What is a flammulated owl?

Flammulated owls nest throughout the American west, mostly in evergreen forests. This type of owl so small, you could hold one in the palm of your hand.

If you could see one of these owls up close, you’d notice rusty-colored feathers on its face and shoulders. The feathers make a pattern like candle flames – hence the name “flammulated owl.” But you’re not likely to spot a this owl – its feathers are the color of tree bark.

What do they eat? Flammulated owls feed at night. They catch moths in midair.

Large owls such as the barred owl and great horned owl have booming, hooting calls that are unmistakable. The flammulated owl is different. Its call is more like a “coo” than a “hoot.”

“A lot of the people I take out at night are not even aware that the owl is calling until I point out what it is they should be listening for,” said Brian Linkhart of Colorado College. He’s been studying flammulated owls for two decades. He goes out into the forest at night and imitates the owls to attract them. In the past he has fitted owls with small radio transmitters and tracked them to determine the extent of their territories, find out where they spend the most time feeding, and locate their nest sites. By checking the nests regularly throughout the breeding season and putting identifying bands on young owls, Linkhart has been able to gather information about nest productivity: how many eggs are laid, how many hatch, and how many young birds survive to “fledge,” or leave the nest.

Flammulated owls lay their eggs in the tree cavities hacked out by small woodpeckers. In stands of mature ponderosa pine and Douglas fir, the owls seem to raise more young.

That’s important, because these owls don’t reproduce very fast. Other small owls may lay as many as seven eggs at a time – but two or three seems to be the limit for flammulated owls. Many of the big Ponderosa pines and Douglas firs have already been logged off – so there’s not much good owl habitat left. What’s more, in many national forests, the policy has been to prevent fires. This may leave them too dense to be good owl habitat.

Linkhart says flammulated owls have the best success raising their young in open forests, with large trees that are spaced far apart. “It looks like the primary things the owls use to tell if a territory is of good quality are the relative sizes of the trees, the relative distance between the trees, and whether the trees have cavities,” he says. Scientists say flammulated owls can be especially sensitive to habitat disruptions.

In the spring, a male owl claims a breeding territory of about 40 acres. A male that manages to claim a good territory will return to it year after year; the oldest male in Linkhart’s study was at least 13 years old.

Only half of the male owls in a given area will attract a mate and raise young in any given year. That seems to suggest that there are not enough females to go around, perhaps because females suffer a higher mortality rate than males. After a long migration north in the spring from Central America, a female lays a clutch of eggs that equals half her total body weight. Linkhart thinks the stress of nesting may take its toll on females.

Our thanks to:
Brian Linkhart
Associate Professor of Biology
Colorado College
Colorado Springs, Colorado

November 5, 2009

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