Owls of Iowa: Snowy owl

Snowy owls are not constant winter guests in Iowa.

Their behavior is known as irruptive, which means they might appear in some winters and not in others. That means that when a snowy owl is spotted, it's a big deal.

Let's check out some reasons why snowy owls are such a neat bird.

1. Large and in-charge

The snowy owl is actually the largest North American owl species, weighing in up to 6.5 pounds and growing up to almost 28 inches in length. The great horned owl is just a touch smaller at 5.5 pounds and almost 24 inches long. The great gray owl isn't found in Iowa, but it is America's tallest owl, growing up 33.1 inches in length. The great gray owl only weighs about 3.5 pounds, though.

The reason that snowy owls are so heavy is their thick feathers that insulate them from the Arctic cold. They even have dense leg feathers, making them look quite squatty when sitting.

2. Loving lemmings

Snowy owls spend their summers in the Arctic hunting lemmings, ptarmigan and other prey in the 24-hour daylight. Their primary food source is lemmings, and these rodents have cyclical population patterns, spiking every five to 10 years. When their populations spike, the numbers of snowy owls rise as well.

3. The odd duck of owls

Snowy owls are easier to spot than other owls because they are diurnal — meaning, of the day. They hunt during daylight hours, because in their breeding grounds in the Arctic it’s always daylight. In Iowa, that makes them easier to spot as they sit near the ground, looking for prey.

They will also stay in the same spot for a long time, often hours, as they look and listen for prey.

4. Mostly white

We think of snowy owls as white birds, which they are. However, they aren't completely white. Males have dark brown stripes when young and get whiter as they get older. Females keep dark markings throughout their lives. The whitest birds are always male, and the darkest snowy owls are always female. In the middle ground, there is some overlap of male and female.

5. They're back

The snowy owl that you saw in the area last year might be the same snowy owl that you spot this year. Some banded snowy owls have been found to migrate to the same wintering site year after year.

6. Branching out

Unlike osprey, which usually return to a breeding ground about 50 miles from the place of fledging, snowy owls often branch out far from the place they hatch. One study found that young from a single nest in the Canadian Arctic spread out to Hudson Bay, southeastern Ontario and eastern Russia.

7. Wide open spaces

Snowy owls are used to their wide-open breeding grounds in the Arctic, and they tend to stick to those same types of areas in their wintering grounds as well. In Iowa, you might spot them around airports or agricultural fields where they sit on the ground or perch on short structures like fence posts to hunt. One might sit in the same spot for hours, usually their bionic vision and hearing to wait for prey.