Pennsylvania Game News - December 2009 - 64

Lock, Stock & Barrel The Shooters’ Corner By Jim Romanelli By Don Lewis Complex Calls OFTEN HEAR it while snowshoeing on my woods roads: the buzzy, repetitive chick-a-dee-dee calls of black-capped chickadees. In winter these small, spunky birds join up in flocks of six to ten. When I meet one, the birds are usually foraging in and near trees, eating seeds, berries, and spider and insect eggs. Black-capped chickadees are found from Nova Scotia to Alaska and south to West Virginia and northern California. Chickadees don’t migrate; they cope with winter. At night the birds roost separately, amid the sheltering boughs of conifers and in tree cavities. When it gets really cold, a sleeping chickadee’s temperature drops from a normal 108 degrees Fahrenheit to about 50 degrees, putting the bird into a state of regulated hypothermia to save energy. They slowly lose weight throughout the night as their bodies burn fat to stay alive. The next day they must replace the fat through their feeding. The familiar chick-a-dee-dee call helps hold the flock together as the birds move around in a territory of 20 or more acres. The call can also be used to sound an alarm when a predator is spotted, and it can trigger “mobbing” behavior — when the chickadees, and other birds who hear the ruckus, flit around near a predator and advertise its presence by scolding it. Recent studies show that chickadees’ calls convey a lot of information, including a predator’s type and size and how much of a threat it represents. In Montana, biologists spent many hours observing chickadees in a large, outdoor semi-natural aviary. One by one, they put predators inside the aviary: 15 different species of birds and mammals. During each predator encounter, the biologists recorded the chickadees’ behavior and calls. When they played back the vocalizations at a slow speed, they learned that the number and type of syllables and their acoustical features varied, depending on the predator. The more dee-dees that were given, the more likely the predator was of a species that kills and eats chickadees. The chickadees were only mildly alarmed by a great horned owl, a large raptor that generally seeks out larger prey. But when smaller raptors were put into the aviary — saw-whet owl, pygmy owl, merlin and kestrel — the chickadees fired off calls with more and shorter dee syllables. Cooper’s hawks and peregrine falcons, relatively large raptors that, despite their considerable size, also eat chickadees, triggered numerous dee calls. The biologists concluded that the chickadees were not reacting simply to a predator’s size, but that they recognized certain raptors as dangerous. The biologists tested their observations by playing back recordings of chickadees confronting both dangerous and not-so-dangerous predators. Sure enough, the chickadees responded most vigorously to the “high-threat” mobbing calls. Perhaps it should not surprise us that chickadees are so sophisticated in their communication. The research raises a tantalizing question: How many other comCorrection: Deputy Edward Page, featured in plex systems of communication still November, was reported as the Southeast await our comprehension? Region Outstanding Deputy of the Year. Actually, Officer Page is the Northeast Region Outstanding Deputy of the Year. I GAME NEWS

Pennsylvania Game News - December 2009

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