Bears hibernate. Skunks and deer mice go into torpor (light hibernation) when weather is too cold. But birds? Hummingbirds go into torpor at night to conserve energy. But only one bird hibernates – the Common Poorwill. When weather is really cold, or food isn’t available, the poorwill will hibernate. It can even hibernate while waiting for chicks to hatch!
Edmund Jaeger, an American biologist, was the first to document the extended torpor, or near hibernation, of the common poorwill. He and two of his students found a common poorwill in a canyon wall, cold to the touch with no signs of heartbeat or respiration. While being handled, and hence warmed, the poorwill opened one eye and yawned. This poorwill returned to the same site three years in a row to hibernate. At the opposite end of the temperature spectrum when it is too hot, poorwills will pant and often flutter their throat muscles and release water through their skin.
In size, they are between a robin and a crow. They are a stubby looking bird with a very short neck, mottled brown and gray feathers with a bit of white on the collar. Their coloring gives the impression of dead leaves providing superior camouflage which is why they are more often heard than seen. Their call is a whistled “poor-will”.
They roost on the ground and sometimes in family groups. They may sit in the middle of a gravel road and fly into the headlights of a car like an enormous moth. Flying birds move in moth like patterns with irregular wingbeats to catch moths and other insects in their mouth.
Dinner time is at dusk and just before dawn. They perch low to the ground searching for insects. Then fly out and catch them in their large mouths. Similar to hawks and owls, poorwills cough up pellets of indigestible material from the moths and beetles that make up most of their diet. Grasshoppers and flies are also on the menu.
Common poorwills live in rocky foothills, ranchlands, and suburbs between 1,000- and 7,000-feet elevation.
Where many birds use their beak to preen, poorwills do this with a “pectinated claw” which is a toenail with comb like serrations. This is used to scratch and straighten feathers. This claw is also used to straighten the “rictal bristles” – the stiff hair like feathers around their mouth used to sense prey. These bristles also may aid in moving prey into their mouth.
The poorwill makes a shallow nest on stony ground or in leaf litter usually near a south-facing shrub or rocky outcrop. And it isn’t really a nest in the common sense of a bird nest. It’s just a scrape in the ground. Two eggs are laid and incubated by both parents for 20-21 days. If the nest is disturbed, the parents may move the eggs or the young to another location. Both parents will brood and feed the young regurgitated insects. Nestlings take 20-23 days to fledge. The female will incubate a second clutch while the male continues feeding the first clutch.
The common poorwill will leave in late August to September for the warm winters in Mexico and will return here in the spring.
This is another bird named for Thomas Nuttall, a botanist and zoologist from England. The common poorwill’s proper name is Phalaenoptilus nuttallii. The Nuttall’s Woodpecker and the yellow-billed magpie (Pica nuttalli) are also named for him.
Tri County Wildlife Care, a local nonprofit started in 1994, is dedicated to the rescue and rehabilitation of our native wildlife and helping our community live in balance with wildlife. They envision a world where wildlife and people thrive together. For more information call (209) 283-3245, or visit pawspartners.org.