It’s been a really good year for Rough-legged Hawks so far. I have seen 6 in Centre County and 5 more across Pennsylvania and they are being reported in many locations across the state. While there have been Rough-legged Hawks in the grasslands along 220, most of them have been brief glances or distant views. Most have also been light or intermediate morphs. Last week I managed to get much better looks at a dark morph which was a treat.
The percentage of dark morphs to light morphs follows Gloger’s rule which states that more heavily pigmented forms of species tend to be found in more humid environments. From a survey of museum specimens, in the Aleutians and sw. Alaska, dark morphs were 19%, 3% in w. Canada, and 12% in e. Canada. Data from hawk watches showed 6% dark morphs in the west (Alberta) while 18% and 26% in the east (Whitefish Point, MI and Marathon, Ontario respectively). Our birds are likely coming from eastern Canada so we should expect to find 1 dark morph for 3 or 4 light morphs.
I think that this is a dark morph adult, possibly a male. I would appreciate any comments and corrections on the age of this bird.
