No one knows more about Whidbey Island’s Northern harrier population than Jack Bettesworth.

Harriers — fixtures in Whidbey Island landscapes — fly low over marshes and fields hunting meadow voles, other small rodents and snakes. Males are grey with black-tipped wings; females sport brown plumage.

For 10 years Bettesworth, a retired pharmacist, has been studying harriers. He began monitoring the birds of prey as part of a Superfund cleanup project at Whidbey Island Naval Air Station.

“I don’t know how to stop,” Bettesworth said, explaining why he continues banding and tracking the nimble birds.

He moves from Seattle to Coupeville each summer to band, tag and track the small raptors with the help of volunteers. This year, they found 28 nests scattered from Useless Bay to Ault Field.

Bettesworth and the volunteers spend hours behind binoculars and spotting scopes watching courtship displays in early spring. They watch harriers build their nests on the ground and note when adults begin taking prey to the nests. After that, they count the days until the young raptors are big enough to be banded.

Finding the nests

From the hours of watching, the group knows almost to the foot where the nest is located, said Bob Merrick, one of the volunteers. Volunteers use radios and cell phones to guide Bettesworth through thick brush and over uneven ground.

Great care is taken with the young birds. Everyone looks for red-tailed hawks and eagles that prey on harriers. Bettesworth carefully secures the wings with a soft, stretchy veterinary wrap before moving out to what he calls the “processing area” to quickly weigh, measure, leg-band and wing-tag the birds.

Each tag has a discrete code to identify exactly which nest the bird came from. The wing tags can easily be seen with binoculars, making field identification quick.

The wing tags have given the researchers the most information about harriers on Whidbey Island.

The birds don’t mate for life as eagles do; males can take multiple mates each season. These birds are nomadic — each year they select new nest sites. And each year the young scatter all over the island.

“They are fascinating. Each year we see something new,” Bettesworth said.

“It’s fun to see which birds from which nests turn up where on the island,” Pat Cozine, another volunteer, said.

One male harrier has carried prey from Au Sable Institute south of Coupeville to a nest on Crescent Harbor, a six mile trip, Merrick said.

Switching menus

The group has seen the birds adapt subtly to environmental changes. In 2002, the meadow vole population crashed. Voles are the harriers’ main prey. Last year, harriers took more small birds, bunnies and even snakes to compensate for the scarcity of voles.

The birds select varied nesting sites: Some nest not too far from runways on Whidbey Island Naval Air Station’s Ault Field; other spots are deep in marshes at Crescent Harbor and on Useless Bay. Where they nest makes a huge difference in the likelihood of a clutch of eggs hatching.

At least one nest this year was destroyed when a hay field was mowed. Nests in areas that have never been disturbed have the best chance of being successful.

“Harriers need places to nest as much as they need good places to hunt,” Bettesworth said.

Habitat destruction is the biggest challenge these birds face. Bettesworth and Merrick can cite several examples. If fields around Crescent Harbor and the marsh were developed, harriers would lose critical habitat.

Bettesworth doesn’t waste time, he wants to get the birds back in their nest as fast as possible. To cover his scent from coyotes, he will drop mothballs on his way out. He wants these birds to mature so he and others can track their lives for several years.