[obol] Re: id help needed! (bud break in the Willamette Valley)
- From: Joel Geier <joel.geier@xxxxxxxx>
- To: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
- Date: Thu, 23 Oct 2014 19:13:35 -0700
Hi all,
I agree with Dave Irons' detailed analysis that this looks like a
Wilson's Warbler.
I believe that the comment, about the two plates of undertail patterns
in Dunn & Garrett's warbler guide being "the most useful plates in any
field guide," is due to Mike Patterson, in a review of this field guide
that he posted on OBOL when it first came out.
About using vegetation as a clue to warbler ID, a cautionary note
(although it doesn't contradict Dave's analysis -- in fact it reinforces
it for this instance) is that the timing of spring bud-break in the
Willamette Valley has advanced by about a week, over the past decade.
This information comes in part from systematic observations made as part
of a global phenology project, by students and faculty of the Jane
Goodall Environmental Middle School (JGEMS) in Salem, which I've been
privileged to be a part of. The interesting thing (though this is
wandering off-topic) is that the fall phenology for trees changing color
and dropping their leaves has also advanced by about a week.
That might seem counterintuitive, as climate change has been extending
the frost-free season (astonishingly apparent this year -- it looks like
we could make it all the way into November before we have our first
frost on the valley floor). The simplified version of the explanation
that I've heard is that autumn leaf changes are basically dictated by
time-dependent chemical processes that are set in motion when the trees
leaf out in spring. So the season in which leaves are on the trees has
basically just shifted forward by one week, rather than becoming longer.
Getting back on topic, what I've noticed over my 18 years of residence
here in the Camp Adair area of the mid-Willamette Valley is that migrant
warbler species that used to peak in passage during big-leaf maples
bud-break, now tend to show up a bit later, during bud-break for Oregon
white oaks.
This makes sense based on the idea that neotropical migrants are
programmed to respond to changes in day length rather than temperature,
while trees are chemistry-driven critters that seem to respond more
directly to temperature, which influences the rate of chemical
reactions.
Obviously this creates a problem, if the calendars for migrant
wood-warblers and the trees that they depend on for insects continue to
diverge.The question is whether birds will be able to adapt fast enough,
through natural selection in favor of early migrants, to the rapid
changes that we're seeing in tree phenology.
Good birding,
Joel
Dave Irons wrote:
1. Vegetation -- The deciduous tree in the photo is just
starting to bud and leaf out. In the Willamette Valley that
typically happens from late March to mid-April with bigger
trees. You say this photo was taken in April, but don't give us
the exact date. I think that if this image had been taken in the
latter days of April the leaf out would be further along.
--
Joel Geier
Camp Adair area north of Corvallis
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