Hawks We Have Seen

The other day I was out looking for dragonflies when I saw this beauty in the tree just above me.  She (I think it was a she because it was a BIG bird) was sitting at the edge of a grassy old field full of wildflowers, scanning for mice or snakes or frogs or whatever appealed to her at the moment.  And she was completely oblivious to my creeping up on her to take her picture. 



This is an adult Red-tailed Hawk (you can tell by the red tail -- duh).  This species is one of my favorites.  Years ago I published (an interesting, I thought) paper about them, comparing their daily energy budget with that of their temporal counterpart, the Great Horned Owl.  Both species are common and are year-round residents all over North America, meaning they stick around throughout the nasty winter as well.  Unlike the owls, however, Red-tailed Hawks will lower their body temperatures at night during the winter when they run short of food and have failed to eat for several days.  This mild hypothermia allows them to balance their energy budget.  Perhaps being a nocturnal hunter allows owls to have greater hunting success, because their body temperature is absolutely stable at very cold temperatures, even when they are food-deprived.  Like humans, the feet and the head are two key areas of heat loss in hawks.  Both areas are well insulated by feathers in owls -- that might make a difference in the cold.  Check out those sharp talons in this picture (click on it to enlarge).  Could anything escape these pinchers?

Like many birds of prey, these hawks enjoy really superb binocular, color vision that enables them to pick out the tiniest moving objects in complex backgrounds.  In addition, they have two different fovea (focus spots) in their retinas, one in the back of the eye like us, and one near the top of the eye, which allows them to focus on objects below.  I finally got too close to this bird, and she began to focus on me, as you can see here.  She sort of looks cross-eyed.