Cooper’s Hawks

The Cooper’s hawk, Accipiter cooperii, is a woodland inhabitant and hunter.  In Illinois, they were state listed as endangered from 1977 to 1997.  Since then, with less pesticide use in the environment, we are seeing more of them in backyards here and across North American urban areas.

Cooper’s hawks are blue-gray on the back,  with a black cap, and a belly of white with rufous streaks.  The tail is long and  rounded with black horizontal bars.  Hooked bills for tearing, needle-sharp talons for grabbing prey, and forward-facing eyes providing good depth perception contribute to making this bird an excellent hunter.  They approach stealthily, or sit and watch, then attack with a burst of speed.  Using their tails as rudders, Cooper’s hawks are able to turn quickly and sharply when in flight, giving them outstanding chase and catch abilities while on the wing in a wooded habitat.  Chases can become intense, and several birds have been found to have cracked or broken ribs from encounters with tree branches.

Cooper’s Hawk [back], Accipiter Cooperii by Alan D. Wilson, 2010

Historically, these birds nested in woodlands with extensive canopies and ate songbirds feeding in agricultural row crops.  Many birds have moved to living in urban settings, favoring white pines and oak trees that offer good canopy coverage.  Individuals are loners except at breeding time in the mid-spring.  Males will build a simple nest, and females will lay 2-6 white eggs.  Females incubate the eggs for four to five weeks, then both parents teach the young to hunt.  Juveniles are fully independent and able to live on their own after five weeks.  Egg predation is minimal, with the average clutch losing 25% or fewer of its eggs.  First year mortality rates are high, around 70%, but drop off quickly to 30% for adults.  The average life span in the wild is comparatively long at eight years.  Many birds die from mid-air collisions with wires, autos and windows, especially in urban settings.  Birds are susceptible to a number of bacterial diseases, which may impair the birds’ abilities, but are normally not deadly.

In Illinois, there are populations that are year-round residents, and there are migrating populations in both spring and fall.  Resident birds may move 50 to 150 miles for short periods depending on temperature and storms, and then move back again.  Spring migrators leave the southern parts of North America headed for breeding areas across Canada for the summer and return in fall to warmer climates.  Our best data on population numbers for this species come from the Christmas backyard bird count and individual watchers journaling their daily observations.

Cooper’s hawks eat small to medium-size birds including cardinals, sparrows, doves, robins, and starlings.  They will also supplement this fare with small mammals such as field mice and squirrels, and other prey including snakes and toads.  With the rise in backyard bird feeding and the restoration of natural areas across the state, birds of prey and Accipiter hawks in particular have become common urban residents.  Two other Accipiter hawks that share habitat and hunting ranges with the Cooper’s hawk are sharp-shinned hawks and Northern goshawks.  These hunters may be considered a natural biological control for larger populations of birds such as sparrows and starlings, but hawks are generalists with their prey and may pose as big a danger to rare birds, as well.

Cooper’s hawks are more active in early morning hours, and they are considered one of the top daytime predators.  As you watch your feeders this winter, be aware of this opportunity to observe a skilled hunter in flight.  They are exciting to observe, sitting close up in a backyards or chasing prey through the trees.