Subject: [Tweeters] Is the range of Annas hummingbirds artifically being
Date: Feb 22 13:42:17 2006
From: Dennis Paulson - dennispaulson at comcast.net


Rob Sandelin wrote:

So when I read about the levels of human intervention in keeping Anna's
hummingbirds here I wonder if this is such a good idea. What are the
ecological impacts of the actions of artificially supporting high
levels of
these birds? Do they compete with, perhaps drive out the native Rufus
hummingbirds? Assuming early flowering resources are limited, what
impact
does this unnatural residency of Annas have on migrating Rufus? Do they
pass disease or parasites to other birds? Are we propping up a
species that
perhaps does not belong here to the detriment of others? It seems
like its
one thing to provide nutrients to native birds throughout the winter,
maybe
its another thing to artifically support the winter range of a species.
----

Our feeding has probably enlarged the winter range of many, many
species; certainly the question about Anna's must be answered
strongly in the affirmative. I also question what we're doing to bird
populations by the massive subsidy we provide them year in and year
out. I feed birds because I like to see them in my yard (a Townsend's
Warbler is eating suet right outside my window as I write this), not
because I think they need it, and I assume most people see it that
way. Thus we can admit it's a selfish reason, so that should make it
more defensible to stop at any time! It's the same old story for Homo
sapiens in our effect on the world: a few people can do just about
anything to the environment, with no harm done, but when many, many
people do it, the effects may be severe.

I continually wonder about the effects of large-scale bird feeding,
and others have done so as well, but I've never seen a cautionary
"Pause" sign put up by anyone. Much has been written about the harms
of watching TV, but no one has pursued a very effective campaign
against it, in part because the great majority of people in our
society like to do it. The same is true of feeding birds, I think.

On the subject of hummingbirds, I have seen no change in the numbers
of Rufous Hummingbirds in my yard since Anna's colonized it a decade
ago. We have never had an adult male Rufous here, I presume because
they don't breed in such urban situations for the most part, but I've
been consistently surprised that they don't visit in migration. There
are small numbers of female and immature Rufous every summer, mostly
in migration. With all the people on tweeters who have been feeding
hummers for some time, there should be enough information now to know
if Anna's has affected Rufous.

It would be interesting to get figures from southeastern Arizona,
where hummingbirds have been fed en masse for many decades. The
number of feeders surely keeps going up, but the number of Anna's
Hummingbirds there has increased at an even higher rate. Right now
Anna's is the most common species at many feeders over much of the
year there. Are other hummers less common because of this? I don't know.

I believe I wrote earlier about the dearth of hummingbirds in
northwestern Mexico on two recent September visits. If there is any
effect from feeding hummingbirds, I wonder if it isn't keeping birds
in Arizona through the fall (I assume the number of feeders drops
precipitously just across the border) that would have otherwise
pollinated Mexican flowers. I hope some Mexican ornithologists or
botanists are keeping track of this.

Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382

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