The pesticide DDT was the main cause for the demise of the Peregrine, because it caused peregrine egg shells to be thin and to break easily. In the late 1970s falconers from Cornell University in upstate New York began breeding and releasing falcons to the wild. The first Midwest peregrine release occurred in 1982 near Weaver Dunes in southeast Minnesota. Unfortunately, these early efforts proved unsuccessful because great-horned owls preyed on the released falcons, he said. Urban sites have since been used for releases because tall buildings can provide updrafts that simulate the bluffs of northeast Iowa, and Great-horned Owls are not as prevalent in urban settings.
Efforts are underway to release peregrines in the rocky bluffs of northeast Iowa.
This year a male peregrine from the 1998 Effigy Mounds release has mated with a female falcon released from Mason City in 1998 and are currently nesting at Queen's Bluff in southeast Minnesota. This majestic bird has returned and we can hopefully appreciate the lessons that environmental contaminants can have on all of us. For the third year in a row, the Iowa winter bald eagle survey counted about 1,700 mature eagles in Iowa. Boone wildlife research station. Despite stable counts the last few years, this year s numbers were down a little, Ehresman said.