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Osprey

Pandion haliaetus

Listing Status

  • Federal Status: Not Listed
  • FL Status: State Species of Special Concern (only in Monroe County)
  • FNAI Ranks: G5/S3S4 (Globally: Demonstrably Secure/State: Insufficient data for specific rank, but range from Rare to Apparently Secure)
  • IUCN Status: LC (Least Concern)

Appearance:

The osprey is a species of raptor that is sometimes mistaken for the bald eagle.  This species can reach a height of 23 inches (58.4 centimeters) with a wingspan of 72 inches (182.9 centimeters) (The Cornell Lab of Ornithology 2011).   Ospreys have a white underside and head, and a brownish upper body with a black line across the eyes that extends to the wings.  Several features distinguish the osprey from other birds of prey, including a reversible fourth toe and spines located on their feet that are used to help grasp their prey as they fly over the water.

The undersides of the toes on each foot are covered with short spines, which help them grasp slippery fish.

Habitat:

osprey map

The osprey is smaller than the bald eagles that typically share the same habitats, but its five to six foot wingspan is impressive nonetheless. Adults are dark brown above with a white underside and head. Look for the distinctive dark line that extends behind the eye and the gull-like way the narrow wings are angled downward when the birds are in flight.

The osprey is found year-round in Florida both as a nesting species and as a spring and fall migrant passing between more northern areas and Central and South America. Ospreys in Florida did not suffer the serious pesticide-related population declines that occurred in other states in the 1950s and 1960s. Pesticides, shoreline development and declining water quality continue to threaten the abundance and availability of food and nest sites for ospreys.

Osprey habitat includes the coast, lakes, rivers, and swamps in Florida (Florida Natural Areas Inventory 2001).  The osprey is widely distributed in North America and highly migratory at higher latitudes.  Most North American osprey winter in South and Central America, with the exception of the non-migratory, resident subpopulation in coastal southern Florida (Poole et al. 2002, Lott 2006).  The geographic extent of this resident subpopulation is unknown.  Some have suggested that osprey nesting in peninsular Florida south of 29° latitude are non-migratory residents (Poole 1989, Houghton and Rymon 1997).  However, recent satellite telemetry documented that osprey breeding in Lake Istokpoga (Highlands County; approximately 27.25° latitude) routinely migrate to South America (Martell et al. 2004).  In Florida, non-migratory, resident osprey have been well-documented and extensively studied only in Florida Bay, the southern Everglades, and the Florida Keys, which are primarily or entirely within Monroe County (Bass and Kushlan 1982, Kushlan and Bass 1983, Fleming et al. 1989, Poole 1989, Ogden 1996).

Behavior:

Ospreys, also known as "fish hawks," are expert anglers that like to hover above the water, locate their prey and then swoop down for the capture with talons extended.

In Florida, ospreys commonly capture saltwater catfish, mullet, spotted trout, shad, crappie and sunfish from coastal habitats and freshwater lakes and rivers for their diet.

Ospreys build large stick nests located in the tops of large living or dead trees and on manmade structures such as utility poles, channel markers and nest platforms. Ospreys have adapted so well to artificial nest sites that the species now nests in areas (e.g. inner cities) once considered unsuitable. Nests are commonly reused for many years. Nesting begins from December (south Florida) to late February (north Florida). The incubation and nestling period extends into the summer months.

The osprey is listed as a Species of Special Concern only in Monroe County. Permits are required throughout the state to remove a nest for these wonderful raptors, however, and a replacement structure must be erected to mitigate the removal of the nest.

Osprey feed by flying over water and diving feet first to grasp fish with their talons  The osprey’s diet primarily consists of different species of fish including scatfish, mullet, spotted trout, shad, crappie, sunfish, and others.  Feeding areas include most open-water habitats along the coast and freshwater lakes and rivers.

Nesting usually begins in December and lasts until February.  Nests are found in large trees, utility poles, channel markers, and in urbanized areas where ospreys readily utilize man-made nesting platforms.  Like other birds of prey, ospreys will reuse their nests for many years.  In courtship, the male will bring food to the female to keep her from mating with another osprey (Katja Schulz, n.d.).  Females lay two to four yellowish eggs that are incubated for approximately 32 days.  Both adults tend to the eggs and nestlings, though the female does more while the male brings food to the nest.  Young osprey take their first flight around 55 days after hatching, and the adults feed young until they are approximately 100 days old (Ogden 1996).

