On Sep 22, 2009, at 4:35 PM, rccarl at pacbell.net wrote:

> An excellent summary of this issue is in: Food for thought:
> supplementary feeding as a driver of ecological change in avian
> populations. Gillian N Robb1, Robbie A McDonald2, Dan E Chamberlain3,
>
> You can get a free copy of this by googling it. I have the pdf if
> you have trouble.

A blog entry on this issue where he talks about Gillian Robb and Dan
Chamberlain's work previously mentioned and another related paper that
shows the benefits of feeding. Even if you don't like to read
scintific papers read these --- they're not difficult to understand
and you will find something to think about.

http://scienceblogs.com/gregladen/2008/04/should_you_feed_the_birds.php

The papers and links to PDFs are:

Robb, G.N., McDonald, R.A., Chamberlain, D.E., Bearhop, S. (2007).
Food for thought: supplementary feeding as a driver of ecological
change in avian populations.
Frontiers in Ecology and the Environment, preprint(2008)

http://www.frontiersinecology.org/current_issue/bearhop.pdf

Robb, G.N., McDonald, R.A., Chamberlain, D.E., Reynolds, S.J.,
Harrison, T.J., Bearhop, S. (2008).
Winter feeding of birds increases productivity in the subsequent
breeding season.
Biology Letters, 4(2), 220-223.

http://rom.exeter.ac.uk/documents/Bios/sb312/Robb%20et%20al.%202008%20Biology%20Letters.pdf
http://rsbl.royalsocietypublishing.org/content/4/2/220

Supplementary data (and the published PDF) are at the Royal Society
site.

Dan Chamberlain has done a bunch of interesting work related to this
field. See his CV for titles of significant papers.

http://www.bto.org/aboutBTO/cvs/dan_chamberlain.htm

Plus a couple of other commentaries

http://www.bioedonline.org/news/news.cfm?art=3791
http://www.physorg.com/news126438925.html

It really does seem (as Rob pointed out) that there are more questions
than answers. Perhaps some well-organized citizen science needs is
there to be done? Plus there is the question about "is it good idea"
even if it's clear that feeding improves productivity. For some
species I would think yes. For others, like American Crow, clearly not.

I'm not sure how you can resolve this issue with just banding data: it
might show correlation in movement with feeding opporunities but not
causation. But the Bearhop/Robb tries to control the site and measure
the birds directly.

There is also winter range change in the Anna's Hummingbird over the
past 45 years with birds overwintering in the urban PNW which seems to
be related to feeding (both directly through feeders and indirectly
through exotic plants). Seeing an Anna's Hummingbird at 28F with snow
falling on Capitol Hill defending it's feeder during last winters cold
snap convinced me that food availability and not "global warming" is
the more likely cause. But I don't know of any formal work on this
(please send me references if you know of them).

e.g. http://depts.washington.edu/natmap/maps/wa/birds/WA_annas_hummingbird.html

One wonders (given the other recent topic of discussion) if this is
true of Western Scrub Jay northwards range extension too? Do they like
the extra food opportunities around here once they get here? Perhaps
the songbirds that you are feeding at your feeders are then feeding
them (and the Cooper's Hawks and the ...). Is that good?
--
Kevin Purcell
kevinpurcell at pobox.com
twitter: at kevinpurcell



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