Subject: Range expansion of Anna's Hummingbird
Date: Jan 8 20:23:19 2004
From: Mike Patterson - celata at pacifier.com


I keep forgetting that the majority of birders probably
don't remember a time when Anna's Hummingbird was rare
in Oregon and Washington (or when you could do a coastal
Christmas Count and miss starling). The first Anna's
Hummingbirds in Portland were found in 1965 and the first
in Seattle were in winter 64-65. Breeding was not confirmed
in Oregon until 1981 (though they were almost certainly doing
so prior to 1981).

It's unlikely that a BBS would have even had a chance to
pick up Anna's Hummingbirds on a BBS north of Douglas Co.,
Oregon were it nests open poison oak savannah and residential
areas before the mid-80's. The nesting sites here in Clatsop Co.
(which were identified in the late 90's) are in a residential
holly tree and an open salal covered hillside. Most BBS routes
just don't go through good Anna's Hummingbird breeding habitat.
My BBS route from northern Coast Range to the Columbia River
which I've been doing since 1990 averages 7.3 +/- 2.6(SD).
I still haven't recorded an Anna's.

There have been no Anna's recorded anywhere near the Rufous
lek at the Neawanna in Seaside and Rufous and Anna's do not
appear to share breeding habitat preferences generally. The
only place where competition is likely to occur is at hummingbird
feeders and the Anna's at my feeder make themselves scarce when
the very aggressive Rufous Hummingbirds show up in March.

Anyway, knowing that there just weren't enough Anna's Hummingbirds
in Oregon and Washington prior to say 1990 to explain any decline
in Rufous Hummingbirds through a significant chunk of the BBS trend
data and given that the two species do not have the same habitat
preferences during the breeding season (and that Anna's don't even
appear in most of the breeding range of Rufous Humingbird), it seems
unlikely that Anna's Hummingbird is in anyway responsible for any
decline in Rufous Hummingbird.

So, we're left with general habitat degradation.

References
Marshall, D.B., M.G.Hunter, and A.L.Contreras, Eds. 2003 Birds
of Oregon: a general reference. OSU Press.

Zimmerman, D.A. 1973. Range expansion of Anna's Hummingbird.
American Birds 27(5)827-835.

--
Mike Patterson
Astoria, OR
celata at pacifier.com

Half-a-bee, philosophically must ipso-facto half not-be.
But half the bee, has got to bee Vis-a-vis its entity...
d'you see?
But can a bee be said to be or not to be an entire bee
When half the bee is not a bee due to some ancient injury?
-Monty Python

http://www.pacifier.com/~mpatters/bird/bird.html