page_title: Reproduction and life cycle of the golden eagle
section_title: Reproductive success
hierarchical_section_title: Reproduction and life cycle of the golden eagle / Reproductive success
caption_attribution_description: Golden eagles are birds of prey common seen in Saskatchewan. They typically feed on small mammals such as ground squirrels, rabbits and other birds such as grouse.
context_page_description: Golden eagles usually mate for life. A breeding pair is formed in a courtship display. This courtship includes undulating displays by both in the pair, with the male bird picking up a piece of rock and dropping it only to enter into a steep dive and catch it in mid-air, repeating the maneuver 3 or more times. The female takes a clump of earth and drops and catches it in the same fashion. Small sticks may also be used in this display. Compared to the bald eagle, golden eagles do not repeat courtship displays annually and rarely engage in talon-locking downward spirals.
  Golden eagles typically build several eyries within their territory and use them alternately for several years. Their nesting areas are characterized by the extreme regularity of the nest spacing. In 9 studies of annual nest spacing, the average minimum distance between nests range from 16 km apart in Norway to 8 km apart in Switzerland. Nests in Scotland may found at anywhere from 10 to 65 pairs per 1,000 km², with an average of over 20 pairs found per area.
  In much of continental Europe, densities of less than 10 pairs per 1,000 km² are typical.
context_section_description: Generally breeding success seems to be greatest where prey is available in abundance. In Central Utah, 57% of eggs successfully hatched out of 87 eggs from 44 clutches. In Idaho, 65% of 282 eggs from 145 clutches successfully hatched, and in Montana, 86% of 28 eggs from 14 clutches hatched. In Scotland, the highest breeding success of golden eagles was in the Eastern Highlands where heather moorland still abundant, bearing plentiful red grouse and mountain hare. The jackrabbit follows a 10-year cycle where it peaks and crashes. In Idaho, 100% of observed nests produced at least one fledgling when the jackrabbits peaked in the late 1970s through the early 1980s and then at the low point in the mid to late 1980s, the nests produced on average only 0.2 fledglings. Similarly, in central Utah jackrabbit numbers were correlated with average number of young reared by 16 golden eagle pairs. Here the average number of young ranged from 0.56 in 1967 to 1.06 in 1969 to 0.31 in 1973. In Sweden, nesting success rose noticeably in years where the hunting bag (estimated quantity of prey) rose. After viral hemorrhagic pneumonia (VHP) killed off many rabbits in Spain, the average breeding success of golden eagles in Northern Spain dropped from 0.77 in 1982–1989 to 0.38 by 1990–1992. In Belarus, the average brood size is reportedly 1.8 whereas the average number of fledglings is 1.1. As previously mentioned, adverse weather can affect breeding success. In the exceptionally stormy and cold spring of 1984 in Montana, 71% (10 out of 14) studied nests failed. A long period of exceptionally rainy, cold springs in Scotland reportedly resulted in a 25% reduction of fledging pairs being produced. Rather than directly killing the nestlings, stormy, wet weather probably causes the most harm to productivity due to the hampering of the parents' ability to hunt. In arid areas, heavier rainfall has the opposite effect and actually improves nesting success. Rainy years in the deserts of Israel, which provide more brown hares and chukars to hunt, were more successful years for breeding. While siblicide is estimated to claim about 80% of second hatchlings among golden eagles, in some parts of the range, the survival rate in successful nests is higher. In ideal habitats in North America (Northwestern United States and Alaska), 38 to 56% of nests produce a second fledging. Populations at northern end of range have smaller broods (brood size being about 12% smaller) and produce fewer fledglings (population productivity being about 25% smaller) than those in temperate areas, as has been revealed by contrasting studies of Alaska to Idaho.
caption: Golden eagle – nest scene reconstitution
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