Osprey migration usually begins early, with most birds leaving northern locations by the end of August. Because of their dependence on fish as their source of food, Ospreys from the interior of North America must migrate to areas where the lakes and rivers don't ice up. Ospreys that breed in the United States travel as far as southern South America. The bulk of the passage is completed by the first week of October, even at the watch sites along the Texas coast and Florida Keys.
After hatching, young birds leave the area of their birth and travel south to wintering locations where they stay for the next year, not returning to breeding areas until they're two. It's difficult to characterize the life-history patterns of American Ospreys because the species is still in the process of recovery from near extinction as a result of pesticide use in the mid 1900s. We may ultimately discover that coastal populations have unique patterns of migration and dispersal by juveniles. Because Ospreys spend so much time in South America, they're particularly susceptible to the effects of habitat degradation caused by humans, which increases the difficulty of drawing conclusions based on current count data.