Pygmy owl: Bite much bigger than its beak

Posted: Friday, February 19, 2010

The northern pygmy owl is not the smallest owl in North America; the tiny elf owl of our southern deserts merits that distinction. But our northern pygmy owl is indeed small, measuring only six or seven inches in overall length, including the tail. Perched on a tree branch, a pygmy owl stands maybe five inches tall. They only weigh about 70 grams (or 2.5 ounces).

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Photo By Bob Armstrong
Photo By Bob Armstrong

Pygmy owls are cavity nesters, often using old woodpecker holes. The female incubates the clutch of two to seven eggs, sitting on them for about four weeks. Then, the chicks stay in the nest for a little more than three weeks, but are still fed by their parents after they leave the nest.

While the female is tending the eggs and small chicks, the male brings prey to the nest. Male owls in breeding season commonly story prey in the nest, sometimes building up a cache of numerous prey items. The cache may be started during the courtship period but often continues through the nestling period. A sitting female owl may be surrounded by the corpses of a dozen (or more) prey, as she incubates the eggs or broods the nestlings.

Pygmy owls are little bundles of ferocity. They are known to attack prey more than twice their own size. Their principal prey is birds, but they also eat small mammals and insects. They even extract nestlings of other cavity-nesters, such as wrens and woodpeckers, from their nests. Unlike many owls, these are daytime hunters and rely mainly on vision (not hearing) for capturing prey.

The northern pygmy owl ranges from Southeast Alaska down into Mexico, where there are two other, similar, species. Still others live in Africa, Eurasia and South America. In the Chilean rainforest where I worked for many seasons, the southern pygmy owl is called the chuncho (or, because Chileans seem to love diminutives, the chunchito). It is a fearsome predator. One day we were mist-netting birds, so we could band them, and we caught several songbirds. Right next to one of those songbirds was a chuncho, which had got netted as it attacked the entangled songbird.

I extracted the owl from the net so we could weigh and measure it. Then I held it upright so we could take its picture. Somehow, that fierce little thing twisted around and got its talons into my hand, so the photo showed my perforated hand, well decorated with nice fresh blood running down my wrist, as well as the defiant owl. Then I released it.

Undaunted, it flew straightaway after another songbird that was caught in the very next mist-net.

Here in our forests, the northern pygmy owl is often hard to see. It lurks in the conifer foliage, awaiting its chance for attack. If it is discovered by songbirds in the area, they may mob it, screeching and swooping near the stationary owl. Sometimes the mobbing activity helps birdwatchers find the owl.

Pygmy owls of the Americas have distinctive and conspicuous eyespots on the back of the head that appear as big black marks outlined in white. Some enterprising experimenters made wooden owl models with and without the eyespots, in order to study the effect of the fake eyes on mobbing songbirds. They attracted the attention of local songbirds by playing tape-recorded mobbing calls and pygmy owl calls. They found that the mobsters approached the model without eyespots both from the front and the back, but the eyespot model was approached mainly from the front-the big eyespots were avoided.

What might be the advantage of the eyespots for their owners? The researchers suggested that, by redirecting mobbing birds to the front of the owl, the eyespots may reduce the risk of getting hit from behind and even give the beleaguered owl a chance of grabbing one of the pestering songbirds.

• Mary F. Willson is a retired professor of ecology.

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