Mike, Western Kingbirds nest very commonly in large deciduous trees in
Washington, particularly those around farmhouses, but I've never seen a
nest in a conifer. I still think they may have evolved in association with
riparian areas in the dry parts of the West, and it was easy for them to
"jump" to tree groves as people settled the area and planted trees. Black
locusts, cottonwoods, Siberian elms. They are still common in such
situations in this region, but then they made another "jump" to utility
poles, where perhaps the majority of them nest at this time. What a
fascinating story of the effect of humans on a bird species!

The whole story about the distribution of birds across the Great Plains
needs to be told. Huge areas of grasslands without a tree can now be
inhabited by Western Kingbirds and Swainson's Hawks, which will nest on
power poles, and the planting of trees at homesteads surely assisted in the
dispersal of many species from both east and west. Some of the
hybridization between related species, e.g. Bullock's and Baltimore
orioles, was probably facilitated by this.

I meant to mention after my trip to the Columbia Basin that Common Raven
nests were common on the big power towers near Dodson Road. Here's a
significant nest predator that's been aided and abetted in its occurrence
by humans.

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