Sunday, October 10, 2010

Osprey, one of nature's most impressive birds, returns

An adult osprey needs to catch and eat one to three fish everyday - more if it is supporting a family

Simply Living
(First appeared October 11, 2010)

The osprey is back! On the first cool day in October, after being absent during the hot summer months, a solitary osprey has returned to our lake. How consistent this bird has been. Ever since 2008, it has been a seasonal fixture, roosting on a mid-lake platform from October through May.

The white-chested fish hawk arrives before dusk to spend the night perched on a raised 3-foot-square platform in the middle of our lake. In the morning, shortly after dawn, the osprey flies away. I don't know if the 2-foot tall bird with the 4- to 6-foot wingspan goes far away or stays nearby because sometimes I see it during daylight hours sitting in one of the tall pine trees that grow along the shoreline or circling overhead in search of a meal.

Ever since Ralph built the platform and erected it in the middle of the lake, I've been hoping an osprey would nest there. Ospreys become sexually mature when they are 3 years old, which means if this bird arrived as a juvenile in 2008, 2010 might just be the year it is ready to mate. I'd be so excited if that happened.

Female ospreys tend to arrive about 10 days after the males. So far, I've only observed one bird, which I believe is a male. Although they look very similar, females are slightly larger than males and sport a "necklace" of mottled brown chest feathers. Once the female arrives, the male courts her with an aerial ballet. To impress his potential partner, the high-flying raptor performs a sky dance while carrying either a fish or nesting materials in his talons. If the female is sufficiently impressed by this winged display, the pair will mate and begin the process of nest building.

Nests are built atop tall trees or manmade platforms like the one in our lake. Usually, the birds choose a location close to water, where food is plentiful and the sharp-eyed raptors can survey their surroundings. As monogamous animals, once they've mated, ospreys stay together for life. They also return to the same nest year after year. It would fulfill one of my dreams if the nesting platform in our lake became the permanent home to a pair of ospreys.

Unlike eagles or hawks — whose diets include small animals as well as fish — ospreys dine almost entirely on live fish. An adult bird needs to catch and eat one to three fish every day to supply its own dietary needs, but that number increases dramatically once baby birds are born. Female ospreys lay an average of three eggs that both parents take turns incubating for the five- to six-week gestation period. How many of those hatchlings survive depends on the availability of food. An osprey family needs to consume six to eight fish a day. If fish are plentiful, survival rates will be high. If there are not enough fish, the last baby birds to hatch will be the least likely to live.

I don't know if our lake will support a family of ospreys or if the platform in the middle of the lake will work for anything other than a nighttime perch, but I hope in the weeks ahead to find out. In the wild, an osprey's lifespan is 13 to 16 years. This autumn marks the third year "my" osprey has been visiting our lake. Even if the solitary raptor doesn't decide to make a nest, I can at least look forward to many more years of seasonal visits by one of nature's most impressive birds.

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