the White Sea and Iceland, and it may occur situationally as in many birds of prey when prey populations are low or prey capture is inhibited by poor weather. Siblicide can be avoided in white-tailed eagles with manipulative techniques, which may include taking out and hand-rearing the runt, put a chick into a nest with slightly younger brood which it is about the same size as, or taking the first egg out and putting it back in later so it develops evenly with its younger sibling. Surplus chicks are sometimes removed from nests to use in reintroduction programs in areas where the species has died out. If left in the nest, they often die sooner or later, as with most large eagles. In such programs the birds are raised in boxes on platforms in the tree canopy and fed in such a way that they cannot see the human supplying their food, until they are old enough to fly and thus find their own food.
  Known natural predators of white-tailed eagle eggs and nestlings include red foxes, martens and bears, especially if nesting in overly accessible rock formations, while wild boars have been recorded eating eggs and nestlings that’ve fallen out of the nest too early. Avian predation, overall a seemingly rare occurrence, of white-tailed eagle eggs and nestlings have been reported as crows, common ravens and western marsh harriers, which are likely to succeed in cases where nest attendance is low or if successful in driving away the parents via fierce mobbing. Furthermore, Eurasian eagle owls have been reported to prey upon "fairly large" nestlings of white-tailed eagle in nighttime ambushes. Many juveniles do not survive their first year post-independence. In the 1970s, an average of 56% banded first-year white-tailed eagles in Norway, Sweden and Greenland were found dead, most often having been shot. In eastern Germany, of 194 white-tailed eagles found dead between 1946 and 1972, of those where cause of death could be determined, 39% had been shot, accidents (especially powerlines) accounted for 6%, territorial disputes 7.5% and conservatively 13% were from poisoning. It is estimated that the survival of those that reach adulthood at 70%. Another estimate of average lifespan for those who reach adulthood is just over 12 years. Widely reported individuals have been found to live for 25 years or more, Another estimate of mean lifespan (presumably without persecution) is 21 years. At one point, the oldest banded white-tailed eagle known in the wild known lived for 27 years. However, a wild eagle of the species was subsequently recorded to life for 33.1 years. White-tailed eagles in captivity have lived for more than 40 years, though their exactly captive longevity record is not known.
caption: An adult and a juvenile white-tailed eagle fighting.
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