HI:
I thought someone might be interested in this!

Ian "Birdbooker" Paulsen
Bainbridge Is., WA, USA
ipaulsen at linknet.kitsap.lib.wa.us
"Rallidae all the way"

---------- Forwarded message ----------
Date: Wed, 4 Apr 2001 19:35:39 -0600
From: Brett Walker <pancaminando at HOTMAIL.COM>
To: BIRDCHAT at LISTSERV.ARIZONA.EDU
Subject: [BIRDCHAT] Brewer's/Timberline differences

Dear Birdchatters,

Sorry for the delayed reply to Jim Rising and Jeff Price's recent emails
regarding the possible split of Brewer's (Spizella breweri breweri) and
"Timberline" (S. b. taverneri) sparrows.

A couple of points about differences between the two in Montana, where their
ranges overlap in latitude. One point to note is that, it's not just the
magnitude of the differences between them that are important, but whether
the differences in each character occur simultaneously when crossing from
the breeding range of one to the other.

Our results from Montana match those published by Klicka et al. 1999 in
terms of morphology, habitat use, and timing of breeding. Timberlines are
consistently larger (even between breweri and taverneri populations only 110
km apart), nest in sub-alpine krummholz shrubs, and nest about 4 weeks
later.

We're in the process of analyzing genetic data from a range of breweri and
taverneri locations in western Montana, so we don't have that info just yet.
Differences in song are often apparent in the field, with Timberlines
using a narrower range of frequencies, but there is so much variation among
individuals that it may swamp differences between the two groups. Klicka's
analysis of differences in song also may not be appropriate because of the
category of songs they used in the analysis. With luck, it'll be published
by this winter.

There are lots of different avenues that would help resolve this issue,
including testing for differences in physiological tolerances referred to by
Jeff Price, or for differences in parasite specificity, and molt strategies,
to name a few.

Regardless of whether they split it or not, the AOU committee definitely has
to be conservative. That raises the question of why they were lumped in the
first place (taverneri was originally described as a separate species in
1925)? Food for thought!

Good birding,
Brett Walker

pancaminando at hotmail.com
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