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Osprey

Pandion haliaetus

Order:
Accipitriformes
Family:
Pandionidae
Sections

Systematics

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Geographic Variation

Sexual differences in plumage and size confuse the issue of geographic variation: within populations, females average 15–20% larger in body mass than males and 5–10% longer in wing, tail, claw, and bill (see Appearance: Measurements). In addition, females tend to have the head darker and the breast-band fuller and darker, although each trait varies among populations (see below).

The Osprey shows geographic variation in plumage and size, but only moderately so given its worldwide distribution (Prevost 1983a, Poole 1989a). This pattern contrasts sharply with that in the more sedentary (i.e., less migratory) Haliaeetus eagles, which have differentiated greatly, with eight distinct species over a range nearly identical to that of the Osprey.

Body size in the Osprey adheres to Bergmann’s rule, with birds from tropical and subtropical climates being smaller than those at cooler, higher latitudes; e.g., sex-for-sex, the wings of Australasian individuals average 12–14% shorter than individuals in the Palearctic, and breeders in the Caribbean average slightly smaller than breeders in the U.S. (Prevost 1983a). Plumage coloration tends to follow Gloger’s rule, with breeders at warmer, drier subtropical latitudes—such as those in Baja California or around Caribbean Sea—being paler than breeders at cooler, wetter, and higher latitudes (Prevost 1983a).

Taking a worldwide view, the combination of a dark breast-band and pale head sets apart breeders in Australasia from other populations. There, the male has the crown slightly darker than the female’s. Palearctic and Nearctic breeders are most similar and can be confused easily, although the former (except in southern populations) have the breast-band slightly darker and the underwing coverts darker and more heavily barred.

Geographic variation among North American populations is slight. Relative to their counterparts farther north, Caribbean breeders have the crown and breast noticeably paler—they appear almost white-headed and white-breasted, with little difference between the sexes (females average slightly darker, but not enough to be distinguished reliably; Blanco and Rodriguez-Estrella 1999). Paler individuals such as these breed occasionally in southern Florida, but even there most breeders are darker like those farther north. Still, these observations suggest, perhaps not surprisingly, at least some interchange between Caribbean and U.S. populations. And recent evidence hints at darker individuals (P. h. carolinensis) breeding in Cuba, although more work is needed to confirm this (Wiley et al. 2014).

In Baja California, residents are pale and thus resemble Caribbean birds, with the breasts, crowns, and underwing coverts almost immaculate white, although the crown is darker (Prevost 1983a, Blanco and Rodriguez-Estrella 1999).

Subspecies

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Subspecies P. h. carolinensis breeds in North America north of the Caribbean and overwinters south to southern South America. The largest subspecies, on average. Underwing coverts of primaries barred dark brown on inner web and wholly dark brown on outer web; head white with black mask; breast markings moderately developed on female and often lacking on male.

© Brian Sullivan, California, United States, 6 March 2011
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Subspecies P. h. carolinensis.

© Brian Sullivan, New Jersey, United States, 5 May 2009

Four subspecies, following Prevost 1983a (as modified in Marchant and Higgins 1993 and Dickinson and Remsen 2013; see also Stresemann and Amadon 1979, and Henny 1988b), diagnosed on color and pattern of birds in Definitive Basic Plumage and to a lesser extent on body size. A recent taxonomic review (Monti et al. 2015), based on an extensive study of mitochondrial DNA, found four main genetic groups representing quasi non-overlapping geographical regions (Americas, Indo-Australasia, Europe-Africa and Asia). By this analysis, the Americas may hold only one Osprey subspecies, but Caribbean data were few in this work, so we await further study before combining the two currently recognized American subspecies.

P. h. carolinensis Gmelin 1789. Includes P. h. cayennensis Gmelin 1789. Breeds in North America north of the Caribbean (see Distribution) [type locality = South Carolina]; winters south to South America and has occurred as a vagrant to Iceland and the Azores (Strandberg 2013). Underwing coverts of primaries barred dark brown on inner web and wholly dark brown on outer web; head white with black mask; breast markings moderately developed on female and usually lacking on male; large (the largest subspecies, on average).

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Subspecies P. h. ridgwayi is resident in the Caribbean from the Bahamas and Cuba south to the coast of southeastern Mexico and Belize. Birds that appear to be this subspecies, as well as intermediates, occur sparsely in south Florida. Note head largely white (dark markings reduced on crown and mask), underwing coverts of primaries mostly white; breast markings reduced or lacking in both sexes.

