Osprey

Osprey

Text and photos © Dan Gleason

The Osprey may be one of the most recognized raptors in the Pacific Northwest, identified even by non-birders with its white underparts and loud chirping. It has sometimes been called “Fish Hawk,” a reference to its preferred food. Osprey are exclusively fish-eaters and almost never eat anything else. This dependance on fish is why Osprey only nest and feed along rivers, streams, lakes and large ponds, or in bays, estuaries or in shallow water just offshore along the coast.

Osprey can sometimes be seen hovering, strongly flapping its wings while maintaining a stationary position high over the water. From this vantage point, it can clearly see fish in the water below. When likely prey is spotted, the Osprey plunges downward. Before striking the water, it thrusts its feet forward, entering feet first, talons spread to catch the fish. As it seizes its prey, the long, curved talons pierce the fish as the strong foot closes. The underside of the Osprey’s foot has many small, sharp scales, acting like spines to help firmly grip slippery fish. Large, powerful wings enable the Osprey to lift itself out of the water, despite the weight of the fish. As the Osprey gains altitude, you may see it shake, throwing water off the feathers. Then it turns the fish so that it points head-first into the airstream. This position offers less air resistance, allowing the bird to fly easier until it reaches a feeding perch.

An Osprey never dives deep, taking fish near the surface, usually within 12–30 inches of the surface. Carp and other fish not sought by sport fishermen are frequently taken but a trout near the surface will certainly not be ignored if it can be caught. Adults usually hunt some distance away from the nest where the young may not see the process, but, since young Osprey will hunt eventually use the same technique, we believe this method of fish capture is innate. Once out of the nest, the fledglings still depend upon their parents to bring them fish, but, the young soon begin attempting to capture fish in the same manner as the adults. Usually, this happens about 10-12 days after the young leave the nest, but some try fishing attempts as early as 5-7 days post-fledging. By 20 days, the young birds have all learned to catch their own food. This is good, because the adults will soon head south for the winter, leaving the young to fend for themselves until they migrate a few days later.

In winter, Osprey leave much of North America, except for parts of the south, especially Florida, where many Osprey are resident and do not migrate. Most of Oregon’s Osprey winter along coastal waters of southern Mexico but some may go as far as Honduras. In recent years, a few individuals may be found in our area in winter, but it is not clear where these birds are from or why they have not migrated further south. However, they survive just fine as long as some open water remains available for fishing.

Osprey form monogamous pairs and are generally life-long mates. However, male and female of a pair do not winter together. In fall, females may leave as much as 20 days before their mates, and the males will likely not be found in the same locale as their mates during winter. When the birds return north in spring, males usually arrive 4-7 days before females, and during the days before their mates arrive, they begin nest repairs or construction. If the pair already has an existing nest, the female may lay eggs within a week of her arrival. If a new nest needs to be built, or extensive repairs to an old nest are needed, it can take 10-20 days for egg-laying to begin.

Osprey like to nest as high as possible in a visible spot, unlike Bald Eagles who prefer to nest well-hidden in the canopy of large trees. Osprey nests are easy to find and I am sure you have probably seen their very large collections of sticks atop an old snag or light pole. Much to the displeasure of utility companies, they also love to nest atop utility poles near water. A good solution to this problem is to place a platform atop a new pole that is taller than anything else in the area. Osprey will readily accept a provided platform as long as it is the tallest structure in the immediate area. A very high and exposed nest makes it safe from most predators, although Bald Eagles and Great Horned Owls will still sometimes take young Osprey.

Osprey are very faithful to their nest site. Nests are typically reused year after year by breeding pairs and if the pair disappears, another pair may take over the nest, repairing and reusing it in subsequent years. Osprey are usually at least three years old before they are ready to breed and some don’t breed until they are five to seven years old. When ready to breed, young males often return within 10 miles of their hatch site and females are usually found within 25 miles of theirs.

Pesticides, especially DDT and its derivatives, decimated Osprey populations in the 1950s-1970s. These chemicals became concentrated in the food chain, causing egg shell thinning, poor hatching success and high mortality rates in adults. Thankfully, Osprey made a strong return after use of these pesticides was banned. Osprey are common along waterways throughout western Oregon, even in urban locales with high human activity. They are impressive birds with dramatic behaviors that capture the attention of even those people who do not have a strong interest in birds.

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