[obol] Re: Spring Arrival Dates: Long and likely annoying for some
- From: David Irons <llsdirons@xxxxxxx>
- To: Brandon Green <brandon.green18@xxxxxxxxx>, OBOL Oregon Birders Online <obol@xxxxxxxxxxxxx>
- Date: Fri, 25 Apr 2014 07:33:50 +0000
Brandon,
For more than a week now (since at least the 16th of April) there have been
almost daily reports of Swainson's Thrushes showing up on OBOL and in the daily
eBird rare bird alert for Oregon. I believe that every single one of these
reports is suspect. I looked at the eBird map that you provided for all-time
April reports of Swainson's Thrushes. It covers many years and has several
clusters of reports that are highly questionable. That said, there are some
from observers who none of us have any reason to doubt. These reports, seem
to be clustered (for the most part) over the last few days of April
(27th-30th). I consider any report in April to be early and any report before
about the 25th of April to be exceptionally so. We can argue over how to define
"exceptional," but that's really not the point.
We go through this exercise every Spring on OBOL. The fact of the matter is
this, not that many birders pay close attention to spring arrival dates and if
asked many could not tell you when Swainson's Thrushes, Yellow Warblers,
Warbling Vireos, or Willow Flycatchers normally arrive in the Willamette
Valley. Without an understanding of spring migration phenology, one is unlikely
to apply much rigor or objectivity to what they think they are seeing because
they have no reason to. If you believe what you are seeing is normal, why would
you question it? If on the 20th of April you see a bird that looks like a
Swainson's Thrush (the default w. OR thrush in the minds of many Oregon
birders) and you don't think or know that a 20 April Swainson's Thrush is
unusual, would you be skeptical about your own observation?
If you look around the OBOL 'room,' the folks who view these early Swainson's
Thrush reports with skepticism are folks like Jeff Gilligan–Jeff has been
birding in Oregon for 50+ years; Tim Rodenkirk–Tim goes birding almost every
day, keeps a very detailed database on the comings and goings of birds in Coos
and Curry counties. Tim can authoritatively answer almost any question about
the abundance, distribution, and seasonality of birds in these counties, I know
because I regularly ask him such questions; Wayne Hoffman–Wayne has been
birding in Oregon for decades and has been a very active birder since at least
the 1970's); Mike Patterson–Mike has been birding in Oregon since the early
1970's (at least). He has been the Oregon CBC editor for North American Birds
for about two decades and he has been banding along the Oregon coast
(Swainson's Thrush central) for 11 years. These are birders who have been to
this rodeo. We've all encountered out of season reports of Swainson's Thrushes
made by folks who were absolutely certain of what they saw. Swainson's Thrush
gets reported on an Oregon CBC every year. Hermit Thrush is the only Catharus
thrush that regularly winters in Oregon, whereas Swainson's is a mega-rare bird
here in winter. Swainson's also get reported somewhat regularly in late March
and the first 2-3 weeks of April, when Hermit Thrushes are the default thrush
in western Oregon.
Ever since I started birding seriously, I have paid particularly close
attention to migration/arrival/departure dates. Back in the mid-1980's David
Fix, Steve Heinl, and I shared an apartment at the base of Skinner's Butte in
Eugene (3rd and Pearl). During spring migration, we birded the Butte every
single day, often making more than one trip up the hill per day. At the
beginning of every season, we would make our predictions for the exact day each
neotropical species would first appear on the Butte. We were rarely off by more
than a couple of days. As the years passed and our sphere of "young guard"
birding buddies grew to include Matt Hunter, Dennis Rogers, Rob Fergus, David
Bailey and Jim Johnson, this game only intensified. We all started each spring
migration on a mission to find as many "first of the season" birds as we could.
If there were mid-April Swainson's Thrushes to be found, I dare say one of us
would have found them. I'm pretty certain that I've never seen a Swainson's
Thrush earlier than 3 May (and I was surprised by that one). Since those early
days, I've done a couple of stints writing field notes for Oregon Birds and
I've been Oregon's Regional Editor for North American Birds since 2003. In
order to write these columns, one has to be intimately familiar with migration
phenologies.
