Hi. This is Daniel Bastaja posting for Sunday, January 4th, 2004. Happy New
Year everyone!



During the late fall and early winter, the Danube River and other large
bodies of water in Hungary (Lake Velence, Lake Balaton) host small numbers
of Arctic Loons. I have had a chance to observe several of these birds over
the last couple of months and I thought I would share my impressions with
birders on the West Coast of North America. Please keep in mind that all the
observations are of the Western Palearctic (ie: European) subspecies (G.a.
arctica) which is not the subspecies most likely to be seen in North
America. Nonetheless, some of these comments may be helpful for birders
trying to separate this species from Pacific Loon in the field.



Here is a link to several photos. Once you click on the link, scroll down to
?Arctic Loon Gallery? and you will be able to view 29 digital snaps
depicting 7 individual birds.



http://www.birdingfaqs.com/hungarianbirds/



In an earlier posting to some of the chat groups, I questioned the
importance of the famous white flank patch. I retract those comments. After
seeing more individuals, I realize that it IS a good field mark
.I just don?
t feel it?s diagnostic. It is more of a confirmatory feature, or a feature
that may draw your attention to a particular loon for more detailed
inspection. But the amount of white showing on the lower flanks varies a bit
between individual birds and also how low the bird is riding in the water.
Photos # 12 and # 14 will show you what I mean. Moreover, in British
Columbia I have seen Pacific and even Common Loons showing a lot of white on
the flanks. So you have to be very careful when it comes to this particular
field mark.



Therein lies the nub of the problem with Arctic Loons. From what I can see
there really isn?t ANY truly diagnostic field mark to easily confirm the
species in the field. It?s more of a combination of subtle characteristics
that together make an ID. If that doesn?t make it tough enough, it is
complicated by the fact that I have seen exceptions to just about every
characteristic. So it ain?t easy.



Other than the white flank patch, here are some of the field marks I have
noted.



1. Physique



Heavier set bird than a typical Pacific Loon. The bill is noticeably larger,
the head tends to be somewhat bigger, and the neck tends to be thicker.
Check out pics # 6 & 7 and you will see what I mean by a thick neck
(although this bird had a bit thicker neck than most). Pic # 17 shows you,
with that big barrel chest out of the water, just what a chunky bird it is.
At a distance, and without direct comparison, it could even be passed off as
a Common Loon by a cursory observation. This may be more likely with the
Siberian subspecies (G.a. viridigularis) because it is supposed to be even
stockier than the European subspecies.



2. Shape of head



The head shape varies but the most reliable feature seems to be a flat spot
across the crown. There is usually a bump on the front of the head followed
by the flat spot, but sometimes the bump can be at the rear of the head.
Occassionally a bird will have a bump at front and back, and sometimes no
bump at all but just a subtle angle. Every bird I saw, though, had some kind
of irregular head shape
it was never completely smooth and rounded. Even
this, though, is possible. Photo No. # 12 shows one bird with a smooth,
round head. This head shape is an exception though
.maybe because the bird
was in an alarm/reconnaissance posture. Photo No. # 29 also shows a bird
with an almost perfectly smooth head
.just the subtlest of angles at the
back. The majority of birds though, have the lumpy, bumpy or angular head
shape. Pic # 19, with three birds in line like mini-battleships, provides a
good comparison. The middle bird has a small bump on the front of the head
and smooth at the back, while the other two have no bump in front but a
noticeable angle at the back. All three birds display that characteristic
flat area at the very top of the head.



3. Angle of head/ beak



At rest, the head and beak are held up at a very slight angle. Not as much
as a Red-throated or Yellow-billed Loon
.more subtle than that
..but still
noticeable. I did encounter one individual that spent periods of time with
it?s head and beak virtually horizontal (see pics # 24 & 25) but then at
other times it would revert to the classic tilt (pic # 22, 26 & 27). Pics #
28 & 29 show another bird that is holding it?s beak virtually horizontal
but, once again, this is unusual. The slight tilt is by far the norm.



4. Colouration of neck and head



The grayish colouration on the head and neck was sometimes uniform but more
often it wasn?t. It tended to be paler on the back of the head and neck and
somewhat darker at the the sides, especially at the line of demarcation
between the grey and white at the side of the neck. Also tended to be darker
at the lores. The contrast seems to be much more pronounced on juvenile
birds and more subtle on adults. Pics # 22, 23 & 24 shows this contrast on a
juvenile bird quite well
.darker at the leading edges and paler at the back.
You can also see by these pics that the juvenile birds often have a brownish
cast to the grey.



5. Sharpness of colour transition



Although it varies among individuals, the line of demarcation between grey
and white along the neck and head is generally not as sharp as on a Pacific
Loon. It tends to be somewhat fuzzy or blurred, much more so on juvenile
birds than on adults. Every bird showed a contrast between the neck and head
and a darker body although the contrast again seemed to vary between
individuals. And, once again, this contrast seemed to be the greatest with
juvenile birds. When viewed through the binoculars at a distance I often got
the impression of a loon with a dark body and pale head and neck.



6. Chin-strap



Rather than a line across the top of the neck underneath the chin, I often
saw a subtle line across at the base of the neck. Not on every bird, but
many had this. You can see this subtle line at the base of the neck quite
well in pics # 16, 17 & 18. I encountered just one individual that had not
only the subtle line at the base of the neck, but also one across the top of
the neck underneath the chin. You can see this most clearly in pics # 23, 26
& 27. Yes
unfortunately it appears that even the ?chin-strap? thing is not
an airtight field mark. But I think this is the rare exception on the odd
juvenile bird, and it is more of a linear smudge rather than a sharp line.



7. Cheek



On many birds I got the impression of a more ?scooped-out? white cheek
compared to a Pacific Loon. The white extends inward below the eye and then
the grey at the side of the neck forms a point near the top of the neck,
forming kind of an oval cheek patch. This wasn?t on every bird, but many had
this. It is a subtle thing
.maybe it seems more pronounced than on a Pacific
Loon just because the Arctic?s head is bigger
.or it could be that the grey
?point? at the side of the neck is somewhat more pronounced.



Conclusions (please keep in mind that the following is just my personal
opinion):



There is no one, or even two field marks that are conclusive. There are
perhaps eight or ten individual points to distinguish an Arctic Loon, and
the bird you are looking at really should have a minimum of 75% to 80% of
those points to be considered an Arctic.



While I saw exceptions to every field mark that is supposed to separate
Arctic from Pacific, the exceptions are rare, and no single individual bird
had ALL the exceptions.



Juvenile birds should be a lot easier to positively ID than adults.



Direct comparison in the field is an absolute Godsend. If an Arctic is in
company with Pacifics, ID will be much, much easier. Preferably in company
with Pacifics but even if the bird is with Common Loons, it should still be
easier than if the bird is by itself.



Overall impressions may be helpful. I can itemize 6 or 8 or 10 individual
field marks, but the combined effect of all these things creates an
impression of something ?different?. You might be looking at a loon that
doesn?t look quite right for a Pacific, yet it doesn?t look right for a
Common Loon either. You know what I mean? Just something that looks odd or
different. If you are used to seeing Pacifics and Commons year in, year out,
an Arctic will likely give you that feeling in your gut. Kind of like
.?What
the heck is this thing?? Of course you can?t base an ID on such things but
it is useful for drawing your attention to a particular loon that deserves
much closer scrutiny.



Definitely one of the tougher IDs out there. Good luck!!



Regards,

Daniel Bastaja

Budapest, Hungary

dan at calivita.com