Even more impressive than the Ruby-crowned Kinglet wave I reported last
week was an extremely rapid movement in Seattle on 16 April. In late
afternoon (around 6 p.m., long before dark) Tom Schooley and I had been
sitting in my back yard for some time keeping our eyes peeled for just such
a thing, when we saw a Yellow-rumped Warbler fly into a tall maple in the
ravine behind my house. In about 3 minutes, perhaps 10 of this species flew
through the same area, rapidly from west to east (or southwest to
northeast), and disappeared. They foraged in a single tree only for
seconds, then flew on. These would seem to be cases of diurnal migration in
small passerines, something I hadn't really realized occurred (except in
swallows and other flocking birds that we know migrate during the day).
Perhaps Yellow-rumped Warblers are in the same category as
pipits--migrating in cohesive flocks--but surely Ruby-crowned Kinglets
belong in a different category. And the warblers moved in a direction
exactly opposite that of the kinglets a few days before.
The next morning we watched another 10 Yellow-rumps feeding, also
in tall bigleaf maples, this time on Fidalgo Island, and the birds stayed
in the same trees for 20 minutes or more. Do passerines move through
fragmented habitats in city landscapes faster than they do through the more
extensive and continuous habitats in the countryside?
Watch for this phenomenon, birders.

Dennis Paulson
University of Puget Sound
dpaulson at ups.edu