In the Neotropics, Ospreys breed in coastal northwestern Mexico, in Belize, and in the West Indies. Resident populations in Mexico (P. h. carolinensis) nest along both coasts of central and southern Baja California, along the coasts of Sonora (Russell and Monson 1998, Cartron 2000) and Sinaloa south to Mazatlán (Henny et al. 2008), and along the east coast of Yucatán Peninsula (Quintana Roo) south into southern Belize (Howell and Webb 1995). Also resident (P. h. ridgwayi) in the southern Bahamas (north to Exuma and Cat Island) and Cuba (northern cays, Zapata Swamp; Wiley 1984, Raffaele et al. 1998).
Caribbean (P. h. ridgwayi) and Mexican breeding populations (P. h. carolinensis) are thought to be nonmigratory, but there are few data to back this up, other than sightings of individuals seen in or near nesting areas during the non-breeding season. In Florida (Martell et al. 2004), 7 of 14 breeders tracked by satellite migrated to South America (Brazil, Ecuador, Venezuela), while 6 wintered within Florida, migrating only locally. These findings suggest that long-distance migration among southern populations thought to be resident breeders may be more widespread than previously believed, and that Caribbean and Mexican breeding populations could be at least partially migratory. Study needed.
Why do Ospreys not breed in the tropics ? Along the Caribbean coast of Central America, for example, nesting stops abruptly in southern Belize. Mangrove habitat just south of that (Honduras) is very similar to nesting habitat Ospreys use in Belize, but it is vacant of nests. Similar patterns are found in Europe and Asia -- Ospreys by and large avoid nesting in areas where migrants winter. Because ecology does not seem able to explain this, one begins to suspect competition may play a role, as discussed by Prevost (1982) and Poole (1989). However, there are no data to back this up -- no data showing competition between migrants and residents -- so the mystery remains.
Band returns and satellite data show that most North American migrants avoid wintering in areas where nonmigratory populations breed (Poole and Agler 1987, Martell et al. 2001). Thus 70-80% of the breeders from the eastern and mid-western continental United States and southern and central Canada migrate through the Caribbean to winter in South America, generally north of the equator (see below). Breeders from Washington state, Oregon, and British Columbia winter farther north in Mexico (88%), El Salvador (6%), and Honduras (6%) (25.9°N to 13.0°N and 108.3°W to 87.3°W; Martell et al. 2001).
Recent studies of Ospreys banded along the east coast USA and recovered in Brazil (Mestre and Bierregaard 2009) show key wintering areas in the Brazilian Amazonian states of Amazonas and Pará, near large rivers. The bulk of recoveries were of immatures shot less than one year after banding, with distances from banding and recovery sites between 4191 and 7722 km. Thus it appears that young birds (1st migration/winter) are particularly vulnerable to shooting. Contrasting satellite tracking data with band recoveries shows that the latter produce a biased picture of Osprey distribution in winter, revealing hot-spots of shooting rather than the broader distribution that is typical for this species.
Silva and Olmos (2002) document a concentration of Ospreys wintering in the mangrove estuaries of se. Brazil.
Distribution outside the Americas
Worldwide distribution; nesting across the Palearctic in Scotland, northern Scandinavia, northern Germany, and Poland, across northern Russia and Asia east to Kamchatcka and Japan (Cramp and Simmons 1980). Found from Subarctic south to about 40°N. Most of these birds winter south of 20°N in Africa, India, and southeast Asia. Nonmigratory populations found along coasts of Mediterranean, Red Sea, Persian Gulf, and Cape Verde and Canary Islands (Cramp and Simmons 1980, Poole 1989). Coastal, resident populations found in Australia and islands stretching from New Caledonia to Java.