There are two additional phenomena that are somewhat universal in the birding
world. One might be described as "me tooism." The other is the tendency to
embrace oversimplified one-size-fits-all explanations when it comes to
explaining early or late reports.
Me Tooism -- Once a bird is reported by a seemingly trustworthy observer, it is
as though a permission slip has been issued to the rest of the birding
community. If an early report of say a Swainson's Thrush or Willow Flycatcher
is posted on OBOL, you can almost predict a number of "me too" reports in
subsequent days. "If birder X is reporting one, they must be around."
Oversimplified Explanations -- This season's example is the combination of
drought in California and the stretch of unseasonal warm and sunny weather that
we enjoyed during the first two weeks of April. At some point there was some
chatter on OBOL about birds arriving early in California and that the drought
and nice early April could explain some surprisingly early reports in Oregon.
Again, another permission slip was issued. A smattering of early arrivals occur
every spring migration. What we've seen this year can hardly be considered an
anomaly. Also, the generally poor understanding of phenology among rank and
file birders leads to birds being reported as "early" or "late" even when they
aren't. There were questions about the first Hammond's and Dusky Flycatchers on
Skinner Butte. These two species show up every year by the 15th of April, often
a few days earlier. This spring there have been a few species that have shown
up 2-5 days earlier than the normal FOS reports. However, aside from the flurry
of Swainson's Thrush reports and the likely incorrect report of a Willow
Flycatcher from Detroit Lake, I can't think of any reports that I found to be
shockingly early.
The California drought and warm spell probably shouldn't be offered as a the
reason for multiple Swainson's Thrushes being reported between the 15th and
20th of April (at least two and more like three weeks early). If you look into
the points of origination, the migration routes, and the timing of spring
migration for the many neotropical species that pass through Oregon in the
Spring, you'll realize that a single factor like the California drought, or the
period of nice weather we had in April is unlikely to have had a wholesale
effect on the entire suite of neotropical migrants. Some birds start in the
desert southwest, some start in Mexico and Central America, and others come
from as far away as South America. The routes taken to reach Oregon do not
follow a single pipeline running straight up through California.
Approximately three full months pass from the date when the first Rufous
Hummingbird (the earliest neotropical migrant) reaches the southern Oregon
Coast, to the date when the first Common Nighthawk (the latest neotropical
migrant) arrives in the Siskiyou Mtns. and the southern reaches of Oregon's
Coast Range. When they left their wintering grounds, these birds could not
have known that they would encounter drought conditions in central California,
or that a 10-14 day stretch of really nice weather would occur in Oregon during
early April. In reality, these comparatively local climate/weather anomalies
probably didn't alter the path or the timing of the migrations for most
species. Perhaps the early wave of Western Kingbirds that we had might be
attributed to birds finding no food in California's drought-stricken Central
Valley and continuing to push north, but it's hard to know. Most of the other
species that typically show up in the first half of April (Hammond's
Flycatcher, Pacific-slope Flycatcher, Cassin's Vireo, Nashville Warbler and
Black-throated Gray Warbler) appeared on schedule. In recent days, there have
been ever so slightly early Black-headed Grosbeaks and a Yellow Warbler, but
true outliers have been no more numerous than a 'normal' spring based on the
reports that I've seen.
I'm sure that I appear more skeptical than most about out of season reports.
This skepticism doesn't come from being a cranky, distrustful old guy who has
nothing better to do with his time than cast doubt on the reports of other
birders. My skepticism comes from 40+ years of seeing the same ID mistakes
repeated year after year. I endorse the use of eBird and I think it is a
wonderful tool. I have a similar opinion of OBOL, as it among the most lively
and educational statewide birding forums in North America. Despite these
endorsements, I do not accept (at face value) everything that I see reported
through via these forums.
If you think you are seeing a Swainson's Thrush in Oregon during April, I
encourage you to take and post photos. It may seem silly to document a species
that will be dirt common throughout much of Oregon a month from now, but if we
are to stretch the bounds of current knowledge, rigor, objectivity, and proof
need to be part of the process.
Dave Irons
Portland, OR
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