Studies reveal winter habitat choices, migration routes of Osprey

Osprey experts writing in the Journal of Raptor Research have revealed details of the bird’s winter habitat, described new winter grounds in Argentina, and shed light on the fish hawk’s return flights.

From 1995 to 2009, researchers led by Brian Washburn of the National Wildlife Research Center in Ohio tracked 79 adult birds by satellite to their wintering areas in the Caribbean, Central America, and South America. Previous recoveries of banded birds had revealed the general range, but GPS-enabled tracking devices gave the team new insights.

About half of the raptors wintered on rivers, 30 percent stayed near coasts, and approximately 20 percent preferred lakes. Females stayed in their wintering areas for about two weeks longer than males. Individual Osprey returned to the same area each year.

The species is common in winter from the coasts of Colombia to eastern Brazil, but in the last 20 years, it has been found in greater numbers much farther south — in northern and central Argentina, where it is now reported year-round. Reservoirs and lakes that stock native and exotic fish “may have provided a new habitat and feeding opportunity” for the birds, reports author Miguel Saggese.

The first in-depth study of spring migration, conducted from 1996 to 2013 by Mark Martell of Audubon Minnesota and six other scientists, found that the majority of East Coast-nesting Osprey wintered in South America and crossed the Caribbean Sea to Haiti, Jamaica, or Cuba in flights lasting 27-40 hours. Then the birds continued north through Cuba and Florida and up the coast as far north as Maine.

Martell also learned that most Osprey wintering in Mexico and Central America flew north through valleys west of the Rocky Mountains and followed similar routes south in fall.

A version of this article appeared in the April 2015 issue of BirdWatching. Subscribe.

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Originally Published March 13, 2015