Pandion haliaetus

Ospreys have long narrow wings, dark brown upperparts, white underparts, a white head with a prominent dark eye streak, and dark wrist patches (visible in flight) on the underside of the wings. Immatures have pale buff edging on the dark feathers of the upper surface. Females are more likely than males to have a necklace of dark streaking. Average length 56-64 cm, wingspan 147-183 cm.

Differs from other hawks in having all of the following characteristics: white belly, dark wrist patches, and a white head with a prominent dark eye streak. Other hawks do not habitually plunge feet-first into water to obtain prey.

Ospreys occur primarily along rivers, lakes, reservoirs, and seacoasts. They often cross land between bodies of water. They typically build large stick nests on living or dead trees and also use numerous man-made structures such as utility poles, wharf pilings, windmills, microwave towers, chimneys, and channel markers (Henny, in Palmer 1988, Campbell et al. 1990). Nests are usually near or above water.

Raccoons can be a major source of nesting failure in some areas.

Nesting phenology varies throughout the range. For example, in Florida, eggs are laid from late November to early March, with a peak from December to mid-January. In the Chesapeake Bay region, ospreys first arrive at nests early to mid-March, lay eggs from late March to mid-May, with a peak in April. In southern New England, ospreys arrive beginning in mid- to late March, and eggs are laid between early April to early June, with a peak in mid- to late April. In east-central Labrador, ospreys arrive around early May, and eggs are laid from mid-May to mid-June.In southeastern British Columbia, ospreys arrive in mid- to late April, with egg laying from early May (peak) to late May.

Clutch size is 1-4 (most often 3). Incubation, usually mainly by the female (male provides food), lasts 5-6 weeks. Young fledge in around 50-60 days and thereafter are dependent on their parents for up to several additional weeks. Individuals first breed usually at 3 years, sometimes at 4-5 years.

Delays in clutch initiation, such as caused when Canada geese occupy nest sites, may cause a reduction in reproductive output (Steeger and Ydenberg, 1993, Can. J. Zool. 71:2141-2146). Number of young fledged increases with increased abundance of food resources. Large numbers may nest in a relatively small area when food resources are adequate and nesting sites are plentiful.