On the prowl for the great white owl

Southeast wild

Posted: Friday, April 21, 2000

A bird known across the world for its association with Alaska is rarely glimpsed in Southeast Alaska.

Snowy Owls nest on the Arctic tundra of northern Alaska. The Snowy Owl's plumage (feather) coloration and hunting strategy work best on the open tundra. The mountainous geography and dense, dark spruce trees of Southeast Alaska make it difficult for the Snowy Owl to catch prey, so we hardly see them down here.

The Snowy Owl is the largest avian predator on the Arctic tundra, with a 5-foot wingspan. Snowy Owls show reversed sexual size dimorphism, which means that females are considerably larger than males. Males and females also have different plumage color. Males are nearly pure white, while females are white with black barring and spots on their feathers.

Males and females are monogamous and have different nesting duties. The female is solely responsible for incubating the eggs. Scientists think this is the reason females are bigger and have more black on their feathers. A larger body allows them to incubate more eggs. The dark feathers absorb more sunlight and keeps the female warm when she is sitting on the eggs all day. The male Snowy Owl hunts and brings food back to the female and then the chicks.

The main prey of Snowy Owls are lemmings, a little brownish rodent that spends most of its time in underground tunnels.

Lemming populations are highly cyclic. One year there can be tons of lemmings, then the population crashes, and the following summer lemmings can be very scarce. There are many lemming populations in northern Alaska, and in a single year the different populations may be in different stages. One population may be very high, while the neighboring population has hardly any lemmings at all.

Snowy Owls are nomadic and breed in a different place every year. This allows them to nest wherever lemmings are most abundant.

Snowy Owls begin to arrive on their breeding grounds in northern Alaska around May 20. The snow does not melt until June! The female scratches a hollow in the tundra to protect the eggs from spring snow storms.

The number of eggs laid and chick survival are heavily influenced by lemming abundance. In high lemming years, Snowy Owls may lay as many as 16 eggs, and all the chicks survive. The average clutch size is eight to 10 eggs. The female lays one egg every two days and begins incubating the first egg immediately so it will not freeze.

The chicks hatch out two days apart in the order in which they were laid. If the adult owls cannot find enough food, the older chicks will get the food and the younger chicks will become weak and die. This insures that least some of the young will be healthy and survive. The chicks learn to hunt around 7 weeks old and become completely independent at 9 weeks of age.

In some western and northern game management units in Alaska, Snowy Owls are legally killed for human consumption. There is no closed season and no limit (Units 17, 18, 22, 23, and 26).

One harvest technique is to put a leg hold trap on top of a post in the middle of the flat tundra. The owl lands on the post to allow it better visibility when scanning for prey, and is easily trapped.

Not much is known about the migration patterns of the Snowy Owl. They migrate farther south during years of low lemming abundance, flying as far south as central California, Oklahoma and Alabama! Every winter, between five and 50 Snowy Owls can be seen hunting Norway rats on the plains of Boston International Airport.

It is not known what factors influence this large fluctuation in owl numbers. They arrive in Boston a couple of weeks after leaving their breeding grounds in northern Alaska, and we can only speculate what route they take and what they do in these weeks.

Snowy Owls are very aggressive and frequently attack intruders (wolves, researchers, other birds of prey, etc.) on their breeding territories. Other birds of prey will not nest close to Snowy Owls because the large, white owl will eat the other birds' chicks. Due to its aggressive behavior and its successful survival strategies on the open Arctic tundra, the Snowy Owl has become known as the toughest owl in North America.

The Snowy Owl is the only white owl in North America. Other diagnostic characteristics include a rounded, earless head and yellow eyes. If you do see one in the Southeast region, consider yourself lucky, and call the new Juneau Rare Bird Alert Hotline at 586-2591 to report your success!

Sadie Wright, a Juneau resident, will graduate from the University of Alaska Fairbanks in May with a bachelor of science degree in wildlife biology. She received the Year 2000 Student of the Year Award for her degree program.



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