Hello All,
For some time now we have noticed that many species of spring migrants are first observed way to the north of Southeastern Washington, such as swallows, flycatchers and some warbler species. We now have come up with a plausible reason for this happening. Enter the long thought on "Back-fill Theory". We believe that as migrants arrive they generally zero in on the best conditioned habitat and the largest consistent sources of food. Over time due to survival rates populations now head as far north as the air temps will allow. So the very best nesting sites are where there is great habitat and abundant insect numbers early on in the season. So the bulk of any population heads north and establishes the foreward territories in the prime habitats. As time progresses those individuals arriving later are forced to nest further to the south until they finally reach dry, hot Southeastern Washington. What do you think?
Later Mike

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Mike & MerryLynn Denny
323 Scenic View Drive
College Place, WA 99324
509.529.0080 (h)

IF YOU HAVEN'T BEEN BIRDING, YOU HAVEN'T LIVED!
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