In North America, breeding habitat varies greatly (boreal forest to temperate coasts/lakes to subtropical coasts to desert salt-flat lagoons), but common denominators are: (1) adequate supply of accessible fish within commuting distance (10–20 km) of nest; shallow waters (0.5–2 m deep), which generally provide most accessible fish; (2) open nest sites free from predators (especially mammalian); such sites generally elevated (e.g., trees, large rocks [especially over water], or bluffs); predator-free islands; and, increasingly, artificial structures such as channel markers, towers supporting electrical lines or cell-phone relays, and platforms built especially for the species.
In coastal Yucatan and Belize, small mangrove (Rhizophora sp.) islands provide key nesting sites, often along coral reefs, with the birds feeding in nearby shallow reef waters. These are potentially productive feeding sites, similar to those found in south Florida (Florida Bay and the Keys).
In Mexico, Ospreys nest on shoreline cliffs and pinnacles surrounded by sparse Sonoran Desert vegetation, dominated by cacti (Judge 1983). Farther south and west in Baja, Ospreys nest on islands in large lagoons 6–12 m deep, surrounded by dunes, natural and artificial brine pans and salt flats, saline marshes, and desert flats (Castellanos and Ortega-Rubio 1995).
Increasingly Mexican breeding Ospreys are finding artificial sites for nesting; e.g., in Scammon’s Lagoon, Baja California, where the population increased from 27 pairs nesting on the ground on small islands in 1946, to 50-86 nesting pairs between 1977 and 1982 when artificial structures (channel markers, power poles, platforms, etc.) became important nesting substrates, and then further increased to 126 in 1993 and 120 in 2004 (including 30 in the town of Guerrero Negro) when artificial nesting structures became even more important (Henny and Anderson 2004). Predators (coyotes, Canis latrans) apparently have driven the shift from ground to structure-nesting.
North American Ospreys spending the boreal winter in the Neotropics inhabit a broad array of ecosystems, from large inland braided rivers to lakes and reservoirs to coastal shores. During winter, 36% of eastern and midwestern ospreys were recovered in South America north of the equator, 24% south of the equator, and 40% in the Caribbean basin, Central America, or the USA (Poole and Agler 1987). Neither age nor breeding latitude influenced the latitude where these birds wintered.
Martell et al. (2001) found that about 65% of 100+ ospreys followed by satellite wintered inland. For banded North American Ospreys recovered in Brazil (Mestre and Bierregaard 2009), > 80% were found in inland waters; most of these were in Amazonian rivers, including the Amazonas (32), Purus (seven), Madeira (five), Japurá (two), Xingu (two), Tocantins (two), Negro (one), Branco (one), Guaporé (one), and Teles-Pires (one) rivers. Other Osprey recoveries near large rivers outside Amazonia were on the São Francisco (two), Paraná (one), and Paraguay (one) rivers.
Silva and Olmos (2002) document a concentration of Ospreys wintering in the mangrove estuaries of southeastern Brazil - part of the major mangrove ecosystem located in the region known as Baixada Santista, covering 120 sq. km. Ospreys fished wide channels bordering these mangrove forests and roosted and did their feeding on bouys and markers in the channels.
Few data from the Neotropics, except for Henny et al. 2008, who provide information from careful surveys in northwest Mexico in 1977, 1992-93, and 2006, showing dynamic changes in local population numbers and some shift in range over this period -- most prominently Scammon's Lagoon (Baja), where a large (100-150 pair) ground-nesting population deserted this lagoon in the early 1990s (apparently in response to predation from coyotes Canis latrans) and settled on artificial structures in nearby towns. This is a dramatic illustration of how adaptable the Osprey is to changes in habitat, and how well it adapts to human landscapes.
Little information on Pandion haliaetus. Two species of Pandion, apparently very similar to modern Osprey but less robust, have been described from the mid to late Miocene. Remains of Osprey are reported from about 12 Pleistocene sites dated to the Pleistocene (2.0–0.1 mya) in western Europe, North America, and in the Bahamas (see Poole et al. 2002).
Poole, A. F. (2009). Osprey (Pandion haliaetus), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.osprey.01