Low Food Supply Alters Hawk Behavior
December 01, 2012
by Steve Grinley

     I would like to share with you some animal behavior as witnessed by Paul Roberts of Medford a week or so ago, along with some of Paul’s insight regarding the appearance of numerous Barred Owls in Eastern Massachusetts:

     “This morning I was watching Buzz and Ruby, the “185 Redtails“ in Cambridge, for two hours, studying how they responded to the appearance of a Barred Owl in a primary roosting and feeding area for them. It was very interesting, but that will be the subject of a Buzz & Ruby post on Arlington Birds in the very near future.

     “On the way home shortly after 8 a.m., as I approached the Route 2/16 rotary in north Cambridge by Alewife Brook, I spotted a juvenile Cooper‘s Hawk perched and diving into some vegetation on the north side of the rotary. The hawk perched again, prompting me to think of grabbing my camera off the seat next to me and photographing it through the windshield, as I was stopped by a red light. As I reached for the camera, the Cooper‘s again plunged several times into the vegetation. Immediately a large canid emerged from the shrubbery and began trotting across Route 16. The Cooper‘s Hawk continued to dive repeatedly at the canid, pursuing it across the highway and down towards One Alewife Place. (I could not hear or see if the Cooper‘s was vocalizing at the mammal.) Traffic and timing were such that I did not attempt to pursue them both by car, and could not park anywhere close to them. I called Amy Kipp, a friend who lives very close by, and she was able to see the hawk and photograph the canid, which had captured prey in its jaws.

     “When I first saw the canid trotting across one of the more congested highways in the Boston area, I thought fox; Red Fox. It was 95% overcast and the light was very flat, but I clearly saw a creature that looked gray brown. Not red. Although my first impression had been fox, it must have been a coyote, a small coyote. I saw the long fluffy tail; no white tip. Dark. I could not see any reddish hues. Probably coyote.

     “Amy Kipp, however, saw the critter and photographed it. A beautiful Gray Fox, with a prominent dark stripe down the top of the tail. I have seen only two or three Gray Foxes (that I knew) in New England in 40 years, and never imagined seeing one in Cambridge! (I seem to recall Oakes Plimpton reporting one in north Arlington several years ago.)

     “The sheer presence of Gray Fox is startling, but to see it being harassed by a juvenile Cooper‘s Hawk, striking it and flushing it across the highway at 8 a.m.. If that had been a weekday, when traffic in those lanes is backed up 8 blocks…

     “I‘ve seen similar behavior only twice before. Once I had a flock of magpies in Colorado mobbing some shrubs on the southern slope of the Black Canyon of the Gunnison. I wondered what all the fuss was about when a large Bobcat leisurely strolled down the trail, pursued by a growing flock of raucous magpies. Almost fifty magpies continued to dive into the shrubs, so I could follow the progress of the Bobcat down the mountain.

     “At Plum Island, I had an adult male breeding Osprey, whose territory, nest pole, and mate at the Old Pines had been challenged repeatedly during the day by migrating or other local Ospreys. When a large deer emerged from the shrubbery and started to stroll past the platform, the male Osprey began diving at the deer, screaming and striking the mammal repeatedly on the rump, driving the deer far out into the marsh, away from the nest pole.

     “I also questioned if this had any relationship to small mammal populations in the area. Barred Owls are appearing all over the landscape this fall, apparently due to a shortage of food, primarily small mammals, in the woods. This might be due in part to the failure of the acorn crop in 2011, which was forecast to lead to a 80+% decline of small rodents in the area. The Barred Owl at Lusitania Meadows, Fresh Pond, Cambridge, spent most of two days hunting in the meadow during the day time, and from my observations and reports from others, was seen to apparently capture only one rodent. It was actively hunting an area regularly hunted by two Redtails and at least one (possibly two) Cooper‘s. (Cooper‘s prey on small mammals as well as birds.) Both Redtails and the Cooper‘s had chased after the owl over the two days (and the owl chased after the Cooper‘s and one of the Redtails.) Was the Gray Fox exposing itself because of difficulty in finding prey? Was the Cooper‘s just aggravated by the presence of the fox, or was it trying to preserve feeding rights and prey (birds or mammals) because prey is especially tough to come by this fall? Don¹t know.”

Steve Grinley
Bird Watcher’s Supply & Gift
Route 1 Traffic Circle
194 Route 1
Newburyport, MA 01950
BirdWSG@Comcast.net 
978-462-0775 
www.birdwatcherssupplyandgift.com 
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