Friday, July 3, 2015

Home Again: Clay-colored Sparrow

A light rain was just starting to taper off as we crashed through the brush. The spicy fragrance of crushed sweet fern tickled our noses pleasantly. Birds sang all around us. Pushing through the clumps of head-high, stump-spouting scrub oak and red maple, we stepped carefully over the sooty remains of trees. Coming up on a long, narrow open area, a tall metal pole appeared out of nowhere – like finding the lamp-post in Narnia.

With a little squinting, we soon noticed some filmy, black netting strung from the pole, 30 feet through the open area, and hitched to a matching pole. A few raindrops sparkled on the web. Here, our small group of Wisconsin Master Naturalist students gathered around Jim Bryce, a retired biologist with the USDA Forest Service and National Park Service, and long-time bird bander.

Briefly, Jim explained how the mist net works. The fine black threads are nearly invisible, and they are strung to form long, floppy pockets. When an unsuspecting bird flies into the net, it drops into a pocket, and gets tangled in the net. Then a bander can carefully extricate the bird for processing.

As he talked, we noticed a flutter at the far end of the net. “Looks like we got one,” observed Jim, as he pushed toward it through the brush. And then, with considerably more excitement in his voice, “It already has a band! This must be the same clay-colored sparrow we caught last year!”

Returns – re-catching a previously banded bird at least three months later – are rare in the banding world, but they provide a wealth of information. From these recaptured birds, scientists have learned about the incredible 24,000 mile round-trip migration that Arctic terns complete each year; the wintering habitat of Bicknell’s thrushes; and the maximum known age for a wild bald eagle (32 years, 10 months). However, only about 1% of small birds are ever caught again.

“This is the perfect habitat for clay-colored sparrows,” Jim explained as he gently untangled the banded sparrow’s feet, feathers, and beak from the net. The Forest Service has been managing this area as open brushland, using fire to keep out the trees and provide the dense, shrubby, cover that many species need. That’s why we were stepping over burned logs and pushing through thickets of fire-dependent plants on the way here.

Clay-colored sparrows need this brushy habitat. Females build their nests in the lower branches of impenetrable thickets, preferring a spot with as little light penetration as possible for protection from predators. A low nest is good for the fledging chicks, too, since they hop to the ground before they can fly, and hide in dense thickets nearby while their parents feed them for a few more days. Unlike most other species, adult clay-colored sparrows forage outside of their nesting territory throughout the whole process. This leaves more food available near the nest for the flightless chicks.

Mostly due to a loss of their preferred brushy habitat, clay-colored sparrows have been in a slow decline over the past 40 years. That is one reason why the Forest Service’s management plan here in the Moquah Barrens on the Bayfield Peninsula is so important. Our returning sparrow is proof that they are doing a good job. Jim’s annual bird banding here will help to quantify their success.

When we finally got the sparrow extricated from the net and back to the processing table, we confirmed that he was in fact the same bird -- band # 53262 -- we caught last year in that same place. Male clay-colored sparrows return to the same territory year after year, but pairs do not mate for life. Instead, each year during migration the females find a new mate and follow him home.

The government will be following him now, too. At the end of each year, Jim reports all of his banding data to the USGS Bird Banding Laboratory. They’ll make note of this return. The Forest Service will be interested in that information, too, since it helps to validate their management plan. If we or someone else catches our little friend for a third time, they can report it to the laboratory, too, and we’ll gain even more information.

Jim spent a few minutes with our bird, measuring his wing length, tail length, and weight. Once the data was collected, a student placed our little brown-and-white streaked friend gently on the ground. We held our collective breath for a second as he got his bearings, and then with a flutter he was gone.

As we turned back to the table to process more birds, we heard the characteristic bzz-bzz-bzz song of a clay-colored sparrow, claiming this beautiful brushland as home.

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