Cornell Lab of Ornithology

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WINTER 1997/VOLUME 11, NUMER 1

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North American Shrikes
BY DIANE L. TESSAGLIA


Please cite this Page as:
Tessaglia, D. 1997.  North American Shrikes.  Birdscope, Winter 1997, Volume 11, Number 1:  3-4.


Although more than 70 species of shrikes exist worldwide, in North America we have only two—the Northern Shrike and the Loggerhead Shrike. Shrikes are not the kind of birds you’d expect to see on an average FeederWatch count day. Normally, these small predators rarely show up at bird feeders. But last year, shrikes were plentiful in FeederWatch yards, and participants from more than 27 states and provinces reported seeing shrikes at their feeders.

For some FeederWatchers, shrikes were welcome birds. Nancy Doherty of Michigan wrote, "We hang the rib cage of a deer with meat and suet scraps, and the shrike feeds on it daily through March—right next to chickadees, nuthatches, woodpeckers, and red squirrels." Other FeederWatchers were less thrilled. "A Northern Shrike killed my winter feeding program," wrote Bruce Soper of Manchester, Maine. "This hasn’t happened to me in 30 years of bird feeding."

Some people had unusual experiences with shrikes. Katherine Fricker of South Casco, Maine, wrote, "A Northern Shrike flew into the back of our Land Cruiser while we had it open. I caught him and held him while we verified the identification. (He bit me, so I got a good look at his beak while I held him in my hands!) After we let him go and had driven several miles, a Dark-eyed Junco flew out from behind the sun visor—which explains why the shrike had entered the car."

Shrikes eat mostly insects, mice, and small birds, but they will also scavenge for food. They capture their prey by either sitting still and attacking whatever appropriate prey item comes along or by actively chasing their quarry. Shrikes stun or kill prey with their heavy bills and then impale it on a thorn, twig, barbwire spike, or other sharp object. Shrikes—also known as "butcher birds" because of the way they hang up their food—are the only birds that engage in this unusual practice.

Unlike hawks and owls, shrikes do not have strong feet and talons, and they may be using the thorn or spike to hold their food fast while they eat. Other researchers believe that the shrikes may use their impaled prey to mark or define their territories. Still others suggest that shrikes impale their food to cache it for later use. Researchers have observed female shrikes with young feeding on cached prey near their nests. A strong similarity exists between the color of the prey and the color of the cache site, suggesting that shrikes may be storing their prey in particular places to hide it.

Loggerhead Shrikes formerly bred throughout most of the contiguous United States. The species has both migratory and nonmigratory populations, and although the nonmigratory population is common over much of its range, the migratory populations are listed as endangered or threatened. Data from the Breeding Bird Census show that Loggerhead Shrike populations in the Northeast and Midwest have decreased on average by about five percent each year since 1966. Nesting shrikes can no longer be found in New England, New Jersey, Delaware, or the District of Columbia. Causes for the birds’ decline vary. Modern agricultural practices—reducing the amount of pastureland, removing hedgerows from fields, using pesticides to increase crop yields—have taken their toll on shrike populations. Poor winter survival rates and collisions with motor vehicles have also contributed to these declines.

Throughout most of southern Canada and the northern United States, Northern Shrikes are irregular winter visitors. In winter, Northern Shrikes are found where the average minimum temperature in January is below 20 Fahrenheit (-7 C). They breed in the northern spruce forests. When food is scarce, Northern Shrikes wander farther south than usual. From 1900 until 1935, Christmas Bird Count data showed that Northern Shrikes would come south approximately every four years. Since 1935, the pattern has been less regular. Because they nest so far north, we know very little about their abundance on their breeding grounds. Thus, we rely on winter surveys such as Project Feeder- Watch to tell us about their annual movements and abundance.

 

 

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