Geography Reference
In-Depth Information
These species breed in western Washington but overwinter in western Mex-
ico, Central America, and South America. Many migrants are on the decline
as they face challenges in two worlds as well as along the migratory route that
connects them. They avoid development because it removes understory nest-
ing cover used by the thrush, l ycatcher, and Wilson's warbler and the upper
canopy used by the other warblers. Similarly, resident Pacii c wrens and golden-
crowned kinglets require native groundcover and canopy cover, respectively,
and so, too, avoid development. The last two avoiders are residents that
require dead trees. The hairy woodpecker drills its nests and nighttime roosts
in dead trees that average ten inches in diameter. The brown creeper is a tiny
bird that hitches up tree trunks probing the bark with a long, narrow, decurved
beak in search of spiders and insects. It builds a soft nest out of lichen, moss,
i ne rootlets, and hair behind l akes of peeling bark that develop in the i rst
few years after a tree dies. Dead trees, or “snags,” are critical resources for many
birds, but construction crews and homeowners concerned with safety quickly
remove them. That many small snags remain in our forests may explain why
both creeper and woodpecker populations are faring better than the other de-
velopment avoiders across the West.
The tenure of some avoiders within recent developments may be short-
lived. This possibility haunted Cara Ianni, a young educator from the Seattle
area who believed it was important to teach from experience. Seeking expo-
sure to conservation biology, Cara began her graduate research in 2003 to
determine how birds fared as Seattle's subdivisions aged. She surveyed birds
in thirty-i ve neighborhoods that ranged from i ve to one hundred years old.
She quickly saw that older neighborhoods lost their forest-dependent birds.
Not a single Townsend's warbler or hairy woodpecker could be found in any
of the seven neighborhoods that were seventy or more years old. Black-throated
gray warblers, Swainson's thrushes, and Pacii c-slope l ycatchers were found
in only one old site. Our other avoiders remained, but were rare, in Seattle's
oldest neighborhoods.
 
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