Dark Morphs in Minnesota

Hi, everyone! My name is Allie, a graduate student at the University of Minnesota Duluth. Here in Duluth, fall migration is incredible, featuring high numbers of Red-tailed Hawks showcasing different plumages. Dark morph Red-tailed Hawks migrating and wintering in Minnesota are especially beloved by the raptor community.

Why is this?

Well, dark morph Red-tailed Hawks are not very common east of the Rocky Mountains. Western subspecies, like B.j. calurus and B.j. harlani, are polymorphic, meaning individuals can present dark, light, and intermediate plumages. In Minnesota, and all throughout eastern North America, Red-tailed Hawk subspecies, like B.j. borealis and B.j. abieticola, are currently known to be essentially monomorphic – only presenting variations of light plumage. Nevertheless, there are dark morphs observed during migration/winter in eastern parts of the Red-tailed Hawks’ geographic range. Thus, their rare presence is treasured and begs these two questions…

Which subspecies do these dark morphs represent, and where are they from?

In collaboration with Hawk Ridge Bird Observatory, I am collecting genetic material from all dark morph birds captured at Hawk Ridge in order to determine which subspecies they are more closely related to. Additionally, I am deploying satellite transmitters on three adult dark morph Red-tailed Hawks captured in Minnesota during migration or on the wintering grounds.

Featured below are the two birds we’ve deployed transmitters on. Manley (a second-cycle bird) was captured in Savage, MN in February and Trudi (an after third-cycle bird) was captured close to Duluth, MN last week. So far, we know Manley has summered (but probably did not breed) in northern Manitoba, and Trudi has made it as far south as Indiana within a few days! Here’s hoping we will get a better picture of their full annual cycle over the next several years. Stay tuned!

Manley

Trudi