Friday, December 5, 2008
Northern Shrike (Lanius excubitor)
The Northern Shrike is an uncommon winter visitor to the United States. It breeds in the
boreal forest/tundra ecotone from Labrador and Quebec to western Alaska. In Carlisle, we usually see them perched near the tops of trees within or bordering open fields. Good places to look for them in Carlisle are at Great Brook Farm State Park, Great Meadows NWR (former O’Rourke Farm), Towle Field, and Foss Farm. I saw a juvenile shrike near the top of a tall tree along the Acorn trail at the State Park on November 5.
According to Bent (reference 1), “Shrikes look superficially somewhat like chunky mockingbirds with thick heavy heads and bills, but there is a black band on the head, through and behind the eye … there is also much less white in the wings and tail, and the latter is proportionately shorter than in the mockingbird.” The plumage of juvenile shrikes is more brownish than gray. If you get a good look at the shrike’s bill, you will see that it is hooked, like that of a raptor (see photo).
An early common name for the shrike was “butcherbird,” because it often impales its prey on a thorn or twig. Lanius is Latin for “butcher” and excubitor means “watchman or sentinel,” a reference to its habit of scanning from a high perch.
Shrikes are strictly carnivorous, and prey on small birds, mice and insects, especially grasshoppers. We have never seen a shrike capture its prey, but I once saw a shrike at Foss Farm flying with a small bird in its talons. In Louisiana, the home of a different species of shrike called the Loggerhead Shrike, we sometimes saw small birds impaled on thorns and barbed wire, stashed by the shrike for later consumption.
Ken Harte’s data for the Carlisle sector of the Concord Christmas Bird Count (CBC) show Northern Shrike reported in 12 out of 35 years, starting in 1973. The high count was four individuals in 1995. Shrike numbers vary from year to year, depending on the number of young produced and availability of prey species farther north. In Carlisle, we usually begin seeing shrikes arrive in early November and staying as late as early March.
Attitudes about the desirability of certain bird species change over time. Veit and Petersen comment: “It seems ironic to note that shortly after House Sparrow were introduced to Boston, a warden was hired to shoot Northern Shrikes on the Boston Common in order to protect House Sparrows. The warden shot upwards of 50 shrikes in one winter on the Boston Common (probably circa 1878-1879, Brewster 1906).”
The writer thanks John Carlson for permission to use his excellent photograph, and Ken Harte for providing the CBC data used for this article.
1. Bent’s Life Histories from “Wild Bird Omnibus”: www.birdzilla.com
2. Veit, R. R. and Petersen, W. R. Birds of Massachusetts, Massachusetts Audubon Society, 1993.
3. Gruson, E. S. Words for Birds, Quadrangle Books, 1972.
4. John Carlson’s blog: http://prairieice.blogspot.com
© 2008 The Carlisle Mosquito