© Harold Brewer, North Andros, Bahamas, 12 May 2014
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Caribbean subspecies P. h. ridgwayi.

© Jesús Bobadilla Aguiñaga, Yucatán, Mexico, 15 January 2016
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Caribbean subspecies P. h. ridgwayi.

© Linda Barry-Cooper, Freeport and West Grand Bahama, Bahamas, 30 September 2015
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Caribbean subspecies P. h. ridgwayi.

© Dan Belcher, Turks and Caicos Islands, Turks and Caicos Islands, 13 March 2016

P. h. ridgwayi Maynard 1887. Resident in the Caribbean from the Bahamas and Cuba south to the coast of southeastern Mexico and Belize; not currently found breeding south of southern Belize and Cuba [type locality = Andros Island, Bahamas]. Like P. h. carolinensis, but underwing coverts of primaries mostly white (pale brown is restricted to the distal two-thirds of outer web), head largely white (dark markings reduced on crown and mask), and breast markings reduced or lacking in both sexes; averages somewhat smaller, but overlap is extensive. Also, the dorsum may average paler brown, perhaps an effect of bleaching by the sun.

P. h. haliaetus Linnaeus 1758. Includes P. h. friedmanni Wolfe 1946, and P. h. mutuus Kipp 1951 (see Prevost 1982). Breeds in the Palearctic from Europe and the northwest coast of Africa east through Asia, north of the Himalayas [type locality = Sweden]; overwinters in southern Africa, India, and East Indies. Like P. h. carolinensis, but underwing coverts of primaries unbarred white on inner web and wholly rufous brown on outer web, crown blacker, and breast markings more strongly developed sex for sex (Strandberg 2013). Southern populations, such as around the Mediterranean Sea and Red Sea, are paler and whiter, especially on the underwing coverts.

P. h. cristatus Vieillot, 1816. Includes P. h. leucocephalus Gould 1838 (fide Dickinson and Remsen 2013); P. gouldii Kaup 1847; P. h. australis Burmeister  1850; P. h. minor Schleg 1869; P. h. melvillensis Mathews 1912; and P. h. microhaiaetus Brasil 1916. Resident in Australia and the Southwest Pacific from Guinea west to Celebes and perhaps Java, east and south to New Caledonia and Vanuatu (for details see  Poole 1989a and Marchant and Higgins 1993; type locality = New South Wales, fide Condon 1975). Similar to P. h. haliaetus, but underwing coverts of primaries unbarred and extensively ashy brown, head largely white, with male significantly darker than female, and breast markings moderately well developed; small (the smallest subspecies, on average), with body size increasing from north to south.

Related Species

Placement of the monotypic genus Pandion within the Accipitriformes—the avian order that consists of the kites, hawks and eagles—was in flux for decades. For example, an analysis of egg-white proteins placed Pandion in its own family (Sibley and Ahlquist 1972), yet cytochrome b sequence, part of the mitochondrial DNA (mtDNA) strand, placed it within Accipitridae but diverged enough to warrant classification in separate subfamily, Pandioninae, with divergence estimated to have occurred 24–30 mya (Seibold and Helbig 1995b). Analysis of variation in syringeal morphology suggested that Pandion grouped closely with the Accipitridae sensu stricto as well as with the Sagittariidae, a monotypic family that includes only Sagittarius serpentarius, the Secretarybird of Africa (Griffiths 1994a). More extensive phylogenetic analyses, with sampling across a suite of genes, has tended to support placement of Pandion in its own monotypic family (Lerner and Mindell 2005, Lerner et al. 2008b). Hybrids involving this species are unknown.

Species limits within Pandion have been debated in the past decade. An analysis of mtDNA sequence revealed deep divergence times among populations in the Nearctic, Palearctic, and Australasia (Wink et al. 2004b). On the basis of this time difference, coupled with morphological differences—which, of course, are necessary to define a subspecies—some have argued that there are up to four species of Ospreys, two if only P. h. cristatus, the Eastern Osprey, is split (Christidis and Boles 2008) and as many as four if each subspecies is treated as a species (Wink et al. 2004b). Neither the American Ornithologists’ Union nor BirdLife International recognizes a species level split in Pandion.

Recommended Citation

Bierregaard, Richard O., Alan F. Poole, Mark S. Martell, Peter Pyle and Michael A. Patten.(2016).Osprey (Pandion haliaetus), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/osprey

DOI: 10.2173/bna.683