Nest sites may be on cliff faces, dirt banks, in deciduous or coniferous trees, on the ground or on man-made structures. The choice of location varies geographically and clearly depends upon the availability of certain features. Cliff faces and large trees are the most commonly-used nest sites and some pairs will alternate between the two types. Where possible, sites which avoid either excessive heat or excessive cold are chosen. Southerly-facing sites at northern latitudes are warmer and northerly-facing sites at southern latitudes are cooler and there is some evidence to indicate that there are preferences shown where the opportunity arises. Tree nests are often near the edges of openings such as fields or clear cuts. Nest sites may be used for many years by a succession of occupants.
Typically, the nest is comprised of large, dry sticks that are gathered from the ground or may be broken from a tree. The nest lining material varies geographically but it is of much finer material than the structural items. Rootlets, eucalyptus leaves, moss, rabbit fur, shrub twigs, yucca roots, dried grass, and conifer branchlets have all been used to line nests. Curious items that have been incorporated into nests include cow bones, deer antlers, barbed wire, burlap bags, rags, paper and rubbish and even a hat. Nests vary in size but may initially be around three feet (0.9 meters) in diameter. Over the years, additions and repairs may result in nests as large as eight feet (2.4 meters) in diameter. The height may vary from several feet and beyond. The building of several nests is common with up to 12 nests being built by a single pair. Pairs averaged six nests in Idaho.
The clutch size varies from one to five (rarely) and more typically two to three eggs. They are about 3.1 inches (78.7 millimeters) long and 2.3 inches (58.4 millimeters) wide. The base color varies from white to cream and is variably spotted or blotched with browns, chestnut-red, or pale gray. Some may be almost unmarked and they are non-glossy. The laying interval is likely between 90 and 120 hours with incubation starting as the first egg is laid. Although the Golden Eagle is single-brooded, replacement clutches may be laid in the event of loss of the original. The interval before relaying varies from 24 to 28 days. Egg-laying may begin during February at the extreme southern parts of the range while in the north, egg production may not occur until mid-June. March and April are common months for laying by non-migratory birds.
Incubation is primarily by the female with food being brought to her by the male. She feeds at a nearby plucking site. The male will relieve the female for periods during the afternoon but she probably does all of the incubating during the evening hours. Brooding of the young is by the female and occasionally by the male. Fresh greenery is brought to the nest by both sexes.
The incubation period is from 41 to 45 days, although it is variably reported in the literature. Earlier estimates of 30 to 35 days were likely incorrect. The long interval between the laying of each egg leads to young of different sizes. Fledging occurs at 72 to 84 days, but has been reported as 59 to 70 days. At about seven days, the nestling can sit up, stretch its neck and chirp for food. At 14 days, crawling is possible and the white down is well-developed. By 28 days, the chicks can waddle, hiss and raise their wings in threat displays. By 42 days, hostile threat capabilities are much better developed and the young can feed themselves. At 49 days, they will use both feet and wings in order to move around. By days 56 through 65, strength increases, mobility improves continually and vocalizations have become more complex. Mantling over prey is evident. The female sleeps away from the nest from about day 40 onwards. Siblicide is well-documented in the Golden Eagle, and it generally occurs when the young are less than 21 days old.
Flying young remain dependent upon their parents for about 11 weeks after fledging. In migrant populations, the entire family may begin migration together whereas in more southerly resident populations, the young may remain well into the fall or winter near the parents' territory. The existence of what appear to be family groups on the winter range suggests that the families could stay intact until the start of the next breeding cycle.
The breeding success for Golden Eagles is variable and probably follows major food source fluctuations. The number of young fledged per nest varies from 1.2 to 1.8 in different parts of the United States.
#Which species lays this egg?;question\Q32\Q32.wav
