Wildlife of the James

Osprey Nesting

Pandion haliaetus

Osprey on the James River are busy raising the next generation of these beautiful birds. In what can only be an exhausting five month period, osprey migrate north from their winter range to begin creating or perfecting a nest in April, lay and incubate eggs, and then feed ravenous hatchlings who put on their adult weight very quickly.

Much like a larger land mammal that can also be spotted taking to the water in summer, the osprey male spends this season trying to impress and please the female. As a young male, he must compete for the best nest site over water and near good fishing. When the females arrive from their migration, he performs an elaborate, diving aerial dance. If he succeeds in attracting a mate, she will spend most of her time incubating the eggs and protecting the chicks. Thus, the male must hunt consistently to keep her fed. Indeed, if the male proves inadequate in his attention and competence, infidelity by his mate can result. On the other hand, if the pairing is a happy one, it can last for life. Despite this, the male osprey is known to gobble down a portion of his catch before bringing it back to the nest.

Every osprey descends from a long line of fish-catching specialists and so finds itself equipped with especially ingenious feet. First, the bird’s foot pads are covered in tiny spikes for holding onto slippery fish. With dinner thus secured, the osprey uses its unique reversible toe to point the body of its prey ahead in an aerodynamic position. Next time you spot an osprey with its catch, look closely at how it carries the fish.

Osprey lay up to four eggs in a clutch. A trick of evolution common in birds of prey provides insurance for the parents against total reproductive failure in lean times; the chicks hatch sequentially, with the first chick emerging up to five days before the last. If food becomes scarce, the smaller chicks are unable to compete successfully with the larger young. This extreme sibling rivalry ensures that some of the osprey’s offspring will grow up strong and healthy even as scarcity threatens the brood.

After the young have fledged and begun to learn to hunt, the female osprey will leave the family unit first and begin her flight as far south as Brazil. Males stay with the fledglings longer, and then migrate south as well. Males winter in separate areas in Florida and the Caribbean generally north of the females range. One is tempted to speculate that the success of a life-long pairing might be fostered by this separate winter retreat!

For us James River bird watchers, the ospreys’ winter travels to the south remain a mysterious time. After seeing their busy lives as parents, we can hope that along some tropical shore they have some down time.  Thanks to conservation efforts and the banning of the pesticide DDT in 1970, we can now rest assured that these graceful hunters will return to us on the James on wings of spring.

Gabe Silver
JRA Environmental Educator

Want to learn more?

Cornell Lab of Ornithology                 www.allaboutbirds.org
Encyclopedia of Life Project               www.eol.org