Geography Reference
In-Depth Information
the Australian raven. The Bewick's wren might be acting similarly in the sub-
urbs around Seattle, so Laura dug in deeper and unraveled the interaction be-
tween Bewick's and Pacii c wrens for her graduate thesis.
She quickly coni rmed that as the thick native understory that is so im-
portant to Pacii c wrens for nesting, feeding, and shelter is removed, their
numbers plummet. In our developing subdivisions Pacii c wren abundance is
halved during the i rst i ve years of construction. But rather than leveling
of after forest clearing occurred, Pacii c wren numbers continued their
downward slide—another 40 percent were lost during the next i ve years.
Throughout this decline, Bewick's wrens increased threefold, and it was their
aggressive actions that contributed to the free fall of Pacii c wrens and espe-
cially to their virtual absence from older neighborhoods. Although both typi-
cally use dif erent sorts of habitat—Pacii c wrens seek cool, dense evergreen
forests and Bewick's wrens prefer shrubby clearings—in new subdivisions Be-
wick's wrens creep into the forest and take up residence in typical Pacii c wren
habitat. As Bewick's wrens defend their new digs, they evict resident Pacii c
wrens. Pacii c wrens are forced from territories where they likely raised young
the previous year and from which their ancestors raised wrens for thousands
of years. Most of the evictions are via vocal summons, but occasionally feath-
ers l y as the larger Bewick's wrens give chase to the mousy Pacii c wrens.
Suddenly my childhood question seemed more urgent. Not only were
animals such as Pacii c wrens forced out of their homes by the clearing that
followed survey stakes, but also those that remained may still be pushed along
by other species more adept at surviving in our gardens and parks. I was left
wondering where the wrens went. Did they die, or did they move? Kara Whit-
taker left the marshes of her native Wisconsin to help answer the question as
part of her doctoral research.
Pacii c wrens are about the size of a thumb, the color of dirt, and rarely
venture more than about three feet above the earth's surface. How in the heck
was Kara going to track them through the temperate rainforest? Pacii c wrens
