Juenile Coopers hawk. Photo by B. Matsubara, Wikimedia Commons
(To listen to an audio version of this blog, please click on the following link … Cooper’s hawk
I was sitting at my writing desk working out the life cycle of the mite that causes scabies (it’s for next week’s blog about a mange epidemic in South America) when all of the sudden there was a commotion in the back yard. Perched on one of the metal cross pieces of my grandson’s climbing dome was a stunningly beautiful Cooper’s hawk!
She, and I am guessing that it was a female based on her size, had a white and chestnut brown, striped chest, a long light gray tail with three dark cross-lines and a darker, grayish-brown back and wings. She did not have a black cap, so my guess is that she was a juvenile probably trying to figure out what this hunting thing is all about!
She was chattering incessantly with a sharp-pitched, “kek-kek-kek” sound. She also kept lifting her right foot up from the metal tubing of the crosspiece and flexing it nervously. Maybe the metal bar was hot from the afternoon sun, or maybe she was just angry! She was trembling with nervous energy (from a close-miss on a kill, or at finding herself in a strange, way-too-enclosed environment?). Her yellow eyes were wide open and were darting back and forth across the yard.
Juvenile Coopers hawk. Photo by B. Matsubara, Wikimedia Commons
She reacted to something up in the honey locust tree and flew up into the branches pushing the dense masses of green leaflets out of her way. One of the fox squirrels hiding in the locust branches must have made a noise and attracted the hawk’s attention. The squirrel, though, reacted to the rising hawk in a very aggressive manner and leaped out at her before she could land in the tree. The hawk spun away and went to perch on one of the bare upper branches of a nearby sumac.
She must have come into the yard in pursuit of the flocks of house finches and house sparrows that have been gorging themselves (and all of their fledglings) at my sunflower seed feeder. Hawks, even young, inexperienced hawks, take a lot of fledglings, I am sure!
Cooper’s hawks are slightly larger versions of their fellow accipiter, the sharp-shinned hawk. They have very similar colorations and are tricky to tell apart, but Cooper’s hawks are 14 to 20 inches long (with females at the upper size end) while sharp-shinned hawks are just 10 to 14 inches long (again, with females at the upper end)
Female sharp-shinned hawk. Photo by D. Sillman
We had a pair of sharp-shinned hawks that were regular visitors to our yard and field back in Pennsylvania. Deborah even made a video one year of the female sharp-shinned hawk calling to her mate from the top of our black locust tree. The pair regularly picked off smaller birds coming into our bird feeders. (See More Notes on the Sharp-shinned Hawk (February 20, 2011).
Cooper’s hawks are also common raptors of backyard bird feeders all across North America. They are birds of woodlands and forests but have taken very well to the human-planted forests of suburbia and urban parks. They nest in mature trees usually 26 to 50 feet above the ground. Pines, oaks, spruces, beeches and almost any other type of tree of substantial size can serve as a nest tree for a Cooper’s hawk. The nests are piles of sticks usually wedged into the main fork of the tree. The stick mass is usually two or more feet in diameter and 6 to 17 inches thick and has a central, cup-shaped depression about 8 inches in diameter and 4 inches deep that is often lined with shredded bark or green twigs.
Deborah had just gotten into position by our back window to take the hawk’s picture, when a noise from our neighbor’s yard startled the bird and scared her away. It took the finches and the sparrows about ten minutes before they relaxed enough to come back to the feeders. The fox squirrel, though, stayed clutching his branch high up in the locust tree for many more minutes.
Photo by D. Sillman
Amazingly, the hawk came back the next day! She soared in across the low hanging branches of the honey locust tree and gave the fox squirrel that was lounging there (maybe the same one that leaped out at her the day before) a heart attack! The squirrel dropped to the ground and dove under one of our metal lawn chairs. The hawk landed first on the same cross-piece of the climbing dome that she had perched on yesterday but then flew over to the picnic table on the patio. After a few minutes, she flew over to the metal frame of our patio umbrella and then to the birdbath at the other end of the patio. She took a drink from the birdbath and then had a nice splash, dunking her belly feathers in the cool water. She hung out there for about fifteen minutes!
She looked very happy to be back in “her” yard!
Photo by D. Sillman
While she was splashing in the birdbath, the squirrel inched his way over to the spilled sunflower seeds under the bird feeder and started to eat! The hawk looked at him occasionally, but they both seemed to acknowledge the reality of their similar sizes and the improbability of an inexperienced Cooper’s hawk (about 1.2 pounds) trying to take a full grown fox squirrel (about 1.8 pounds).
Cooper’s hawks especially take medium-sized birds as prey. European starlings, mourning doves, Eurasian collared doves, rock pigeons, American robins, blue jays (and other types of jays, too), northern flickers (interestingly, the Cooper’s hawk call strongly resembles the call of a northern flicker!), quail, grouse, chickens and more are all on the “preferred” menu of this hawk. Very small birds (like house finches and sparrows) are usually not taken by Cooper’s hawk (although this juvenile in my backyard didn’t seem to know that!).
Cooper’s hawks have one brood a year. Usually a clutch is between 2 and 6 eggs, and, here in Northern Colorado, eggs are laid between mid-April and mid-May. Eggs are incubated (mostly by the female parent) for 30 to 36 days, and then the hatchlings stay in the nest for another 27 to 34 days until they fledge. After initial fledging, the young hawks still rely on their parents for food, but after another 2 or 3 weeks the parents “lose interest’ in feeding them and the young birds are on their own.
Photo by D. Sillman
We first saw our young Cooper’s hawk on August 18. Tracing back the 90 days or so through her egg, nestling and fledgling development stages, that would mean that she was probably from a early to mid-May clutch. She has only been on her own for a short period of time, and her hunting technique and prey preferences were not yet very well refined!
The hawk did not come back the next afternoon. The day after, though, I did see her land up in a large cottonwood tree about a block away. I hope that she has found some nice collared doves to dine on (they are really quite annoying and way too abundant!) and has left my northern flickers and robins alone!