Osprey Nesting Behavior
Naturally Curious is back! Different ecosystem (western vs. eastern Vermont) but same curiosity! This week’s posts are going to be devoted to the nesting behavior of the Osprey — the only raptor that plunge-dives feet first to catch live fish as its main prey source.
Ospreys nest within six to twelve miles of water (usually much closer). The male collects most of the nesting material and brings it to the nest site where the female arranges it. Sticks as large as an inch-and-a-half in diameter and three feet long are collected from the ground, or (less commonly) snapped off a tree while the Osprey is in flight. Nest-building continues throughout the incubation of the eggs as well as the brooding period — even if a nest fails, Ospreys will continue to add material to it.
Although nests built on platforms are relatively small, those built in trees or on the ground can be 10 -13 feet deep and 3 – 6 feet in diameter (the largest nests are most likely the result of several generations of nesting Ospreys). The shape of an Osprey nest changes during the breeding cycle. When the eggs are being incubated, the nest is bowl-shaped. After hatching the nest flattens out, but a rim of sticks is maintained. By the time the nestlings fledge (around 50-55 days) the nest is often completely flat.
Ospreys will reuse their nest year after year, saving themselves time and energy which allows earlier laying and more surviving young. Birds whose nests fail are likely to build alternate nests and use them in subsequent years. (Birds of the World Online).
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