A recent range-wide inventory suggests the known population of the Oregon Vesper Sparrow could be even smaller than scientists previously believed.

The new research confirms that the sparrow's population is not larger — and likely smaller — than earlier estimates of approximately 2,100 birds, according to Bob Altman, ABC's Northern Pacific Conservation Officer and the study's lead.

The Oregon Vesper Sparrow, once common in certain areas of the west, is known to have a small population. New research suggests the bird's numbers could be even smaller than scientists believed. Photo: Klamath Bird Observatory.

The Oregon Vesper Sparrow is a subspecies of the Vesper Sparrow. It was once a common bird in western grasslands and savannas of southwestern British Columbia, western Washington and Oregon; and in a small portion of northwestern California.

The U.S. Fish and Wildlife Service's multi-state grant program supported the extensive survey, which covered nearly all the bird's range. Researchers targeted places where Oregon Vesper Sparrows had recently been detected, as well as significant areas of potential habitat both close to and far away from known populations. Still, scientists detected sparrows at only 13 percent of the approximately 700 roadside point count stations.

The sparrow's dwindling presence in the Puget Lowlands and Willamette Valley are of particular concern: Fewer than 500 birds remain in each ecoregion. Meanwhile, the sparrow's stronghold appears to be light to moderately grazed rolling hills and pasturelands in the Umpqua Valley of southwestern Oregon, where large ranches are common.

ABC's next step will be to complete a conservation status assessment within the next year to recommend conservation actions, Altman said. “It may even be necessary to petition that this bird receive federal protection under the Endangered Species Act," he said.