Close Encounters: Cooper's Hawk and Sharp-shinned Hawk

There is a life and death drama being played out in my yard. From my kitchen and living room windows I have the best seat in the house.

Meet the killers. The first is an adult Cooper’s Hawk, which I have judged to be a male by his size. He has been visiting my yard at the base of Silver Star Mountain, Vernon, since mid November. He favours the neighbours’ big maple tree because a perch halfway up gives him a commanding view of my yard where I maintain a bird feeder.

Fig. 1 - The Cooper's Hawk in my yard 31 Jan. 2017

Actually, bird feeding station is more accurate than calling where I put seed a “bird feeder". Every dawn I scatter about a dozen cups of mixed bird seed on and around a big round piece of an old Siberian Elm that was felled and cut up a few years ago. The pseudo stump sits at the base of a little patch of lilacs growing next to a sprawling ancient apricot tree. Lilac and apricot are growing more or less directly below the maple.

Fig. 2 - The feeder area. The plastic dish is used for a bird bath in the mild months.

Meet the second killer. He’s a Sharp-shinned Hawk, also an adult and also a male. He visits the yard as well, but rarely on the same days as the Cooper’s and never, to my knowledge, at the same time.

Fig. 3 - Sharp-shinned Hawk in my yard. Note how its expression differs from that of the much larger Cooper's Hawk . 

Attending my feeding station are Black-capped and Mountain chickadees, a couple of Red-breasted Nuthatches, one female Downy Woodpecker, and up to three Northern Flickers. These birds have no part to play in my story because so far they have been ignored by the killers or have evaded them so successfully that it’s unlikely they will be caught.

Also faithful to the feeding area are California Quails (up to 40), Eurasian Collared Doves (up to 5), Mourning Doves (up to 37), Dark-eyed Juncos (30), Song Sparrows (4), House Finches (8), American Goldfinches (5), and House Sparrows (20). The quail and the doves are of much interest to the Cooper’s Hawk and the sparrows, juncos, and finches clearly fascinate the Sharp-shinned Hawk.

On 15 Dec. 2016 the Cooper’s Hawk appeared in the maple early. It was a gloomy morning, valley fog over the North Okanagan, and the hawk blended well into the shadowless murk. With his gray back to the line of California Quail that were slowly infiltrating the lilac hedge off to the hawk’s right, he must have been harder than usual to see. Whatever the reason, the quail seemed not as wary as usual.  At 10:51 the hawk suddenly leaned right, propelled himself off his perch and with two or three power flap peeled around the end of the hedge and struck a female quail on the back. His momentum carried him on top of her, and though she struggled he kept at least one large foot clamping her body to the snow.

Fig. 4 - Cooper's Hawk has taken the California Quail into the skimpy shelter of the lilac hedge.

Fig. 5 - Halfway through his meal.

Fig. 6 - Almost finished.

Fig. 7 - 52 minutes from the time of capture, the hawk takes his first break from plucking and eating.

Once on his prey he looked around intently probably to make sure that he was safe from attack or interruption. Keeping the quail gripped with one foot, he peg-legged his way into base of the lilacs and began plucking his prey. Fortunately the hedge was thin enough so that I could see the hawk and his prey quite clearly from a living room window. He began plucking the quail only about 3-4 minutes after seizing her. In Figure 4 the quail is on its belly, its head buried in the snow as the hawk grips it on the lower back beneath the wing.

Plucking and eating the quail took about 50 minutes. At which point the quail died I do not know. I hope it expired almost immediately, but some tell tale shifting of the hawk upon its prey suggests that the quail may have struggled a few minutes even while in the hawk’s grasp.  This led me to the question, how does a Cooper’s Hawk or other accipiter actually kill? I found an answer in Leslie Brown’s classic text Birds of Prey. Referring to high speed photographic studies of striking raptors studies carried out by the ironically named G.E. Goslow, Brown describes the strike of the Cooper’s Hawk and that of a Northern Goshawk:

                  Both accipiters attacked in essentially the same way. They first gained speed by vigorous flapping, [then] ceased flapping, the Cooper’s Hawk at 3.5 to 4.5 metres and the Goshawk at 7.5 to 9 metres. Still closer the hawks swung the body upwards to bring the pelvis beneath the head, spreading the tail to brake, and at the same time threw the feet forward hard. At the actual instant of strike, the feet were traveling towards the prey at almost or more than twice the speed of the head. In the Cooper’s Hawk, the relative velocities were 4.8 metres per second for the head and 11.4 for the feet…by thrusting the pelvis and feet forward, the striking accipiter delivers a violent blow at the prey and does not just grab it with outspread feet…To kill their prey these accipiters used a kneading action of the talons, something like that of a contented cat on a lap. Pp 123-124.

Although his final simile strikes me as not quite appropriate, I think you understand a little more clearly now how a Cooper’s Hawk strikes and kills.

From about 10:55 to 11:47 the Cooper’s Hawk plucked, tore apart, and swallowed the quail bit by bit. The area immediately around the hawk became feather-strewn. He paused only once to watch the neighbours leave in their vehicle and twice to scrape particularly bothersome feathers from his beak. His first real break from eating came at 11:47 when he sat for 3 minutes in the centre of the feathery circle, presumably fairly replete. (Fig. 7). 

