Wrentits in northern Willamette Valley

This spring and summer there have been several scattered reports of Wrentits in NW Oregon outside their historic range. Could the sightings and heard-only reports be correct? Possibly. On the other hand some might just be weather balloons.

Reports have come from North Portland, Sauvie Island Wildlife Management Area, Hagg Lake, and Tualatin River National Wildlife Refuge. Thus far, all these reports from well-birded areas are unverified--descriptions are incomplete and others can't find them the same or next day. That's a problem for me. I'll tell you why.

Wrentits are sedentary to the extreme. Their home ranges are a tiny 2-1/2 acres--a few hundred feet across. Pairs of birds mate for life and are never far apart (Terres, 1980. The Audubon Encyclopedia of North American Birds). Both sexes sing throughout the year--a very loud and unique bouncing ball whistled trill. On the rare occasions when birds have been found pioneering new areas they are rather easily and repeatably detected.

The range of Wrentit in Oregon hasn't changed all that much in 200 years. Historically, they were found along the immediate coastline in salal bushes under the scrubby shore (lodgepole) pine, from California to the Columbia River. They have never crossed the Columbia into the state of Washington, even though regular on the Oregon side of the mouth of the river. In winter they sometimes can be found a few miles inland into clearcuts. They also occur in the SW area of the state near Medford in low-elevation chaparral of the Rogue Valley, and in low numbers into the Klamath Basin.

Recently (the past 50 years or so), their inland population has inched northward through the Umpqua Valley to the eastern edges of the southern Willamette Valley in Lane County. A population has also crawled northward on the western edge of the Willamette Valley, from Finely NWR near Corvallis in the 1970's to Grand Ronde of Yamhill County.

There are three known isolated outposts north and east of this range. Birds were detected in the late 1990's near Lebanon. Birds this century colonized the Sandy River delta near Gresham. Birds recently arrived at Minto Browns Island Park in Salem. Especially is this last location hard to fathom. Birds either hopped across miles of city streets or somehow crossed the Willamette River. This from a species that refuses to come out of cover and is loathe to cross a single lane dirt road!

Of course, birds had to get to these new outposts by crossing miles of unsuitable and even dangerous (for a Wrentit) habitat. Thus it is possible that some of this year's out-of-range reports may be correct. I take comfort in my present skepticism, knowing that if birds really are present at these new locations they won't stay undetected for long.

Wrentit

Wrentit, near Lincoln City, Oregon, 30 July 2011 by Greg Gillson.

 

The Wrentit is a small little mouse of a bird found in coastal scrub and chaparral from extreme northern Baja California Norte to the mouth of the Columbia River in Oregon. It stays hidden and fly-hops from branch to branch, rarely crossing an opening. If it wasn't for its bouncing whistled song and quiet rattling call, no one might ever know it existed!

In the Pacific NW it is only found in Oregon, along the entire coast, inland in clearcuts nearly to the summit of the Coast Range. It is found in SW Oregon inland in the California-type vegetation habitats of the Rogue Valley and Klamath Mountains to Klamath Falls.

In the past century it has slowly expanded its range. It has crawled its way northward in western Oregon to the Umpqua and edges of the southern Willamette Valley. In the past decade or two it has colonized new locations along the edges of both the eastern and western edges of the mid-Willamette Valley. Imagine everyone's surprise when they showed up in the last year at the mouth of the Sandy River into the Columbia east of Portland!

Will it ever cross the Columbia into Washington State? Well, it has been common in Astoria for at least 200 years and hasn't crossed the River, nor even expanded upriver toward Portland. The recent birds in Portland evidently came from the south, not the west.

The bird is not closely related to any other bird in the New World. At present, it is listed with the Old World Babblers--the only New World representative in that group.