Hi -
I have 2 contradictory things to add to this thread.
First, we seem to be finally coming to a better understanding of gull migration
and winter distributions along and off the Pacific Coast. I'll get back to
this below.
Second, the past 3 years, and apparently continuing this winter, ocean
conditions off the coast have been very different than ever seen in the various
scientific databases available. Water has been very warm, nutrient regimes
have been unusual, toxic algae blooms have been more extensive, and through
more if the year than ever recorded in the past. So the accumulated
information on gull distribution might not apply to this winter as well as we
want. I thnk the current re-closure of the crab fishery because of Domoic Acid
levels is unprecedented.
Back to our better understanding:
In winter the most obvious birds, and often the most abundant birds offshore
are gulls. Between 5 miles and 30 miles offshore the dominant species are
Glaucous-winged Gull, Herring Gull, Thayer's Gull, sometimes California Gull,
and Black-legged Kittiwake. Western Gulls and Mew Gulls tend to stick closer
to the coast. The center of California Gull winter distribution is south of us
off California, but some winters quite a few remain off our coast. Thayer's
Gulls and likely Herring Gulls are much more abundant off Oregon and Washington
than off California. Glaucous Gulls are nowhere common in the northwest, but it
is likely that a lot more winter offshore than onshore.
Many Glaucous-winged Gulls, and some individuals of the other species winter
onshore, and are regulars at the various "Gull Wads" up and down the beaches,
but numbers increase greatly in stormy conditions. All of these species are
habitat generalists, and some show up inland as well each winter.
The details of winter distribution are very dynamic, and likely the offshore
winterers move hundreds of miles up and down the coast, and inshore and out
through the course of a winter, in response to weather conditions and food
availability.
When we see "rare" gulls on the coast in winter, broadly defined, many are
likely wintering offshore and just coming to land briefly. I suspect this is
the case with the 2 (my and Phil Pickering's) Kumlien's (Iceland) Gulls, and
perhaps also with the Slatybacked and 2 Lesser-black-backed Gull sightings as
well. Black-tailed Gull, a species recorded in most US states, but not yet in
Oregon, is likely also to be occurring offshore more often than on land in
Oregon.
Wayne
On 2/7/2017 12:09:35 PM, Phil Pickering <philliplc@xxxxxxxxxxx> wrote:
Cals presumably remain quite pelagic in winter, but most
indications are they are in fact greatly outnumbered in mid-late
winter by Herring/Thayer's offshore at this latitude, and that
during most years the majority must be wintering further south.
This is supported by pelagic data, a few older deepwater
surveys, and of course makeup of storm-driven flocks coming
off the ocean.
Assuming they were most/all adults I'd question if a pure flock
of hundreds of Cals in Feb here might not be very early staged
migrants. The spring migration of adult Cals along the coast
rarely comes close to matching what is seen in fall, so the details
of timing and route are a bit of a mystery.
Phil
-----Original Message-----
From: Tim Rodenkirk
Sent: Tuesday, February 07, 2017 10:44 AM
To: larspernorgren@xxxxxxxxx
Cc: OBOL Online
Subject: [obol] Re: re South Coast update
Just reading the "Pelagic Birds from Cruise Ships Along the Pacific Coast"
article in latest North American Birds
magazine, a fascinating article by Paul Lehman (I am currently stuck at home
with the crud). Interestingly under CA Gull
it says: "This is the dominant Larus gull offshore near the shelf edge,
including in winter, October-March."
I guess that answers my question.
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