Predator Birdie

The loggerhead shrike might appear innocuous, but it’s ready to pounce.

It sounds like a creepy image from a horror film: a dead mouse, lizard, or other small creature skewered on a thorn or a twist of barbed wire. But for a birder, it’s the signature sign of an elusive and diminutive—but deadly—songbird.

“Finding a mouse or bug impaled on barbed wire, thorn, or stick is an excellent way to know that loggerhead shrikes are in the area,” says Sergio Harding, nongame bird conservation biologist for the Virginia Department of Wildlife Resources.

Found only in North America, the loggerhead shrike is a bird a little smaller than a robin, with gray and white markings and a black mask. Perched on a fencepost or the branch of a shrub, it might appear as innocuous as any other songbird. But from that perch it casts a predator’s eyes on the ground below, ready to pounce. The shrike will take an insect, but also small mammals, frogs, snakes, even other birds, with a quick paralyzing bite to the neck, often followed by a brutal shaking that finishes the job. Some biologists in Texas once observed one taking out a Northern cardinal with only a brief struggle. “A necropsy revealed that the cardinal’s neck was broken at the base of the skull,” the researchers noted.

But then a dilemma. Blessed with a raptor’s spirit—and its flesh-tearing hooked bill— the loggerhead shrike nevertheless is endowed with a songbird’s delicate perching feet. Lacking the powerful talons to clutch its prey firmly while consuming it, the shrike has an ingenious, if somewhat gruesome, alternative strategy: impaling the prey on a sharp protuberance to hold it in place. The birds will sometimes even build up a cache of impaled meats, a kind of kabob buffet.

For this dinner-on-a-skewer practice, the shrike has earned the grim nickname “butcherbird.”

Virginia plays host to year-round, breeding, and wintering populations of shrikes, whose preferred habitat here is open pastures, ideally with short grass and bare ground to make prey more visible, and with shrubs, trees, fences, and powerlines for perching and watching for a meal. Although the birds can occasionally be seen elsewhere in the state, their stronghold is western Virginia, says Harding.

Across North America, however, populations of loggerhead shrikes have been in decline for decades—the birds are believed to be extirpated in the northeastern U.S. north of Virginia, Harding says. The reasons for this decline, though, are not clear. “A lot of the research that has been done on shrikes had been conducted somewhat piecemeal, without a lot of communication, and so no smoking gun has emerged as a cause of population declines,” Harding explains. To better study and understand population and migratory dynamics of the bird, therefore, a coordinated Loggerhead Shrike Working Group was formed in 2013, with the Virginia Department of Wildlife Resources as one of the group’s founding members. “The idea of the group is that instead of isolated research, we are trying to work in a collaborative and coordinated fashion—sharing information, participating in multi-state projects, and helping to direct one another’s research.”

One part of the research has been a banding-and-monitoring project; captured shrikes are fitted with a series of small colored bands, with each bird’s bands configured in a unique pattern. One shrike Harding banded in Virginia eventually showed up in Ontario, which hosts a small migratory population of the birds. Others have turned up in “beautiful photographs” on the citizen-science site eBird, a resource which, Harding notes, is becoming “an incredible treasure trove of data” for bird researchers.

Finding and trapping the birds to band them, however, is something of a challenge. “Shrikes can be very difficult to detect,” says Harding.  

For one thing, “they vocalize a lot less frequently than your average songbird,” says Harding, so you can’t use your ear to locate them as easily as you can other songbirds. For another thing, loggerhead shrikes look enough like mockingbirds that it can be possible to confuse them. “A lot of times you get out to these pastures where they share space with mockingbirds, and you get all excited that you saw a shrike,” only to realize on closer look that it’s a mockingbird.

 Shrikes have a long breeding season, beginning to nest in mid-April in Virginia, and they are also “double-breeders” that can have more than one successful nest in a season. The chicks fledge within about three weeks of hatching. Then, according to the Cornell Lab of Ornithology’s “All About Birds” website, young fledglings take a little while to get the hang of the family nickname, practicing “rudimentary impaling gestures” before they’re ready to go the full Vlad.

“It’s that impalement,” says Harding, “that makes them unique among songbirds.”

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