Sunday, September 03, 2006


We are still hearing the high pitched calls of Osprey, and see them landing on their favorite perches both sides of the river. Osprey live exclusively by fishing. They watch and wait on riverside perches quite a bit and also hover over the water just in case a fish resurfaces. The dives are spectacular and swift - they wouldn't catch many fish otherwise. They hit the water talons first and can go completely underwater. A young one this season was a hesitant diver - and it showed in his results. We estimate that most osprey are successful about one out of three dives. This youngster would stop at the beginning of his dive before finally heading down, by which time the fish, unaware of the osprey, would dive and escape the subsequent impact of the young osprey.

Our section of river is being shared by two pair of osprey this year. One pair nests in a cell phone tower a few miles West next to The Nature Conservancy’s Camassia Natural Area, while the others fly off upstream to points unknown. Male osprey do all the fishing during incubation and brooding. We can observe the birds much of each day during this period. Once the young are fledged, the adults seem to vary their hunting locations more, and are no longer present daily on our waterfront. The chicks are mature in 7 to 8 weeks, increasing over 30 times in size from hatching.

A major limiting factor for osprey is the availability of nesting sites. If all the good sites are already in use, then younger osprey may have to wait years to begin breeding. Why not erect a artificial ‘tree’ with a platform to encourage nesting? We have been asking ourselves this question for years! This has been done elsewhere, and its time to look into it seriously.

There are four subspecies of Osprey in the world. The American and Eurasian forms migrate, while the Caribbean and Australian forms stay year round in the mild climates they inhabit. Some Mexican and Florida populations also do not migrate. The wingspan can exceed 5.5 ft. (170 cm). Northern populations are larger than tropical non-migrant ones, and the females are much larger than the males. The smallest females are the size of the largest males. The biggest birds weigh in at 4.4 pounds (2 kilograms).

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