Subject: Keystone and Indicator
Date: Jan 13 21:53:31 2002
From: JLRosso at aol.com - JLRosso at aol.com


Thanks to the members of Tweeters for their responses to my question on
keystone and keynote. The group never fails. Yes, it seems that keynote is a
mistake, and keystone is used widely to denote species whose influence is
much greater than their numbers.
I realize that the term "indicator species" is used to express what I thought
"keynote" species expressed: a species whose population fluctuations
demonstrates the health of a particular habitat.
I came across an article that discussed the population of Rusty Blackbirds.
Its population has plummeted in the last 40 years. Here is a congener of the
Brewer's Blackbird. The Brewer's Blackbird's population has been increasing
over the past 40 years (and has become an indicator species of parking lots).
Rusty Blackbirds serve as an indicator species of boreal forests.
Obviously there is more to the success of a species than its food gathering
abilities brought about by the shape of its beak. If you compare the beaks of
the Brewer's and the Rusty Blackbirds they are quite similar, but one species
has made adjustments to change and one has not. I am intrigued by what it is
that keeps the Rusty Blackbird from the plasticity of the Brewer's Blackbird.
But then that is why it is an indicator species.
I also came across an interesting site explaining how the Red-naped Sapsucker
is a keystone species.

Jim Rosso
Sammamish
jlrosso at aol.com
www.birdcentral.net