18 Frequently Asked Questions About Ospreys

Frequently Asked Questions About Ospreys

Frequently Asked Questions About Ospreys

Ospreys, scientifically known as Pandion haliaetus, are one of the most popular birds in North America. Associated with shorelines and various bodies of water, ospreys’ large nests can be observed readily from afar.

Ospreys are also known as Fishhawks. As the name suggests, ospreys feed almost exclusively on fish, and although they are incapable of swimming, they dive into the water to catch fish from heights of up to 90 feet.

Nesting in North America, ospreys spend the winter in the southern United States, Central, and South America. The population of ospreys dropped drastically from the early 1950s to the 1970s. After the banning of DDT in 1972, osprey populations rebounded.

1. Where do Osprey nest?

Where do Osprey nest
Typical Osprey nesting habitat. Photo: Stan Hope/Flickr/CC by-SA 2.0.

Ospreys nest in a wide variety of habitat types. Good nesting sites are emerging dead or live trees or other structures with easy access located near rivers, lakes, bays, reservoirs, lagoons, swamps, and marshes. Some ospreys have nested within 10 miles of a body of water.

Areas near water have become prime real estate reducing the number of available nesting sites. Ospreys now nest on channel markers, communication towers, utility poles. Many people provide nesting platforms, which birds readily take.

Nesting Ospreys defend only the immediate area around their nest rather than a larger territory. They will chase away other Ospreys that encroach on their nesting areas.

osprey adaptations
An osprey performing the sky-dance.

The Osprey nests mostly in northern North America, along the coasts of New England, Florida, and other regions (see the breeding range map below). A nearby source of food is the only requirement.

At the beginning of the breeding season, males perform an aerial “sky-dance,” sometimes called “fish-flight.” With dangling legs, often clasping a fish or nesting material in his talons, the male alternates periods of hovering with slow, shallow swoops as high as 600 feet or more above the nest site.  The male makes repeated screaming calls while gradually descending in an undulating fashion to the nest.


 2. What does an Osprey Nest look like?

osprey nest
Osprey nests grow in
depth as they are reused every year. Photo: MK Campbell/Flickr/CC by-SA 2.0. 

An Osprey nest is an untidy platform made of sticks with a central depression lined with smaller sticks, vines, and algae. The same nest is reused every year and additional material is added resulting in huge nests of up to 11 feet deep and 5 feet in diameter.

The male finds the nesting site and collects most of the nesting material by fly-by-plucking thin branches of trees. The female sits on the nest, arranging the nesting material.

Artificial platforms are becoming a common nesting site as prime Osprey nesting sites are converted to urban development.


 3. How many eggs do Ospreys lay?

Ospreys lay from 1 to 4 eggs per clutch. First time nesting pairs tend to lay two eggs only, and most experienced pairs lay three eggs. Some pairs lay up to 4 eggs.

4. What do Osprey eggs look like?

osprey eggs
Osprey eggs. Photo: Chesapeake Bay Program/Flickr/CC by-SA 2.0.

Osprey eggs are cream to pinkish cinnamon spotted and blotched with reddish-brown.

The female osprey lays one egg every other day after she starts laying eggs.

The time she takes to complete a clutch depends on the number of eggs she lays, and a 4-egg clutch typically takes between 8 to 10 days to complete.

5. How long do Osprey chicks stay in the nest?

Parent Osprey and 5-6 week-old chicks. Photo: Fishhawk/Flickr/CC by-SA 2.0. 

After hatching, Osprey chicks stay in the nest for 50-55 days before leaving the nest. At hatching, chicks are capable of limited motion, are covered with down, and have their eyes open.

The young remain with their parents for up to two months after they fledge. Young ospreys migrate to the wintering grounds after splitting from their parents and stay there for two to three years until they come back north to breed.

6. How long does it take for an osprey egg to hatch?

An Osprey egg hatches in 36-42 days. Both parents take turns incubating the eggs.

7. How can you tell the difference between a male and female osprey?

osprey nest and parents
Male and female Ospreys. Females are larger, but size differences can be difficult to tell in the field. Photo: Henry T. McLin/Flickr/CC by-SA 2.0.

Female Ospreys are larger than males. 

Females average 15–20% larger body mass than males and 5–10% longer in the wing, tail, claw, and bill.

In addition, females tend to have the head darker and the breast-band fuller and darker, although each trait varies among populations.

Sexual differences in plumage and size vary among populations in different regions.

8. Is an Osprey the same as a Seahawk or Fishhawk?

Yes, an Osprey is also known as Fishwawk, Seahawk, or Riverhawk.

9. Is an Osprey a Hawk or an Eagle?

Ospreys are closely related to hawks and eagles (Family Accipitridae), but genetic analysis shows that Ospreys diverged enough to warrant classification in a separate subfamily, Pandioninae.


