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Science File | IN BRIEF

High Testosterone Giving Warblers an Edge

August 28, 2004|From Times Staff and Wire Reports

Hormone-fueled songbirds are steadily forcing out a rival species in Northwestern fir forests and threatening the more timid warblers with extinction, U.S. researchers said Tuesday.

They said high levels of testosterone they measured in the birds may explain the aggressiveness of the Townsend's warbler, which has been displacing its sister species, the hermit warbler, in Alaska, British Columbia and Washington.

The Townsend males seem to be stealing away hermit warbler females, the University of Washington team wrote in the journal Biology Letters.

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