[obol] Spring bird phenologies

From: Joel Geier <joel.geier@xxxxxxxx>
To: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
Date: Sat, 26 Apr 2014 20:06:07 -0700
Hi all,

I've had various folks try to bend my ear ever since I tried to relay on
"just the facts" as to early Swainson's Thrush reports in the region
that I pay attention to.

To be as frank as possible: 

(1) I am just as skeptical as anyone else on this list who has expressed
doubts about some of these early reports.

However:

(2) I think that some of my fellow skeptics are getting bent way too far
out of shape in regard to what these early reports really represent, and
the urgency of grinding them down with their boot heels until the
observers repent of their wicked ways.

Because:

(3) First-of-season reports are NOT robust statistical indicators of the
timing of bird migration. They are a function both of observer density
and random chance. If anyone thinks that "first of season" reports are
useful as a measure of bird migration, I suggest visiting this page:

http://en.wikipedia.org/wiki/Normal_distribution

and staring at it hard for as many hours as it takes, until you see an
Eskimo Curlew staring back at you. And then wait a few minutes longer,
until the Eskimo Curlew appears to be cross-eyed.

Because:

(4) This is what a diffusion front looks like. See:

http://en.wikipedia.org/wiki/Fick%27s_laws_of_diffusion

which is about molecules but it could just as well apply to migrant
birds and the random perturbations that they face. The reason why it's
called a "normal" distribution is because it's the normal result of
adding up a lot of random effects.

Take a look at the tails of this distribution, and think what happens
when you multiply your observer density by a factor of 10. Yep, you're
going to start sampling much farther out on the tails of the
distribution.

So if the number of keen birders in Oregon goes from the 20 or so
old-timers from the 1970s that we always hear about, to the 1000+
birders on OBOL (not to mention the 500+ subscribers on other regional
lists), why should anyone be surprised that the first arrival reports
tend to creep up with time?

Sure, some of the early reports might be erroneous (I suspect that many
or most of them are) but DOES IT REALLY MATTER THAT MUCH?

I mean, I MEAN ...

Here we are in 2014. Ukraine and Russia are close to war. Syria has
something like 6 million displaced refugees. War is still raging in the
Congo and Ebola is breaking out in Guinea. A racist, nut-case rancher in
southern Nevada has called out militia groups dressed in fatigues and
carrying assault rifles, pointing them at BLM employees to "defend" him
against the federal gubbermint just because they're trying to collect
$1.50/head per annum grazing fees for his cattle that have been sucking
up all the grass on OUR public land.

Desert Tortoises, Greater Sage-Grouse, Yellow-billed Cuckoo, Streaked
Horned Lark, Oregon Vesper Sparrow and other birds are all still in deep
trouble, the planet is undeniably overheating, mangroves are
disappearing along with coral reefs and the whole nation of Kiribati.

And here we're bickering over whether a week-too-early report of
Swainson's Thrush should be accepted as valid? 

Come on, folks, this is just ridiculous, both from a mathematical and
social perspective!

But ... just to provide some forum-appropriate content, here are a few
expected (and record early dates, following the species name) for the
Corvallis area, based on Alan McGie's compilation which in turn is based
on 35+ years of data from the Corvallis area.

Good birding,
Joel


Apr 17,Cassin's Vireo,34,Mar 26
May 02,Western Wood-Pewee,24,Apr 07
May 03,Swainson's Thrush,27,Apr 05
May 04,Black-headed Grosbeak,33,Apr 23






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[obol] Spring bird phenologies

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