by Carl Strang
Here is another, relatively long, entry in my series of species dossiers, accounts of what I have learned of various species from my own experience. In sharing these I am less interested in transmitting information than in encouraging you to think about what you know about these animals from what you have observed. When I started these records in the 1980’s I was embarrassed by how little I could say, and developing them was a good exercise in paying better attention when in the field.
Abundant around Culver, Indiana, in Cumberland County, PA, and [formerly] in DuPage County, IL. Strictly rural in the Culver area when I was a child, staying out of town [though this no longer is the case]. In PA, occurred in and out of town, but more typical of drier uplands and agricultural areas (the fish crow was more common in town and around rivers). In DuPage County, IL, American crows were abundant in both town and rural areas. They spend times in all habitats, though they stay up in trees when in the forest, usually. They spend more time in open, drier habitats than in others.
Their diet is equally diverse. I’ve seen them take corn sprouts, insects, young birds and rabbits, and carrion. In DuPage County they were the principal avian scavengers; vultures are practically nonexistent except during migration. Road kills are the most commonly observed food there. In late winter 1986 I saw a group of crows feeding on smooth sumac fruits, along the road at Warrenville, IL.
Crows nest solitarily, in the highest levels of forest trees. Vocalizations include a feeding call of young, a whining sound with somewhat the quality of a played sawblade: ree ree ree reereereereeree. This call accelerates and becomes slightly higher pitched and squeakier toward the end. Adults’ single “caws” appear to be contact calls. Harsher, sharper rapid clusters of caws are signals that rally crows to mob hawks or owls. This is a social, flocking species for most of the year, though spreading out when foraging for widely scattered foods like insects in short grass.
In DuPage County, crows mob great horned owls most frequently. Usually a mobbing begins with a single crow spotting the perched owl, and giving the rallying call. As more crows gather and add their voices, they perch all around the owl and the noise gets very loud. Usually the owl just sits stoically, but if it flies the crows give chase, sometimes one or two so bold as to peck the owl on the back. Eventually they lose interest, and silently fly off in one’s and two’s. Crows themselves are the objects of aerial harassment attacks by red-winged blackbirds.
Tall dead treetops with many branches in woods often are congregation sites.
10JA80. Boiling Springs, PA. In the afternoon I watched a crow chasing a kestrel. The birds flew high, and the crow stayed right with the little falcon’s twists, turns and dives. Finally, the crow broke off after the chase had carried the two a couple of hundred meters from the starting point. The crow flew back there, and the Kestrel flew a parallel course 50m away, but continued out of my field of view.
22FE87. Flock of 15 crows, flying. Cawing a lot, caws a little short though they aren’t chasing anything. Occasionally one utters a low, dry rattle. Later a loose group of four flew, taking turns making sets of 3-4 connected sharp caws. When calling, an individual folded his wings slightly and glided at a slight angle downwards.
14MR87. Signs of breeding. One, after cawing as though after an owl (none right there) broke off a twig from a treetop and flew away with it. Later a crow closely chased another out of that part of the woods. The chase went for at least 100m.
15MR87. Crow flying with beakful of soft material.
29AP87. Remains of a crow beneath great horned owl nest area.
16JA88. (McDowell?) Great horned owl flew to tree on west bank, just north of where trees thin to a thread of willows, where a housing development comes down. There’s a top-blown tree nearby, also several large oaks. Crows raising a ruckus, as though pestering a g.h. owl. From that direction a red-tailed hawk soared, but they paid it no heed. It circled an adjacent riparian strip, but when the owl finally broke and flew with a flock of 10 crows in pursuit, the hawk fell in between, and began to chase the owl, itself. Once it got above the owl and swooped at it, brushing the owl’s back with its feet, but about then the crows caught up and chased both raptors down toward where I had seen another owl perched, now out of my sight.
21MR88. Crows have been molting wing and tail feathers. Still chasing each other.
10AP88. 3-5 harsh, medium-fast caws apparently means “human here.” Several circled me at Hidden Lake F.P. woods, some perched in treetops above me and peered down, making that signal.
14AP88. Spotted 2 crow nests along Butterfield Rd., one beside construction site in a small grove of 30-40-foot-tall trees, the other well up in one of a grove of large oaks.
7MY88. Culver, IN. 2 nests high in oaks of “Indian Trails” area between town and Culver Military Academy. Adults flew off silently.
17MY88. I hadn’t seen the great horned owls of Willowbrook’s Back 40, or heard harassment by crows, since the restorational clearing of the marsh and fill area. Finally I saw 2, upstream of nest. Crows didn’t harass them for long or in numbers (2-3), apparently too occupied with their own nesting activity.
