I think many of us (including myself) often fall into a trap in estimating
the impacts of aiding one or more species, or the impacts of a new species
entering an ecosystem. When Anna's hummers become common in a new area due
to feeding or a combination of feeding and global warming (feeding the oil
companies) we may be too quick to think about the impact on the closest
related species in the area - in this case the Rufous hummer. It may be
more instructive to look at the niche the Anna's occupies and the difference
between its niche and the Rufous, then ask what the Anna's might impact in
that niche. The most obvious difference between the niche of the Anna's and
the Rufous is that the Anna's is here in the winter. It may well be that
the impact on the population of some little midge or fly species that flies
in the winter and that it eats is more critical.

On a similar note, when we feed birds in general the increased Eastern Gray
Squirrel survivorship through the winter from them getting that "bird food"
may have more impact than the feeding of the birds themselves. I don't know
which species of birds' eggs and chicks the Eastern Gray Squirrel usually
gets when they feed on them, but harm to these prey species may be more
critical to our bird diversity and populations than the more direct affects
of feeding the bird species that get that bird food. If Starlings and House
Sparrows get much of that food, the impact of these species on other
organisms may be the bigger issue.

While I don't normally feed birds, I suspect the benefits of bird feeding
winning over new advocates for wild birds among the human population may be
greater than the harm to the species that will be the losers in the bird
feeding equation.

Stewart Wechsler
Ecological Consulting
Invasive Removal, Native Restoration
West Seattle
206 932-7225
ecostewart at quidnunc.net

-Skilled efficient manual removal of Himalayan Blackberry
-Advice on the most site-appropriate native plants
and how to enhance habitat for the maximum diversity
of plants and animals
-Habitat Restoration
-Educational programs, nature walks and field trips
-Botanical Surveys

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.375 / Virus Database: 268.0.0/267 - Release Date: 2/22/2006