Subject: Re: Hummingbird feeders & migration
Date: Jul 29 10:48:04 1996
From: Dennis Paulson - dpaulson at mirrors.ups.edu


Great account in response to Steve Preston's query, Michael!

I have only one thing to add, in response to your comment about Anna's
Hummingbird.

"This species is pretty non-migratory, but wide-wandering. It winters where
it finds itself when the days start to get short (and maybe it's daylight
duration that triggers it to sit tight--can anyone comment on this?)."

I would say "pretty non-migratory" is an understatement. I think the
species is basically resident, but that there is a dispersal of juveniles
away from the Pacific Coast/Southwest breeding range during the fall.
Anna's were originally restricted to CA and southwest OR, as I understand
it, and in relatively recent historic times have extended their range both
north to southern BC and east to southern AZ. I think this was made
possible entirely by the proliferation of hummingbird feeders, and, if you
suddenly made hummingbird feeding illegal, there would be a huge mortality
in this species, probably most of the individuals present outside the
original range. I don't think day length triggers a response to *not*
migrate; they are just genetically programmed to be resident.

We have made substantial changes in bird distribution and migratory
behavior (all those Baltimore Orioles that spend the winter in the NE now)
through the use of feeders, and I'll admit I've wondered what kinds of
change have been worked on hummingbird biology and genetics by the massive
feeding program. For example, in many communities in eastern WA, I suspect
there are now more hummingbirds in the towns than out in the woods, as
feeders represent such an easy and dependable source of nutrition. When
people go on field trips over there, they often stop at a roadside
attraction with hummingbird feeders to get their hummer fix. Are hummers
being drawn out of natural environments, where they were primary
pollinators of some plants? Probably not anything to be too concerned
with, but an interesting idea to contemplate.

By the way, for those birders who'd like to initiate or further their
encounters with Black-chinned Hummingbirds in Washington, they are regular
in small numbers at feeders in the Winthrop area, where they coexist with
large numbers of Rufous and Calliope.

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