The Osprey is 52-60 centimetres (20.5-23.6 in) long with a 152-167 cm (5-5.5 ft) wingspan. It has mainly white underparts and head, apart from a dark mask through the eye, and fairly uniformly brown upperparts. Its short tail and long, narrow wings with four long “finger” feathers (and a shorter fifth) give it a very distinctive appearance.
Juvenile birds are readily identified by the buff fringes to the upperpart plumage, buff tone to the underparts, and streaked crown. By spring, wear on the upperparts makes barring on the underwings and flight feathers a better indicator of young birds. Adult males can be distinguished from females from their slimmer bodies and narrower wings. They also have a weaker or non-existent breast band than the female, and more uniformly pale underwing coverts. It is straightforward to sex a breeding pair, but harder with individual birds.
In flight, Ospreys have arched wings and drooping “hands”, giving them a diagnostic gull-like appearance. The call is a series of sharp whistles, cheep, cheep, or yewk, yewk. Near the nest, a frenzied cheereek! Listen to an Osprey call
The Osprey breeds by freshwater lakes, and sometimes on coastal brackish waters. The nest is a large heap of sticks built in trees, rocky outcrops, utility poles, channel markers, duck blinds, or artificial platforms. Such platforms have become an important tool in reestablishing Ospreys in areas where they had disappeared. Ospreys usually mate for life. The typical lifespan is 20–25 years.
Ospreys usually mate for life. In spring they begin a five-month period of partnership to raise their young. Females lay 3–4 eggs within a month, and rely on the size of the nest to help conserve heat. The eggs are approximately the size of chicken eggs, mottled and cinnamon colored; they are incubated for about 5 weeks to hatching. Incubation by one or both parents works together with the nest structure to provide an ideal environment for the eggs. Bird parents may also wet or shade the eggs to prevent them from overheating.
The newly-hatched down covered chicks weigh only 50–60 g (2 oz), but fledge within eight weeks. When food is scarce, the first chicks to hatch are most likely to survive. The osprey chicks will begin to grow feathers almost immediately, and will be ready to test their wings within 5 to 7 weeks. Chicks are hatched with brownish, reddish, or orange-tinted eyes, which change as they mature to a bright yellow color. After hatching, the chicks become fliers within eight weeks.
Hunting and Feeding
Ospreys are expert hunters, well-adapted to catching live fish. Locating their prey from the air, ospreys will sometimes dive more than 100 feet, pulling up at the last moment before plunging feet-first into the water to capture a fish. Sometimes going completely underwater, the osprey has unique nostrils that close to keep out water. Their heavily muscled legs, powerful wings, and strong feet allow them to catch and fly off with fish up to three feet below the surface of the water! As the osprey rises in flight, it will grasp the fish firmly with two claws facing forward and two facing back. Adult ospreys are capable of carrying fish that equal their own size.
North American Ospreys are migratory raptors, which spend winter in South America and return to the same nesting sites for their spring courtship. While migrating, ospreys will usually travel during the daytime, only occasionally traveling by night.