Friday, February 20, 2009
Common Raven Corvus corax
When we birded the Quabbin Reservation more regularly years ago, my wife D’Ann and I often saw and heard ravens. We had never seen a raven in Carlisle until December 29, 2002, the day of the annual Christmas Bird Count. On that day, D’Ann and Betty Valentine thought they saw a raven flying over Cross Street, and later I heard the hoarse “crr-ruk, crr-ruk, crrr-ruk” call of a raven near our house. Since that time we have seen them many times, and others have reported seeing them also.
Ravens are gradually expanding their range eastward in Massachusetts. The first confirmed nest in the state was found on a cliff in Cheshire in Berkshire County in 1983. Since then, ravens have nested in western and central Massachusetts, and by 2005 three nests had been found in southeastern Massachusetts. In the years between 1983 and 2005, 72 nests representing at least 68 pairs have been found in the state (1). As of 2005, the nest nearest to Carlisle was in northern Westford, about ten miles away. Two years ago, a pair of ravens built a nest on a radar tower in Waltham, but the nest attempt failed.
Ravens prefer to nest on cliffs, but will also use other sites. For several years, a pair of ravens has nested on a rocky ledge of a spillway near Winsor dam at Quabbin. Last May, during the Mass Audubon Bird-a-thon, we saw three young ravens in the nest, which was easily visible from a bridge over the spillway. Ravens also use tall trees (especially white pines), bridges and communication towers for nesting; they often use the same site, but not necessarily the same nest, for many years. Usually three to seven eggs are laid, and incubated by the female for 18-20 days. The male feeds the female during the incubation period, and the young fledge in 35-42 days (2). In New England, nesting usually starts in mid-February, and the young fledge by late May. A raven pair generally stays within their breeding territory throughout the year, and will try to drive off vagrant flocks of unmated or juvenile birds that attempt to feed in their territory (3).
Ravens eat a wide variety of foods, but mainly meat. They eat carrion of all types, including moose, deer and smaller mammals. They also capture live prey, such as small birds, rabbits, moles, chipmunks, mice and even short-tailed shrews, which have poisonous venom. While at Quabbin several years ago, we saw a pair of ravens carrying chipmunks to their nest at the spillway mentioned above. We wondered whether the chipmunks were found as road-kills, or if the pair had captured them live (pairs often hunt cooperatively). Ravens are also very fond of eggs of all kinds. Last May, I saw a raven flying with a large egg-shaped object in its bill, and just before seeing the raven I heard the gobbling of wild turkeys from our neighbor’s yard. Later that same morning, I saw a pair of ravens close together in a tree across the street. I suspect that the ravens had young and were raiding turkey nests for eggs. Bernd Heinrich relates a story of an Easter Egg hunt in Juneau, Alaska. Organizers placed 1,200 hard-boiled eggs around town a few hours before the event, but a group of ravens had been watching and by the official start time had taken most of the eggs. According to Heinrich, ravens frequent dumps in search of food, and are also fond of snack foods such as corn chips, potato chips and Cheetos.
In Alaska, ravens often associate with wolves in a symbiotic relationship. Their bills are not able to penetrate the hide of a large animal, and so they must wait to feed until other carnivores have opened the carcass. In return, the ravens may “guide” wolves (or other predators) to potential prey using their calls or behaviors. In New England, it is likely that ravens are benefiting from coyotes, which kill deer and other larger mammals. In the far north, ravens are less shy of humans, and will follow hunters hoping to obtain a meal of caribou or seal. Ravens also appear to be adapting to fast food outlets, at least in Alaska. Cathy Jones, who lives in Kotzebue, Alaska (about 200 miles north of Nome, 33 miles below the Arctic Circle), says that ravens enjoy eating McDonalds french fries at -40o F (4).
Thanks to Cathy Jones for permission to use her raven photo, Jason Forbes for information on the Waltham ravens, and Kay Fairweather for recommending Heinrich’s Mind of the Raven.
1. French, T. “Recovery and Biology of the Common Raven (Corvus corax) in Massachusetts”, Bird Observer, Vol. 34, No. 2, 2006.
2. Terres, J. K. The Audubon Society Encyclopedia of North American Birds, Wings Books, 1991.
3. Heinrich, B. Mind of the Raven, HarperCollins Publishers, 1999.
4. Cathy Jones’s blog:
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