Threats

osprey

Historically, one of the main threats to ospreys was Organochlorine pesticides (ex. DDT), which were used to control insects.  This chemical caused osprey’s egg shells to soften and prevented the young from developing, which caused a huge decline in the population.  These chemicals are now banned in the U.S., allowing the population to rebound.  One current threat for the osprey is exposure to mercury.  Mercury is found in many waterways which can cause reproductive issues.  Mercury builds up and remains in the food chain, so ospreys are exposed by eating fish which have fed on organisms containing mercury (Lounsbury-Billie et al. 2008).  Another limiting factor is prey availability, which has decreased due to the development of coasts, degraded water quality, and pesticides.

Conservation and Management

The osprey is protected by the U.S. Migratory Bird Treaty Act and as a State Species of Special Concern (in Monroe County only) by Florida’s Endangered and Threatened Species Rule.

Biological Status Review (BSR)
Supplemental Information for the BSR

References

Bass, Jr., O.L., and J.A. Kushlan. 1982. Status of the osprey in Everglades National Park. South  Florida Research Center Report M-679. 28 pp.

Bowman, R., G.V.N. Powell, J.A. Hovis, N.C. Kline and T. Wilmers.  1989.  Variations in reproductive success between subpopulations of the osprey (Pandion haliaetus) in south Florida.  Bulletin of Marine Science 44:  245-250.

Florida Natural Areas Inventory.  2001.  Field guide to the rare animals of Florida. http://www.fnai.org/FieldGuide/pdf/Pandion_haliaetus.PDF

Fleming, D.M., N.C. Kline, W.B. Robertson, Jr. 1989. A comparison of osprey nesting distribution, abundance and success: Florida Bay USA from 1968 – 1984. Bulletin of Marine Science 44: 517.

Houghton, L.M., and L.M. Rymon. 1997. Nesting distribution and population status of U.S. Ospreys 1994. Journal of Raptor Research 31: 44-53.

Katja Schulz.  Editor. "Pandion haliaetus (Linnaeus, 1758)". Encyclopedia of Life, available from "http://www.eol.org/pages/1049145". Accessed 21 Mar 2011.

Kushlan, J.A., and O.L. Bass, Jr.  1983.  Decreases in the southern Florida osprey population, a possible result of food stress.  Pp. 187-200 in Biology and management of bald eagles and osprey (D.M. Bird, Ed.). MacDonald Raptor Research Centre, McGill University,  Raptor Research Foundation, Inc.

Lott, C.A. 2006. A new raptor migration monitoring site in the Florida Keys: counts from 1999 2004. Journal of Raptor Research 40: 200 - 209.

Lounsbury-Billie, M.J., G.M. Rand, Y. Cai, and O.L. Bass.  2008.  Metal concentrations in osprey (Pandion haliaetus) populations in the Florida Bay estuary.  Ecotoxicology 17: 616-622.

Martell, M.S., M.A. McMillian, M.J. Solensky, and B.K. Mealey. 2004. Partial migration and wintering use of Florida by ospreys. Journal of Raptor Research 38: 55-61.

Ogden, J.C., 1996.  Osprey. Pages 170-178 in J.A. Rodgers, Jr., H.W. Kale II, and H.T. Smith (Eds.). Rare and endangered biota of Florida, Vol. V:  Birds. University Press of Florida, Gainesville, FL.

Poole, A.F., R.O. Bierregaard, and M.S. Martell. 2002. Osprey (Pandion haliaetus). The Birds of North America Online (A.F. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online.

Poole, A.F. 1989. Ospreys: a natural and unnatural history. Cambridge University Press, Cambridge, United Kingdom.

The Cornell Lab of Ornithology. (2011). Osprey. Retrieved March 7, 2011, from All About Birds: http://www.allaboutbirds.org/guide/Osprey/lifehistory