A few years ago I documented evidence of breeding Red-breasted Nuthatch
(Sitta canadensis) and Golden-crowned Kinglet (Regulus satrapa) in the
southern Appalachians of Georgia. This population had been previously
undetected because they did not vocalize much and perhaps because few
birders had been in that area of mature white pine and hemlock after
migration. Now that I have been back in Seattle for a few years, I have an
unquantitated impression that these two species do in fact vocalize a lot
more in the NW USA than at the edge of their range in north Georgia.
Although it might make sense, I could only find a few papers arguing that
at low densities, such as at the edge of their range, species might tend
to vocalize less than at higher population densities, with a lot of singing
rivals nearby. Does anyone have any similar or counter impressions?
Oberle, M.W. and J.C. Haney. Possible breeding range extensions of northern
forest birds in northeast Georgia. The Oriole. 1997. 62(3-4):35-44.
Rappole, J.H., W. J. McShea, and J. Vega-Rivera. 1993. Evaluation of two
survey methods in upland avian breeding communities. J Field Ornith. 64:55-=
70.
Mark Oberle
2006 23 Ave. East
Seattle, WA 98112-2936
Tel: 206-324-3844
www.mindspring.com/~oberle/PRbirds.htm
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