Nesting ospreys provide glimpse of family life

Posted May 29, 2009, at 11:01 p.m.

The pair of ospreys perched in the nest, aware of everything going on around them: the boat traffic to and from the small marina, the walkers and joggers passing along the footpath on shore, the people hanging out on the pier and the gulls flying over the bay. There was little that escaped their attention, yet nothing elicited a reaction from the birds.

Until, that is, another osprey glided into view and began circling about 100 feet above the nest. The male of the pair immediately launched itself from the nest and began an air patrol below the interloper. Both filled the air with their characteristic, high-pitched whistles.

Eventually, the intruder moved out across the bay, and the resident male flew to the bow of a docked oil tanker. It alighted on the ship’s railing and seemed content with its lookout post. Although two more ospreys appeared, they were very high up and the male did not appear to take them as a challenge.

Earlier in the season, I had seen and heard the male perform his territorial “sky dance,” an undulating rollercoaster maneuver that is often done as he dangles his feet. At times he may clutch nesting material or a fish in his feet as he performs this display, and may hover in the air, appearing to almost stall and fall from the sky.

At one point I had come upon their location and observed an interesting tableau. One of the birds — most likely the female — was in the nest. She held her body horizontally and seemed very intent as she intermittently uttered short, soft whistles. Her attention was focused on the male, who was perched on a piling nearby, devouring a fish he held clasped in his feet.

Eventually, the male flew to the nest with less than half of the fish, which he gave to the female; she took it and flew out to the piling to consume it.

I’ve since met other osprey enthusiasts in the area who’ve observed this same situation. There the male would sit, eating his fish, while the female grew increasingly louder and more impatient in demand for her share.

According to the “Birds of North America,” species account, once osprey courtship begins the male is responsible for providing food to the female until the young fledge. I read this short passage in the account with interest and amusement:

“Older males….fed more fish to their mates than did males [less than five] years old, mostly because they shared their catch more equitably with mates. Rates of feeding had little impact on breeding success, although well-fed females were less likely to solicit food from males not their mate or to copulate with outside males.”

Once the female lays her eggs, she usually will do the majority of incubation, although the male may assist to varying degrees, according to the BNA. Incubation usually lasts 37 days.

Incubation has definitely started for the pair I’ve been keeping tabs on. Whenever I visit the location now, one of the birds is hunkered tightly down into the nest. I’m not sure if it’s the male or the female, as there is no obvious difference in plumage color or pattern between sexes. However, according to some bird identification guides, the brown-streaked band of feathers on the lower neck of ospreys is usually heavier and darker in females. This is not always easily visible, though.

Besides this site, there are at least two more nests in the area of which I’m aware. I’ve observed osprey in both of them, so it will be interesting to keep tabs on the families as the season progresses.

Stay tuned for more news from Osprey Central.

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