San Diego Management & Monitoring Program


Osprey
Pandion haliaetus


Kingdom Phylum Subphylum Class Order Suborder Family

Current distribution rangewide

Worldwide distribution; In the United States breeding populations occur along the Pacific Coast, in the Western Interior, the Great Lakes, the Atlantic Coast , Alaska, Florida, and the Gulf Coast. Winters from southern North America south to Central America and South America [1]. Pacific Coast populations extend from Washington to southern California, including the Channel Islands.


Known Populations in San Diego County

Occurs in MUs 1, 2, 3, 4, 6, and 7 in the MSPA, with most known localities along the coast and in the coastal lowland [2]. Also found further inland at Lakes Cuyamaca, Barrett, and Moreno.


List status

Not listed


Habitat affinities

Exposed locations are needed for construction of their large nests. Often found on pillars of rock in the surf, on over-hanging ledges close above the water, and tops of older trees or artificial substrates that are located within 500 meters of open water [3]. Known to nest in a diversity of habitats as long as fishable waters are accessible [4].


Taxonomy and genetics

Four recognized subspecies differentiated by geographic distribution, size and coloration. Only one subspecies, Pandion haliateus carolinensis is found in North America [5].


Seasonal activity

Yearlong, diurnal activity. Nesting season begins mid-March to early April. Fall migration begins in October heading south along coast and western slope of Sierra Nevada to Central and South America. In the winter the osprey occurs more frequently than in breeding season [6].


Life history/ reproduction

Breeds March to September. Clutch size 1-4 eggs, usually 3. Colonial nesting is common. Young breed first at 3 yr. Pesticides caused reproductive failure in past, but reproductive success has increased since the banning of nondegradable organochlorine pesticides in the early 1970's [7, 8].


Diet and foraging

Primarily consumes fish; forages over fishable waters diving up to a meter in depth for prey [9]. Occasionally takes small mammals, birds, reptiles, amphibians, and invertebrates.


Dispersal

Home ranges vary with season and quality of habitat; during breeding season travels up to 8-10 km from nests to forage for fish, mainly near the coast [10].


Threats

Threatened by exposure to mercury and other contaminants in the food chain. Vulnerable to power line and pole electrocutions, direct mortality with wind turbines, collisions with vehicles, overfishing, and urbanization [11, 12, 13].


Special considerations:

Populations in North America have stabilized or increased with the restriction or banning of certain pesticides. Use of poles that support electrical lines have posed risks of electrocution, power outages, and fires. Recommendations to modify these nest that occur on poles has been accomplished in many countries. Ospreys are surprisingly tolerant of human activity and nest in urban and suburban habitats. Habituation is imperative for this species and pairs that are not used to human activity may abandon nests if disturbance is sudden or for extended duration [14].


Osprey sources