>SIGNIFICANT DIFFERENCES IN CALL STRUCTURE AMONG PACIFIC NORTHWEST
>CROW POPULATIONS
>
>James C. Ha & Samuel J. Ha
>Psychology Department, University of Washington, Seattle WA 98195
>Biology Department, Millersville University, Millersville PA 17551
>
>ABSTRACT
> Vocalizations are frequently used in the identification of
>Pacific Northwest crows (American Crow, Corvus brachyrhynchos, and
>Northwestern Crow, Corvus caurinus) in the field. No quantitative
>study has been made of the geographic variation in these
>vocalizations. In this study, 26-34 crow roosting calls were
>recorded from each of four locations: Seattle, NE Olympic
>Peninsula, San Juan Island, and Nanaimo (Vancouver Island, British
>Columbia). Discriminant function analysis of five call
>characteristics was used to provide a quantitative method for
>categorizing calls. One hundred percent of calls from distinct C.
>brachyrhynchos (Seattle) and C. caurinus (Nanaimo) populations were
>correctly classified. Eighty one percent and sixty five percent of
>Olympic and San Juan Island calls, respectively, were classified as
>C. caurinus calls, indicating an area of geographic overlap. This
>overlap may be due to genetic hybridization in calls, environmental
>effects of early exposure to the calls of both species, or simply
>sympatric overlap in species ranges (mixed species flocks).

Jim, this sounds as if there is a bimodality in crow call types in this
area and nothing inbetween. Did I interpret your abstract correctly? If
so, this is evidence clearly in contradiction of what Gene and I wrote.
However, you mentioned "genetic hybridization in calls," which sounds as if
there might have been intermediates. Or did you just mean one crow giving
2 call types?

Very interesting stuff, and I would like to hear more about it.

Of course, according to tradition (i.e., Jewett et al., Birds of Washington
State), Seattle crows are supposed to be both _caurinus_ (at and near the
coast) and _brachyrhynchos_ (away from it). Where was your roost?

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416