However, the 95% CRI on each time series of population density suggests at least the potential for stable dynamics in every species except the Olive-sided Flycatcher.
However, we saw no difference in the number or direction of trends when comparing migrant with resident species: for example, declining species were split between residents like Hutton's Vireo and migrants like Olive-sided Flycatcher, and in this case the migrant exhibited one of the strongest apparent responses to local precipitation-as-snow.
Early in the past century seven species were found nearly every spring near Urbana but more than 40 years later they were recorded at Charleston in less than half the 23 years: Olive-sided Flycatcher
, Yellow-bellied Flycatcher (5 years), Bewick's Wren (8 years and none after 1984), Winter Wren, Loggerhead Shrike, Black-throated Blue Warbler (3 years) and Pine Warbler.
The olive-sided flycatcher
, which is in the same genus as the pewees, says Quick, free beer!
In the past quarter century, the North American Breeding Bird Survey--the main source for bird population trends--has documented a 51 percent decline in the cerulean warbler, a 48 percent decline in the olive-sided flycatcher
, a 41 percent drop in the wood thrush and a 34 percent drop in the Eastern wood-pewee.
Based on the ANOVA, 5 species (Gray Jay, Brown Creeper, Winter Wren, Varied Thrush, and Chestnut-backed Chickadee) were strongly affected by changes in habitat area (P[greater than or equal to]0.007), 5 species (Evening Grosbeak, Hammond's Flycatcher, Pileated Woodpeecker, Western Wood-Pewee, and Red-breasted Nuthatch) were moderately affected (0.011 [greater than or equal to] P [greater than or equal to] 0.092), and 5 species (Red Crossbill, Red-breasted Sapsucker, Western Tanager, Olive-sided Flycatcher, and Red-tailed Hawk) were virtually unaffected (P[less than or equal to]0.212).
-- Based on the ANOVA, only 2 of 15 species (Olive-sided Flycatcher and Western Wood-Pewee) associated with late-seral forest were affected (P [greater than or equal to] 0.043) by habitat configuration when evaluated as a simple dichtomous variable nested within four levels of habitat area (20, 40, 60, and 80% of landscape area in late-seral forest); both species were more abundant in the more fragmented landscapes.
Four of the bird species I detected, (Pileated Woodpecker, Olive-sided Flycatcher
, Willow Flycatcher, and White-breasted Nuthatch) were listed as vulnerable by the Oregon Department of Fish and Wildlife (Table 1).
"The majority of the preserved open space provides a contiguous habitat corridor for wildlife, including those species that have a state-sensitive listing, such as the pileated woodpecker, red-legged frog, olive-sided flycatcher
and Pacific western big-eared bat," she said.
Many of our neotropical migrant birds, such as mountain bluebirds and olive-sided flycatchers
, are habitat specialists that thrive in these early successional conditions.
The black-backed woodpecker, for example, has evolved protective coloration that mimics the trunks of charred trees, and species such as olive-sided flycatchers
use snags left by wildfires as perch sites.