by Carl Strang
It has been a while since I have shared one of my species dossiers. One of my practices is to keep records of what I have learned from my own observations of various species, as opposed to reading about them in other sources. Today I bring out my dossier on the Cooper’s hawk. In reviewing it I see that I have left out a lot of observations of this species, which has become common in the Chicago suburbs over the past decade or two, but those other observations would be much like the ones below. The observations begin with my date codes.
13SE85. Spring Valley Nature Center, Schaumburg. A Cooper’s Hawk pursued a frantic, cheeping young thrush in and out among the trees, in sharp twists, turns, and vertical climbs and plunges, for a good 15 seconds. Then the hawk broke off, and the thrush escaped. This took place in an old field between stands of trees. Could the cheeping have been a signal to the hawk that the thrush had plenty of wind? As soon as the hawk turned back into the woods, the thrush continued its flight over an open field.
2AP88. One passed through woods at Hartz Lake (in Indiana), occasionally calling “kip.” Flew and perched, flew and perched its way across woods.
12MR92, McDowell Forest Preserve. A Cooper’s flew, northerly, high above woods. Pursued by a crow that occasionally swooped at it, but the hawk itself was nearly crow-sized, and it often turned and flew at the crow. Flight faster and more twisty then, but the crow turned to pursue the hawk when the latter resumed its path. Three such cycles observed.
18AP92. Hartz Lake. Pair of Cooper’s hawks hanging around a clearing in the woods, often calling: a wild-sounding, almost woodpecker-like “eh-eh-eh-…” (15-20 repeated syllables).
20AU92. Cooper’s chased a couple crows at Herrick Lake F.P., not seriously. They rattle-called afterwards.
18MR99. An immature plumaged Coopers appeared, hung around the Willowbrook riparian area (SE corner of preserve) for the rest of March, calling frequently, but vanished in early April.
1SE99. Cooper’s hawk soared above Nature Trail area of Willowbrook, moving north to south. They soar from time to time.
15JE00. Morton Arboretum. Near Parking Lot 7, when I arrived around 8am, 3 robins were giving the high‑pitched thin call repeatedly, and the forest otherwise was relatively quiet. After 10 minutes, a Cooper’s hawk started calling nearby, then flew out away from the forest edge until an eastern kingbird started to chase it. It immediately turned around and flew back the way it had come, and kept going. The robins then were quiet.
16JE00. Willowbrook. In the afternoon, a Cooper’s hawk perched near the west edge of the prairie, drawing alarm calls from a robin (the hawk‑whistle warning call) and a cardinal, and a chorus of 7 loudly mobbing jays.
18JL00. Willowbrook. In the early afternoon, a Cooper’s hawk soared low above the marsh and areas east and west of it, while 3 red‑tails soared high. One of the visiting red‑tails called once, but the Cooper’s, which has been resident all summer, called repeatedly.
26FE01. A Cooper’s called for a long time from the top of a tree near the islands in the river at McDowell Grove. A harrier was flying overhead, but the Cooper’s did not appear to be looking at it while calling.
14AP01. 2 Cooper’s, possibly a pair, at West DuPage Woods. One made an unusual flight through the open air, with exaggerated, moth-like wingbeats reminding me very much of a short-eared owl.
5MY01. A Cooper’s hawk incubating a stick nest high in a tree at Wayne Grove Forest Preserve. Tail visible from below.
10JA02. Two jays newly arrived at Willowbrook (for weeks there had been one, at most, and these were in addition to that one). They were mimicking crow caws, with lower volume and a brighter tone that made the mimicry clear, but an interesting sound. One of them also repeatedly imitated a Cooper’s hawk’s calls, both the string of notes and the isolated single notes. Again the volume was lower than in the hawk, but tonal fidelity was very good. They were in brush, low to the ground and close to me (the Cooper’s imitator was within 20 feet and clearly knew I was there). Before long I saw a Cooper’s hawk, almost certainly the same one that we saw hunting the day before by sitting and waiting on a tree branch for a minute or 2, then moving to a new perch. Today the hawk was perched about 100 yards from the jays.
12MR02. As 2 Cooper’s hawks began to call in the woods at Willowbrook, a jay flew to the treetops above them and began the bobbing “teakettle” call. Another jay arrived and began to “jay” call as the first continued on away in the direction it had been going.
26OC07. A Cooper’s hawk still calling at Fullersburg.
2006-2008. Cooper’s hawks nested at Fullersburg. The great horned owls there prefer to use a hawk nest from the previous year. In at least one year the Cooper’s were successful, as fledglings frequently were to be seen. In at least one year, and perhaps two, the hawks started to incubate but then abandoned. In one case this happened shortly after a pair of broad-winged hawks arrived and began to advertise their territory nearby.
24MR09. Mayslake. Scattered feathers of a Cooper’s hawk in the prairie south of the stream corridor marsh. The location, and nature of feather damage pointed to great horned owl as the predator.
Late summer 09. Mayslake. One day a Cooper’s hawk caught a young-of-the-year robin in the woodland east of the mansion.
Autumn 09, Mayslake. A Cooper’s hawk, flying low, could see through the windows of the library wing, and attempted to fly through as it would a space within a forest canopy. Unfortunately the windows were closed. It was not flying fast, and after bouncing off flew away, apparently unharmed.
With the winter’s slower season arriving, I expect to be sharing more dossiers. I encourage any student of natural history to be careful in separating what you know out of personal experience from what you have heard second hand.
