The name songbird conjures up an image of a colorful singing warbler. But one family of songbirds, the shrikes, are fierce little predators. No bigger than a robin, shrikes mainly eat insects, especially grasshoppers and crickets, but they also prey on rodents, small birds, lizards, snakes and frogs.
Utah has 2 species of Shrike: the Loggerhead which resides here year round and the Northern which breeds in tundra and visits Utah in the winter. Shrikes prefer semi-open country that has some trees, shrubs or fenceposts where they perch to watch for prey and then swoop to kill with their thick hooked bill.
Shrikes are sometimes called butcher birds from their habit of impaling their prey on thorns, the spikes of barb-wire or any available sharp object. Numerous explanations have been posed for this behavior. Shrikes may be storing food for later consumption and perhaps letting it decompose a bit to tenderize. They could be advertising their territory or holding the prey in place, the better to tear apart into convenient sized bits. A study in Florida provides an interesting insight. Lubber grasshoppers and their kin possess nasty toxins. Animals that dare to consume them gag, vomit and sometimes even die. Researchers discovered that these toxins degrade when the dead grasshoppers are left impaled for a day or two, providing the shrike with a meaty meal that no one else wants to eat.
Populations of Loggerhead Shrike have been slowly declining over much of their range in the United States. One reason appears to be habitat destruction, particularly the relentless conversion of grasslands to suburbs as well as more intensive farming practices. In the Intermountain West, the noxious weed, cheat grass, is another culprit. Where cheat grass has invaded, fire is too frequent for the natural vegetation to recover. The Loggerhead Shrike is an indicator species for the health of the shrub-steppe ecosystem. Its declining numbers tell us that too much good habitat has been altered or lost.
This is Linda Kervin for Bridgerland Audubon Society.
Image: Courtesy and Copyright © 2013 Linda Kervin, Bridgerland Audubon Society
Text: Linda Kervin, Bridgerland Audubon Society
Shrike, Wikipedia.org, http://en.wikipedia.org/wiki/Shrike
Davidowitz, Goggy, Grasshoppers, Arizona-Sonora Desert Museum, http://www.desertmuseum.org/books/nhsd_grasshopper_new.php
Loggerhead Shrike, All About Birds, http://www.allaboutbirds.org/guide/loggerhead_shrike/id
Northern Shrike, All About Birds, http://www.allaboutbirds.org/guide/northern_shrike/id