Wednesday, July 20, 2016

Predatory Passerine: Loggerhead Shrike

Provided by American Bird Conservancy

The husky, predatory Loggerhead Shrike is nicknamed "butcherbird" for its habit of skewering prey on thorns or barbed wire. "Loggerhead" refers to the large size of this bird's head in relation to its body.

This shrike's song is a bit like a mockingbird's, featuring a series of raspy, buzzy notes and trills. Along with the bird, that song has become much less common. According to Breeding Bird Survey data, populations have declined by almost 80 percent since 1966. This trend coincides with the introduction of chemical pesticides in the United States.

Shrike's Steep Decline
The Loggerhead Shrike is recognized as a "common species in steep decline" on the 2014 State of the Birds Watch List. Other likely causes of its population decline are habitat loss, collisions, and human disturbance.

There are 11 recognized subspecies of this bird, which is the only member of the shrike family endemic to North America. The subspecies of Loggerhead Shrike from San Clemente Island, in southern California, is considered endangered.

Hunting like a Hawk
Loggerhead Shrikes hunt by scanning the ground from elevated perches, then pouncing onto their prey. They also hover-hunt like a kestrel and even hunt on the ground, flashing their wing patches to startle prey out of hiding.
The upper part of the shrike's hooked bill features a pair of built-in projections called "tomial teeth." Like a falcon, the shrike uses these specialized "teeth" to seize and disable vertebrate prey.

Main foods include grasshoppers, beetles, and rodents, some of which are agricultural pests. They also take a wide variety of other prey, including amphibians, reptiles, and birds, as well as road kill and other carrion.

Since they lack a raptor's talons, Loggerhead Shrikes skewer their prey on thorns or barbed wire, or wedge their kills into tight places for easy eating. Caches of prey—called "larders" or "pantries"—provide stores during winter when prey is scarce and in breeding season when energy demands are high. Having a well-provisioned larder may also help a male shrike attract a mate.

Bringing Up Butcherbirds
During courtship, a male shrike performs short flight displays and brings food to the female. The pair build a sturdy nest low in a dense, often thorny, tree or shrub. The male feeds the female while she incubates, sometimes bringing prey cached earlier.

Both parents feed the nestlings, which leave the nest at two to three weeks but continue to be tended by their parents for another three to four weeks. (See a shrike feeding frenzy in this video by ABC's Jim Giocomo.)

Newly fledged shrikes perform exaggerated versions of adult hunting behavior, including rudimentary impaling gestures. They seem to practice their skills by grasping objects in the tip of their bills and repeatedly touching them to a branch or perch, as if trying to get them to stick.

Loggerhead Shrikes have a characteristic behavior when flying from perch to perch, starting high, then flying low to the ground, then up again to a high perch. Because of the white patches in the shrike's wings, they are sometimes confused with Northern Mockingbirds.

Banning the Bomb for Birds
The San Clemente Island subspecies, found on only one island off the California coast, was listed as endangered under the Endangered Species Act in 1977. Beginning in 1996, American Bird Conservancy helped convince the U.S. Navy—which was using part of the island as a bombing range—to expand protective measures for the bird. Thanks to this effort, along with captive breeding, predator control, and other habitat management, the subspecies is steadily recovering.

Land for Loggerhead Shrike
As part of thehttp://www.opjv.org/"> Oaks and Prairies Joint Venture (OPJV), ABC and other Migratory Bird Joint Venture (mbjv.org) partners are working to restore native habitat that will benefit the shrike and other bird species of concern, including the Northern Bobwhite, https://abcbirds.org/bird/painted-bunting/">Painted Bunting, and https://abcbirds.org/bird/black-capped-vireo/">Black-capped Vireo. For example, the Grassland Restoration Incentive Program (GRIP) aims to improve or restore more than 60,000 acres of habitat in focal areas in Texas and Oklahoma.
(Learn more about Loggerhead Shrikes in a https://www.youtube.com/watch?v=eK8sfEQq_EI">video by Texas Fish and Wildlife, featuring ABC's Jim Giocomo.)