A nosey Black-billed Magpie approached the hawk within 2-3 metres. The hawk peg-legged out onto our lawn (for a clear runway) and flew with the tattered remnants of the quail still in his grip to the maple and a few seconds later into a dense Douglas-fir hedge. The magpie lost interest and flew off. About three minutes later at 12:06 the Cooper’s Hawk returned without the quail skin to the maple, where he perched, crop bulging, for an hour and a half before flying off for the day.

Figure 8 - The Cooper's Hawk resumes his perch in the maple and begins to digest his meal. Note the bulge in his crop. 

The Birds of North America revised account of the Cooper’s Hawk describes three  methods of attack. Cooper’s Hawk sometimes stoops from high flight, like a Peregrine might do. This has to be a fairly rare hunting technique. I say that because I don’t know of anyone who has seen such an aerial attack. In the second method, a Cooper’s Hawk puts on a sudden burst of speed as it leaves its perch. This describes the kill that I had witnessed. Finally a Cooper’s Hawk can hunt on foot, entering even thick shrubbery after birds, an approach toward securing prey also employed by the Cooper’s smaller cousin, the Sharp-shinned Hawk.

My Sharp-shinned Hawk showed up in the yard on 6 January. For his first few visits, I saw him only as he briefly passed through the yard, but finally on 13 January he stuck around to try some hunting. In my ebird entry for that day I called his hunting technique “drop and hop”.

Like the Cooper’s Hawk, at first the Sharpie perched in the maple, but there the similarities between hunting styles ended. When he spotted potential prey, usually among the juncos, finches or House Sparrows, he did not push off in power flight, but simply appeared to drop the few metres down to the lilac growing beside the feeding area. Invariably some of the songbirds bolted into the many stemmed lilac around which the Sharpie now fluttered. He would perch on slender ends of branches then fly in a tight circuit around the bush, wingtips almost brushing the twigs. Frequently he dropped to the snow and half hopped half flapped around the base of the bush, reaching between stems trying to snag one of the small birds sheltering within the bush’s base.  If small songbirds dream, their nightmares might feature a surprisingly long slender leg ending in a long-toed foot armed with wicked talons able to reach through even the tightest cage of stems and grab at them.

Fig. 9 - Sharpie, eyes on the prize,  just about to drop and hop. 

The Sharp-shinned Hawk made far more hunting sallies per day than did the Cooper’s Hawk. While the Cooper’s Hawk waited sometimes hours before attempting a hit, the Sharp-shinned Hawk was willing to try his luck whenever small birds gathered at the feeder. However, his success rate was nil at least while I was watching. All of half dozen or so attempts that I witnessed over the next few days failed until 8:59 AM, 15 January 2017 when he dropped, hopped, and plunged through the twigs to pin to the snow a White-throated Sparrow that was just too slow to avoid him. Through a kitchen window I was able to snap one picture of this capture before the hawk flew away with his prize in his talons.

My attitude towards raptors was tested very briefly. Normally as when the Cooper’s Hawk caught the California Quail, I thought that I remained objective, neither pro-hawk nor pro-prey. I dressed my supposed neutrality in reasoning that death by hawk was Nature’s way. That’s why there were so many quails and so few Cooper’s Hawks. In the grand scheme, quails were hawk chow. However, when the Sharp-shinned Hawk snatched the only White-throated Sparrow ever to attempt to overwinter in my yard, my single thought was, ‘What! You nailed the White-throated Sparrow! You couldn’t grab one of the common species? Come on, Sharpie. That’s not fair!’

Fig. 10 - The White-throated Sparrow was just too slow trying to get away from the base of the lilac bush. 

My indignation didn’t last long though. The thought intruded that far from being neutral about the life and death struggles in my yard, I had been pro-raptor all along. After all, there was nothing natural about my feeding station. It was an artificial concentration of seed, attracting a concentration of quails, doves and other species unlikely to occur in such high numbers without human intervention. Lots of avian activity attracts accipiters according to scientists E.L. Dunn and D. Tessaglia. 

However, their study of Project Feeder Watch also expressed the idea that successful kills are quite rare. And, for me, truth be told, the sight of a hunting accipiter, buteo, harrier, eagle or falcon quickens my pulse as no quail or sparrow ever can. Let me be clear: I am not feeding birds just to feed raptors. I like having ALL species around the yard, but if I am going to continue feeding birds I might as well be honest about my feelings.  Raptors, whether they are Cooper’s Hawk, Sharp-shinned Hawks, or Pygmy Owls, kill birds coming to my feeder so rarely that I don’t think I am upsetting anything in any major way. But each of us who feeds birds must make up his own mind about the effects of feeding birds in the backyard, a backyard that can become the setting for a life and death drama.

References:

Bildstein, Keith L. and Kenneth D. Meyer. 2000. Sharp-shinned Hawk (Accipiter striatus), The Birds of North America (P.G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America. https://birds.org/species-Account/bna/species/shshaw. DOI 10.2173/bna. 482

Brown, Leslie. 1976. Birds of Prey: Their Biology and Ecology. The Hamlyn Publishing Group, Middlesex, England.

Curtis, Odette E., R.N. Rosebfield and J. Bielefeidt. 2006. Cooper’s Hawk (Accipiter cooperii), The Birds of North America (P.G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America; https://birdsna.org/Species-Account/bna/species/coohaw DOI: 10.2173/bna.75

Dunn, Erica L. and  Diane L. Tessaglia. 1994. “Predation of Birds at Feeders in Winter.” Journal of Field Ornithology 65 (1) 8-16.