Eastern red-tailed hawk

The race breeds below the Arctic (unlike more western birds which can reach the sub-Arctic as breeders), and is absent from all but the southernmost part of the Hudson Bay and roughly the northern third of both Quebec and Newfoundland. Wintering migrants from southern Ontario may range east to southern Maine and south to as far as the Gulf Coast and Florida. The western limits of this race's range are slightly ambiguous and they may hybridize extensively with the western red-tailed hawk (Buteo jamaicensis calurus) in timbered stretches of the Great Plains. The breeding range of B. j. borealis seems to include most of Texas (perhaps excluding the western sections), Oklahoma, Kansas and Nebraska. In the Dakotas and even eastern Wyoming, some B. j. borealis may occur but give way mostly to B. j. calurus and/or Krider's hawk (B. j. kriderii), with the B. j. borealis type hawks breeding without race mixing to the western border of Minnesota and the eastern third of Manitoba. ==Description==

This is a large-bodied, relatively heavy race, but differs from more westerly hawks in having a relatively smaller wing area. Based on linear dimensions, this subspecies shows the most size variation and, unlike the red-tailed hawk species overall, size variation seems to fall within Bergmann's rule as northern birds average larger than southern ones. The wing chord of males can range from , averaging , and, in females, it ranges from , averaging . Additionally, males and females average in tail length, in tarsal length and in culmen length. The largest known sample of body weights from unambiguous B. j. borealis was from Wisconsin migrants, with 34 males averaging and 24 females averaging . == References ==