[va-bird] Sibley Hummingbird Comments

Since I was the culprit who first posted the article from Massachusetts about 
wintering hummingbirds one would think I might have learned, but I tread here 
once again with great care.  I have permission from David Sibley to post a 
comment he sent to the Massachusetts network on the hummingbird debate: 


I think this is an interesting and very worthwhile discussion, and while
attempting not to get too involved in the debate over the general pros and
cons of bird feeding, I wanted to support the comments of Mark Szantyr and
Brian Krisler. I think the general rule is that birds migrate when their
bodies tell them to migrate, and in the direction that their brains compel
them. Many of us provide lots of high-quality food all winter, but it never
induces Tree Sparrows to stay later than April. Virtually all of the
Ruby-throated hummingbirds migrate south while feeders are still filled. The
only exceptions are birds that are injured, possibly "not right in the head"
or in some other way hindered in their migration.

The Rufous Hummingbirds that show up in Massachusetts are definitely off
course, just by their arrival here we can say that they are somehow hindered
in their migration. They arrive here because their brains haven't directed
them the "right" way and it's most likely that the ones that stay think they
have reached their wintering grounds. As Mark Szantyr suggested, there is an
adaptive reason for this, and we can see it in things like the expansion of
Cattle Egrets across the globe or the expansion of the winter range of
Rufous Hummingbirds across the southeast. These "lost" individuals
occasionally find suitable habitat, and if they survive long enough to
reproduce they can give rise to a change in the distribution of the species.
They are the pioneers for their species. Climate and habitats have always
been ephemeral. The birds that show up outside their normal range are not
necessarily "lost" or in the "wrong" place. This is the birds' way of
prospecting new areas and trying to keep up with a changing world.

I think Mark Lynch got to the heart of it when he said this is a human
problem. I am sure it must be very difficult to watch a hummingbird succumb
to the cold, and I'm glad I don't have to deal with it as Mark does, but I
think that in most (nearly all?) cases the hummingbirds involved will not be
helped by taking down the feeders. There is no reason to think that after
spending the month of October at a feeder in Massachusetts, a Rufous
Hummingbird will be able to reorient and move south to a more suitable
climate. More likely it will drift around New England searching for food, or
if it moves directionally it may simply continue to the east (the direction
that got it here in the first place). The sad fact is that most of these
birds (at least in Massachusetts in our current climate) are doomed. Taking
the feeders down is like simply pulling a curtain and hiding them from our
view.

Now I'm not suggesting that this will help Mark to deal with the people who
find themselves hosting a hummingbird in December, or that leaving the
feeders up is the right thing, but I don't think it's accurate or fair to
suggest that taking the feeders down is good for these individual birds. I
also think that more drastic intervention is wrong. Heck, for all we know
some of the current crop of Massachusetts Rufous Hummingbirds could be the
offspring of "Ruffy" - the consequences of human meddling. But the expansion
of Rufous Hummingbird's winter range across the southeast in recent years
and now spilling over into New England has been aided by feeders and flower
gardens and other human habitat modifications. In the 21st century it is
impossible to separate human influence from almost any bird distribution in
North America.

David Sibley

Harry Glasgow

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