10. Are Ospreys endangered?

The excessive use of DDT was the main cause of the osprey population decline.

Ospreys are no longer endangered under the Endangered Species Act. Ospreys are still listed as threatened in some states, particularly inland states, where the excessive use of pesticides extirpated many populations.

Ospreys have a fascinating conservation story. Most North American populations experienced a drastic population decline in the early 1950s to 1970s. The cause of this decline was attributed to the use of pesticides, mainly DDT, which poisoned the birds, thinned their eggshells, and made nests fail.

The Pesticide DDT was banned in 1972 and marked the beginning of the Osprey population rebound. The widespread construction of artificial platform nests also had a positive impact on the growing populations.

According to the North American Breeding Bird Survey, ospreys populations grew by 2.5% per year from 1966 to 2015.

11. Are ospreys protected by law?

Yes, Ospreys are Federally protected under the Migratory Bird Treaty Act (MBTA). Each estate has laws that protect Ospreys to various degrees.

The MBTA states that: It is illegal for anyone to take, possess, import, export, transport, sell, purchase, barter, or offer for sale, purchase, or barter, any migratory bird, or the parts, nests, or eggs of such a bird except under the terms of a valid permit issued pursuant to Federal regulations.

The migratory bird species protected by the Act are listed in 50 CFR 10.13. View more information and the list at Migratory Bird Treaty Act.

12. How many ospreys are in North America?

Partners in Flight estimates a global breeding population of 500,000 birds in North America, with 21% spending some part of the year in the U.S., 28% in Canada, and 3% in Mexico.


13. What Do Ospreys Eat?

Ospreys hover and dive into the water to catch fish.

Ospreys feed nearly exclusively on live fish. On very rare occasions, they have been spotted eating dead fish and snakes.

Ospreys glide or soar with shallow wing beats over the water. The bird scans the surface for fish located within 2 feet or less from the surface.

Upon spotting a fish, an osprey plunges into the water with its feet first from heights up to 70 feet. The bird then carries the fish in its talons to a favorite perch, where it proceeds to eat it.

Ospreys are solitary birds; they live alone for most of the year except during the breeding season when they form breeding pairs. Small flocks of 5-10 birds have been seen roosting together.

14. Can Ospreys swim?

Ospreys are unable to swim but soar over the water to catch a fish. They plunge feet-first 1 to 2 feet into the water. Once an Osprey catches a fish, the bird will orient the fish head-first to minimize the wind resistance.

15. What type of special adaptations do Ospreys have?

osprey diving

Ospreys have key adaptations for fishing. They have long, sharp, and hooked claws to grip slippery fish. Their feet have gripping pads to help them hold and handle the fish they catch.

Ospreys have long and narrow wings that enable them to perform slow-soaring over water for long periods.



16. What are the threats to Ospreys?

Osprey’s traditional nesting sites, which are located near bodies of water, have become prime real estate and are being replaced by urban development. The loss of nesting habitats forces ospreys to find nesting sites further from their fishing grounds.

Fish farms and fish ponds often attract Ospreys. Ospreys find abundant fish easy to catch and will return every day. Farmers often shoot Ospresy as a mean to stop losing their fish.

Ospreys are occasionally shot in the breeding grounds.

Ospreys are shot in countries where they spend the winter. Their slow soaring and tendency to perch in exposed perches makes them an easy target to recreational hunters.

Entanglement with baling twine and other discarded lines is also a source of the death of Ospreys. Nesting birds bring these items onto their nest, which end up wrapped around adults and chicks.

17. Where do Ospreys go in the winter?

Map showing the Osprey breeding and wintering grounds.

Ospreys breed in North America during the summer months and migrate to Southern United States, Central and South America to spend the winter months.

Ospreys that nest in eastern North America migrate south along the eastern region through Florida and then Cuba and Hispaniola. Some birds winter in the Caribbean Basin, and many continue to Central and South America.

Ospreys that breed in the Western region of North America don’t migrate as far, and winter in Central America.

Ospreys nesting in central Québec in Canada overwinter in southern Brazil. These birds fly more than 200,000 kilometers back and forth during their 15 to 20-year lifetime.

18. What type of calls do Ospreys make?

Ospreys make distinctive calls. The video shows the most common calls of an Osprey.

References:

  • Alerstam, T.; Hake, M.; Kjellén, N. (2006). “Temporal and spatial patterns of repeated migratory journeys by ospreys”. Animal Behaviour. 71 (3): 555–566.
  • Bierregaard, R. O., A. F. Poole, M. S. Martell, P. Pyle, and M. A. Patten (2016). Osprey (Pandion haliaetus), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.
  • BirdLife International (2013). “Pandion haliaetus”. IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature.
  • All About Birds. Cornell Laboratory of Ornithology. https://www.allaboutbirds.org/