page_title: White-tailed eagle
section_title: Hatching, development and fledgling
hierarchical_section_title: White-tailed eagle / Breeding / Hatching, development and fledgling
caption_attribution_description: Haliaeetus albicilla, nestling
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: In 1983, it was listed that brood size is one 56.5% of the time and two 40.8% of the time in 8 studies from different parts of the range; only 2.5% of these studies had a brood size of three and only 1 from Norway was a brood size of four recorded. From 14 studies, the mean number of chicks in a brood may range from 1.1 in western Germany to 1.9 in southern Kazakhstan, with average overall brood size of 1.52. However, these datasets may be skewered lower than natural brood size as a majority these are from the mid to late 20th century when pesticide use considerably lowered the mean number of hatchlings in many parts of the range. New hatchlings will weigh about 90 to 100 g (3.2 to 3.5 oz) but in Hokkaido new hatchlings were surprisingly notably heavier at 110 to 115 g (3.9 to 4.1 oz). The sex of nestlings can be identified using field methods, or using DNA. Initially, the hatchlings have a creamy white down which is longest and whitest on the head and often dirty grayish on wings and rump. Before they start walking about the nest, their underside may have several bare patches. The nestlings first become audible at around 2 to 3 days and have become active enough to move around the nest and excrete over the nest edge by 10 days old. The initial down is replaced by a thick woolly coat of longer, coarser grayish down, which is usually darker on the crown, underparts and flanks. The legs and cere at this young nestling age can range from pinkish to pale yellow. By about 30 days the first feathers poke through the down. The eaglets can feed themselves starting at 35–40 days. At 6 weeks (40 days) they are more firm on their feet and between this and the following week feathers take over the down, with patches of down remaining but usually gone by week 7. Wing flapping begins only when the wings are partially feathered at 42 days. Around seven weeks of age, the eaglet is more alert and stronger and frequently manipulates sticks and walks more so. At 8 weeks only the long feathers of the wing and tail have yet to develop fully and eaglets tend to start exploring the surrounding branches. The eaglets will attempt their first flight at about 70 days and will usually be flying well by about 90 days of age. Fledgling occurs around mid- to late July in Norway, and about 3–4 weeks later in Russian White Sea.
  The female of the white-tailed eagle pair seems to do all the brooding early on and will be especially reluctant to leave the nest as well. Thereafter, at 14 to 28 days, brooding behaviour by the female gradually declines. The male may start to brood occasionally around this time period but will not do so at night.  Females may sit on the nest or shelter the fledglings from rain even 28 days after fledging but usually such behavior is much reduced. Chicks may be fed as many as 11 times in 24 hours by the female who usually dismantles prey brought by the male. To 28 days, male continues to do most of the prey capture but thereafter female does much of it and both parents begin to leave kills on the nest for the eaglets to consume. As the chicks grow older, favored food often switches from fish to birds to meet their increasing food requirements as well as prey behavior as waterfowl may be flightless during eclipse. Caches are often depleted quickly late into nestling development. At start of fledgling, 4-5 carcasses may be brought in a week but by the end only 1 to 2 are usually brought, probably to encourage the young to start their own prey captures. After leaving the nest, the young usually stay nearby for another 35–40 days and may still be largely fed by their parents but gradually learn to take their own prey. In continental Europe, the young eagles are gone from the nest as early as early July to about August 10 and fully independent by late August. In this late summer stage, they may learn quickly to feed on stranded fish or to capture ducks flightless in eclipse. Juvenile eagles may remain for a long time on their parents range and apparently are not resented or repelled even to the ages of 1 to 3 years. However, usually 
caption: A large nestling in Brandenburg, Germany.
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