Hi tweets, as the shorebird migration gears up for full swing, the waterfowl
tapers off and loons in particular seem to have, for the most part, moved
out of the local area. What I saw last weekend was an intriguing looking
loon. It was a long ways off, typical of Pacific and Red-throated Loons,
the Common Loon often much closer to shore... but it had white sides! Taken
by itself, this field mark is rather useless but is very visible from a long
distance and would likely be the first field mark that would steer an
observer into speculation. Is it a Pacific or is it an Arctic Loon? For
starters, I had to watch the bird for a few moments to be certain that the
white was not simply due to the way the bird was sitting on the water (they
sometimes preen with their bellies exposed-showing what appear to be white
sides). Interestingly, the white sides were visible at all times during a 5
minute observation. I was not pleased that the bird was a great distance
away but nevertheless, I was determined that I would not let a potential
Arctic Loon escape. As I watched the bird, I attempted to sort out other
features that would coincide with either Pacific or Arctic field marks. As
far as size goes, it appeared much smaller than the Common Loons that were
nearby, perhaps too small for what I would expect for Arctic. It was in
basic plumage, a few white spots were appearing on the otherwise dark
mantle. I thought it's profile was smooth and sleek like a Pacific Loon, it
should be more block-headed for Arctic, approaching the head-shape of Common
Loon. The white sides appeared to darken toward the rear flanks and I
thought this area should still be rather white for an Artic Loon. No
chinstrap was visible but the bird was much too far away to see this.
The bill was held horizontally as one would expect for Pacific Loon.

I have seen Pacific Loons show white sides before, but never to this extent,
so I was puzzled for a while. I was also hopeful that I might 'turn it into
an Arctic' but too many clues led toward a Pacific Identification. In fact,
as far as I could tell, it only had one arctic loon feature. This
experience reminded me how easily one can put too much weight on one or two
fieldmarks and mistake an identification whereas gathering as much evidence
as possible is a much more reliable method.

A few questions that I have are:

1) What would be the most likely time to find an overdue Arctic Loon in the
Pacific Northwest?

2) would one expect to find an arctic loon in a mixed flock with Pacifics?
or by itself?

3) what are the chances of finding one close enough to shore that one might
be better able to scrutinize its markings rather than relying on potentially
misleading field marks like the bird in question. ( in other words, do
Arctics prefer deeper waters?)



cheers,

Don Cecile
dcecile at cln.etc.bc.ca