Dave’s caution is quite justified. Storm-petrels are quite variable and even
from a stable platform not easy to observe in detail.
In 1975 we ended up with a lot of dead Leach’s around Eugene and these made a
brief appearance en masse at a SWOC meeting before being sent off to a museum
in California ( I trust the statute of limitations has passed on this
indiscreet contravention of the wildlife laws). There was variation in rump
color and as I recall we had a couple that had mostly dark rumps.
The museum’s report on the identity of those birds was in an early SWOC Talk
and could probably be unearthed.
Alan Contreras
Eugene, Oregon
acontrer56@xxxxxxxxx
On Oct 19, 2016, at 10:42 AM, David Irons <LLSDIRONS@xxxxxxx> wrote:
Greeings all,
After spending nearly two hours yesterday with Fork-tailed Storm-Petrels
almost constantly in my scope, I echo Jay Withgott's cautionary commentary
about the variability in appearance of this species. In my zeal to see my
first Ashy Storm-Petrel in Oregon, I latched on to a couple worn and
considerably darker Fork-taileds and had to watch them for several seconds
before positively identifying them as such. I remarked aloud a couple times
to others gathered at Boiler Bay yesterday that I was surprised by how
variable the Fork-taileds were. Most of the Fork-taileds that I seen have
been from boats, where lengthy scope studies of individual birds don't
happen. This was by far my best experience with this species in terms of
studying individual difference. On many birds the wings looked almost
uniformly dark above, with very little contrast between the dark coverts and
lead edge of the wing and the rest of the wing. Also, many the amount of
contrast between the dark underwing linings and the much paler undersides of
the flight feathers was greatly reduced. On many individuals the head and
underparts looked considerably darker and it was near impossible to make out
the dark patch around the eye.
Once we saw an actual Ashy Storm-Petrel it was noticeably darker than even
the darkest Fork-taileds and its flight style and proportions were quite
different. It looked straighter-winged, longer-tailed, slightly smaller, and
slighter bodied in direct comparison. The flight was characterized by what I
would describe as a stiff-winged flutter that was unlike the more languid
wingbeats of the Fork-taileds.
It was fun, although exhausting to make the nearly four-hour round trip for
just two hours of birding (had to go to work). I could have spent all day at
Boiler Bay yesterday just watching storm-petrels. I do wonder about the
reported counts. As Phil Pickering posted yesterday this seems to be a
localized event and the birds that I was watching weren't flying by or on the
move. I watched many birds making small loops as they fed through the same
areas flying into the southwesterly winds. I wonder if some birds were being
double and triple counted as they made repeated passes by our various viewing
stations. I saw just two Ashy Storm-Petrels yesterday and I felt those could
be individually identified by varying amount of light coloration in the
upperwing coverts.
Dave Irons
