Osprey

If you’ve looked up as you’ve driven past Marvin Park in Salida lately, you may have noticed some new residents. In April, a pair of Osprey—North America’s premier fish-eating raptor—started building a nest on a field light west of the bleachers in Marvin Park. Following the Arkansas River upstream to this great spot, these pioneers may have moved up from Pueblo Reservoir, where a pair first nested in 1990.

Larger than a Red-tailed Hawk but smaller than a Bald or Golden Eagle, an Osprey appears all dark brown above except for a white cap; it appears bright white below although some birds show a spotted “necklace.” A dark mask extends from the strongly hooked bill to the nape of the neck, encompassing a bright yellow eye. Ospreys occur on all continents around the world except Antarctica. The Osprey is the continent’s only raptor that eats almost exclusively live fish. Despite this restriction, though, Ospreys have colonized a broad array of habitats; beyond the varying particulars, nests generally are located no further than 15 miles from shallow waters teeming with fish.

Looking for just about any plentiful species of fish that’s 4 – 12 inches long, an Osprey dives feet first after prey, accessing only about the top 3 feet of water. Sometimes, the raptor finds itself actually in the water and has to use its long, strong wings to pull itself and its meal out. If successful, the airborne bird positions the fish headfirst—creating a more aerodynamic flight—and carries it to an elevated perch. When perching, an Osprey’s foot has 3 toes pointing forward and 1 pointing back. But because the outer toe on each foot can reverse, the bird can carry slippery fish more efficiently by clasping with two toes in front and two in back.

In Colorado, males generally arrive on their breeding grounds a few days before females. Birds return to the same nest or territory each year, sometimes for decades. Pairs with established and still-intact nests can start laying eggs as quickly as 7 days after arrival, with only minimal time devoted to nest-refurbishment. If building a new nest, though, pairs can work for 20 days or more before laying.   In many areas, artificial nesting platforms on tall poles have helped breeders enormously. Historically Ospreys built their nests atop trees or rocky cliffs. Today many have shifted to artificial sites such as the Marvin Park light pole or hundreds of these artificial nesting platforms. Ospreys nest in single pairs or in loose colonies but only rarely expand to new locations, which makes the Salida breeding pair even more special. Both parents incubate the clutch—typically 3 eggs—although the female shoulders the bulk of this task. Hatching occurs about 38 days after laying. The female remains with the young most of the time during the first month, sheltering them from sun and rain, while the male brings fish for the female to feed to the young. After the first month, the female joins in the fishing tasks to feed the growing kids. Around 50 days after hatching, the youngsters begin to venture from the nest, sometimes returning at night and for resting. The adults help the fledglings for another 10 – 20 days while they hone their fishing skills. The family unit breaks up and the birds begin to migrate shortly after that, typically in August or September, to winter along the coasts, fish-rich lakes, and rain-forest rivers of Central and South America.

The Osprey’s scientific name (Pandion haliaetus) has a rather convoluted and confusing origin that lies in a myth about a mythological king of Athens (Pandion). In this long story of revenge, angry gods, and humans turned into birds, Pandion really had nothing to do with much of anything in the story. Carl Linnaeus, who provided the scientific name, either had never read the myth or completely misunderstood it. The species name has slightly clearer roots: Haliaetus derives from Latin “haliaetos,” the name of a sea eagle. Even the common name of Osprey has a strange origin. From Latin “ossifragus,” meaning “bone” (”os”) and “to break” (“frangere”), this term actually refers to the lammergeier, a vulture of Europe, Asia, and Africa that drops bones and turtles from the air to break them up. Who knows quite why, but this name was transferred to the Osprey in the 16^th century. Go figure.

In the 1960s, Ospreys disappeared from most of Colorado due to the pesticide DDT and other pesticide-related problems. One small remnant population survived around a few lakes in Jackson County, in the North Park area of northern Colorado. Following one reintroduction effort by Colorado Division of Wildlife (now Parks and Wildlife) and the population expansion that accompanied the ban on DDT, local populations in Colorado have become established around lakes and rivers once again.

So next time you’re in Salida, check out the light poles west of the ball fields in Marvin Park. Above the jumble of sticks on the light, you’ll likely see a head with a dark mask. And soon, you’ll start seeing the nestlings themselves. With the river, Frantz Lake, and Sand Lake all just a few wingbeats away, what could be better to raise a next generation of little fish-eaters?

You can learn more about and see photos of Ospreys here.