[obol] Re: id help needed! (bud break in the Willamette Valley)
- From: Wayne Hoffman <whoffman@xxxxxxxx>
- To: joel.geier@xxxxxxxx
- Date: Thu, 23 Oct 2014 20:15:03 -0700
Hi, Joel -
You posed an interesting and important question,
"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."
I do not see this a a major problem for spring arrivals. I suspect that
spring insect availability increases continuously from bud break on through
the breeding season. So food availability may be higher now than in the
past.
There may instead be a problem for birders: it is so much more satisfying
to watch warblers in a Big-leaf Maple at bud break than when the tree is
leafed out!
Possibly there could be a pinch at the other end, when leaves are turning
and dropping earlier, relative to the migrants' programmed departure times.
Wayne
On Thu, Oct 23, 2014 at 7:13 PM, Joel Geier <joel.geier@xxxxxxxx> wrote:
> 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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