Tuesday, January 18, 2011

THE HAWK OF THE OWLS

When you first encounter a Northern Hawk Owl (Surnia ulula), you will understand why it has two different types of raptors in its name. Clearly an owl because of that big head and forward-facing eyes, nevertheless it has the rakish look of a hawk about it, with long tail, rapid flight, and – of course – diurnal habits.

One of these birds spent the winter of 2010-2011 on Westham Island in southwestern British Columbia, delighting birders and nature photographers by the hundreds. Because of their open perching habits and tameness, Hawk Owls are readily detected where they occur, so it is likely that at least some of the few individuals that make it to peripheral wintering areas are found as observers scrutinize the winter landscape. In my case, it was a wonderful way to start the year - and on a beautiful sunny day!

In the Pacific Northwest, we don’t get veritable invasions in winter, with dozens of Hawk Owls showing up like they do in the Great Lakes region. Nevertheless, at least a few birds make it down to Washington in most winters, and with increasing knowledge of where to look for them, more have been seen in recent years. Breeding has been confirmed at Manning Provincial Park, just north of the border in British Columbia, and suspected at Harts Pass in Washington.

Hawk Owls perch, usually at the very top of a tree or other conspicuous perch (often on utility wires in this day and age), and survey the surrounding semiopen landscape for their prey. Their primary prey is voles, but they are willing to take anything they can subdue from a long list of mammals up to the size of hares and birds up to the size of grouse.

Hawk Owls are not modified like many other owls for auditory hunting. Their two ears are symmetrical, and they don’t have a well-developed facial disk. They must have good hearing, however, as they are occasionally seen to plunge into snow to capture a vole. With long tail and short, rounded wings, they hunt somewhat like accipiter hawks, detecting prey visually and dropping from a perch to move at high speed with rapid wing beats. Most prey is captured at fairly close range, but their distant vision is excellent.

There are other diurnal owls. Most pygmy-owls hunt during the day, small birds their primary prey. Snowy Owls and Burrowing Owls are conspicuous features of open landscapes, although both hunt at night as well. Short-eared Owls can be seen during the day, but much of their hunting is at dusk. The same is true for Great Gray Owls. Hawk Owls, conspicuous on their perches all day long, also tend to hunt more in the afternoon, so hunting in dim light seems to be hardwired in owls.

Bear in mind that owls of the Far North must be able to hunt both day and night, as the days are so long in summer, the nights so long in winter. Fortunately for them, voles are active day and night.

Like many other owls, Hawk Owls nest in natural cavities, for example at the hollow tops of broken-off snags, and holes abandoned by woodpeckers. Their clutch size varies from 3-13 eggs, with a mean of about 7. It is a large and variable clutch size, as is the case with several owl species that seem to depend on voles and lemmings for their reproductive success.

Keep your eyes peeled for the owl that acts like a hawk!

Dennis Paulson

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