Harassment picked up, gradually, in June. On 18JE88 I observed heavy harassment of a great horned owl by a large number of crows at McDowell Grove F.P. Owl’s branching comes at the same time crows are starting to nest, and becoming too busy to harass owls.
18AP(MY?)88. The notes of a crow’s “human” call may be uttered rapidly when given as a warning. I walked into a riparian strip, one crow gave that fast version as I approached, and another immediately flew up from the streambed where it could not have seen me.
23MY88. Crow carrying medium-sized ear of dried corn, with about half of corn still attached, in beak.
29JA89. The crow mobbing call is a drawn out, often slurred, slightly burred caw, but retaining the abrupt start. (Another crow flying in, when still at a distance, gave a single note of this type but lazier, more drawled sounding, because it lacked the abrupt start and because it was more drawn out.)
7FE89. Permanently disabled crows in the exhibit cage at Willowbrook Wildlife Center responded to a “visiting” red-tail with short, uninflected (flat) caws with somewhat sharp beginnings but open ends. Fairly rapid, but not chattering-like, not clearly strung together. Many notes, long-continuing.
12MR89. A crow near Hartz Lake (Indiana) carrying a twig.
13MR89. DuPage County. Crow nest, same cluster of trees but farther back from busy Butterfield Road, as last year.
21AP89. A crow nest in downtown Chicago, in the little park across from the Newberry Library. I seldom have seen crows in the city. One bird visited the nest while I watched, but did not switch with the incubating crow.
25AP89. At end of a brief chase between 2 crows, one (I believe the pursued) gave a rattle-call. But I’ve recently heard the call from a bird perched for a long time.
10MR90. Crow with twig in beak, flying straight and parallel to road at 25mph.
30AP90. Crow chasing crow: a rattle call by the pursuing bird, with an emphatic inflection within.
12MR92, McDowell Forest Preserve. A Cooper’s hawk 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.
20AU92. Cooper’s chased a couple crows at Herrick Lake F.P., not seriously. They rattle-called afterwards.
24JA93. Warrenville Grove Forest Preserve, IL. In late morning on a cold, sunny day, a goshawk flew past as I crossed a brushy opening in the forest. The bird was low, perhaps 10 feet up, and abruptly dipped, then flew up to a 15-20-foot-high perch on a large branch of a tree at the edge of the clearing. I came within 40 yards or so; the bird watched me but did not fly as I turned and skirted its position. Crows passing over gave several sets of quick, paired caws: “caw-caw, caw-caw, caw-caw,” merging in some cases into a fairly rapid series of cawing notes. This was not a response to me. Long after I left the site, I heard the same paired caws and looked back to see that the crows emitting them were circling above the goshawk’s position. The crows stayed at an altitude of ~1.5 tree-heights; the hawk was perched between 1/3 and ½ the trees’ height.
27JA97. Morning. Snow fairly deep. A red-tailed hawk flew over the College of DuPage parking lot with something in its talons, pursued by half a dozen crows. The hawk perched on a flat-topped, wooden light pole, began plucking prey while crows sporadically left nearby perches and swooped at it. After 10-15 minutes it flew away, and I checked the feathers, which were scattered in singles and small clumps over a 20×30 foot area: mourning dove. Crow calls resembled owl mobbing, but smaller number of birds and less sustained.
1997-98. I occasionally see a white crow as I drive to work at Willowbrook Forest Preserve, the bird on either side of Park Boulevard a short distance north of Butterfield Road.
15MR99. Crow flew across Butterfield Road near Naperville Road crossing, north to south, with sticks.
14AP99. Willowbrook. Crows seen chasing one another several times.
4MY99. At mid-day, a flock of 8 crows pursuing an adult great horned owl over much of Willowbrook Preserve.
25MY99. Blue jay mobbing a perched crow in top of dead willow, Willowbrook.
9DE99. Crows pursuing a red-tailed hawk in NE part of Willowbrook preserve.
2010. In recent years, crows have become scarce in DuPage County, apparently because of a lack of immunological resistance to West Nile Virus. The pattern seems to be that new birds disperse into the area in winter, and may attempt to nest (but this isn’t common as far as I can tell, supporting the idea that these are young, dispersing individuals). When conditions support the emergence of West-Nile-carrying mosquitoes in late summer, the crows vanish, apparently victims of the disease. Supporting this notion is the observation that in the cooler wetter summer of 2009, more crows persisted into the fall.