Actually, a better question to ask is - has the wintering status and or
earliest migration dates changed for any other Empidonax species, or related
Tyrannids?
When Oregon got its first winter Violet-green Swallows we did consider the
precedent of Barn and Tree swallows relevant.
Wayne
From: "whoffman" <whoffman@xxxxxxxx>
To: "Tom Crabtree" <tc@xxxxxxxxxx>
Cc: "obol" <obol@xxxxxxxxxxxxx>
Sent: Monday, April 6, 2020 4:55:24 PM
Subject: [obol] Re: Fwd: Re: Birds and Climate Change
Hi -
I got it Tom, This is really, really unprecedented.
But when I left Oregon in 1977 and moved to Florida, I did not expect Oregon to
EVER get a swallow on a CBC. Currently which species of North American swallows
have not been well-documented in Oregon and/or Washington between Dec. 15 and
Feb 1? Cave Swallow and what else? maybe Purple Martin?
The only explanation that makes sense for me for the change in seasonal swallow
distribution is that some environmental signal that triggers migration
(obviously not just day length) is no longer available to them or reliable for
them, and a significant minority of individuals misread whatever signal this is
and head back north way way early.
At first when it was pretty much just Barns Swallows, there was a lot of
speculation that these were migrants from the recently established Argentinian
breeding population, but this explanation does not work for Tree Swallows,
Violet-green Swallows, Cliff Swallows, etc.
My real point is that we have accepted the winter swallow phenomenon too
easily, without a good explanation, and are too willing to assume that similar
things will not happen with other bird groups.
Wayne
From: "Tom Crabtree" <tc@xxxxxxxxxx>
To: "obol" <obol@xxxxxxxxxxxxx>
Sent: Monday, April 6, 2020 3:57:17 PM
Subject: [obol] Fwd: Re: Birds and Climate Change
Granted, climate change is changing arrival dates, but not by two months in
the past couple of years. Speaking of which, here are all the records of
Willow Flycatcher in North America this year showing their current arrival
dates and pattern:
I'm not seeing a lot of early arrivals in our neck of the woods. It hardly
seems like a slam dunk for Oregon (or California, or Arizona or even Sonora
for that matter). Casually accepting exceptional records with out
exceptional documentation would do future researchers a severe disservice.
Tom Crabtree, Bend
