Date: 7/10/20 7:42 pm
From: Torrey <tgagetomlinson...>
Subject: [obol] Black Storm-Petrel
All,

After returning home and doing research on Storm-Petrels, a family I
have limited experience with, I’ve come to the conclusion that the
dark rumped Storm-Petrel John Sullivan and I saw earlier today was a
Black Storm-Petrel. Below is my description on eBird of the bird, and
the link to the checklist.

https://ebird.org/checklist/S71324546

I initially saw this bird around 9:30 AM. It was very close to shore
(~50-100 yards offshore), among the second or third set of breakers
and flying northwest. I immediately realized that I was looking at a
Storm-Petrel, an extraordinary bird this close to shore in any case.
After the bird had flown maybe about 200 yards northeast and was just
beyond the breakers, John was able to get on it and we followed it as
it flew off t o the north about half a mile out before it disappeared.

One would normally expect Fork-tailed Storm-Petrel at this location,
but I quickly realized that it was much darker than Fork-tailed
Storm-Petrel, which I've seen a number of times. At this point I began
noting the fieldmarks of the bird instead of trying to identify a
specific species, as I have little Storm-Petrel experience beyond
Fork-tailed. I have seen Ashy, Black and Wilson's once on a pelagic
out of San Luis Obispo county, but I'm not familiar with any of these
species.

The most obvious fieldmark on this bird was the completely dark rump
and back. The carpal bar was not prominent as it would be on a Leach's
or Wilson's Storm-Petrel—not to mention the white rump that is
obvious on Wilson's and most Leach's Storm-Petrel. I didn't see it
close enough to discern any color difference that would determine
between Ashy and Black. Most notable was the lack of pale coloring
that stood out on the back and the dor sal side of the wings. This
bird had a methodical, consistent wingbeat that resulted in a smooth
and direct flight, unlike the shallow erratic flight of Ashy or
springy Nighthawk-like flight of Leach's. It dropped down in the water
for no more than several seconds about three times as it flew along.
At this point it had flown too far to observe it down in the water.
When it was approximately a quarter mile offshore, it briefly flew
among a flock of Red-necked Phalarope, which provided a good point of
reference. This Storm-Petrel had noticeably longer wings than the
Phalarope (which have a wingspan of 15 inches, ASSP wingspan of 18
inches, LESP 20 and BLSP 22).

These fieldmarks led us to the conclusion that this bird was most
likely a Black Storm-Petrel. However, both John and I were hesitant to
call it before we had done research beyond what we were capable of
doing on phones with spotty coverage. After reading several in depth
descriptions of Black, Ashy and Leach's Storm-Pe trels, and viewing
images and videos of all three in flight, I concluded that this bird
was indeed a Black Storm-Petrel.

*It should be noted that a large percentage of Leach's Storm-Petrel
that breed on Isla Coronado, Isla de San Benito and Isla Guadalupe off
the coast of Baja California exhibit predominantly dark rumps compared
to the light rumped population in the Northern Pacific and Atlantic
Oceans (Ainley, 1980). It would seem an even rarer occurrence to see a
dark rumped Leach's Storm-Petrel off the Oregon coast than it would a
Black Storm-Petrel. However, I imagine that the distribution of dark
rumped Leach's Storm-Petrels is likely not something that has been
extensively researched and is, needless to say, not a top priority in
the ornithological community. This being said, I eliminated this
species based off of the smooth flight pattern of BLSP and the obvious
carpal bar present in LESP that was lacking in this bird.

I will submit to ORBC. This is the 7th stat e record, should it be
accepted.

Best,

Torrey

Torrey Gage-Tomlinson

Biological Sciences

<tgagetom...>

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