Periodic Invasions of Northern Goshawks

The Pick a Bird Brain series highlights research projects at Hawk Ridge Bird Observatory.
Registration is required for this presentation.

Dr. Dick Green, Professor Emeritus at the University of Minnesota Duluth, will look at historical observations made at three hawk watch sites: Hawk Ridge in Duluth, Minnesota, Cedar Grove in Wisconsin, and Hawk Mountain in Pennsylvania.

Ordinarily, hawk count sites do not see large numbers of Northern Goshawks during fall counts. However, about every ten years, the normal patterns change in significant ways and is called an invasion. What is an invasion and what might be responsible for this dramatic change?