Hi. This is Daniel Bastaja posting for Monday, March 1st, 2004



In a previous posting about Arctic Loon ID, I mentioned that the chin strap
did not appear to be an ?airtight? field mark of a winter Pacific Loon. I
based this comment on a single personal observation of a first winter Arctic
Loon that had a smudgy line underneath the chin.



Thanks to members of the Eurobirdnet chat group, I have managed to secure a
raft of new photographs for my Arctic Loon Gallery and these pics show two
other juvenile Arctics with the same characteristic.



Here is the link again. Click, then scroll down to ?Arctic Loon Gallery?.
The 16 fresh pics are numbers # 30 though # 45.



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



Through observation, photos and discussions with members of the group, I can
offer some conclusions about the chin strap thing (at least as it relates to
the European subspecies of Gavia arctica):



- winter adult Arctic Loons generally never have a chin strap BUT

- the occassional first winter bird can have a weak chin strap.

- the chin strap usually appears as a faint, linear smudge BUT

- it appears darker when viewed from the side than when it is viewed
head on, AND

- certain light conditions and postures can make it appear darker
and more definitive.

- as only juvenile Arctics appear to show this feature, it follows
that a ?strapped? Arctic should also have the light and dark scaly or
scallopy back pattern of a juvenile bird.

- if a bird has a chin strap and an adult back pattern (at close
range - fine dark-on-dark scales
.at distance ? uniform dark) then it is
likely a Pacific Loon.



Have a look at photo # 30. How many of us, seeing this image through our
scope on Georgia Strait or Puget Sound, would have, because of the chin
strap, immediately passed this bird off as a Pacific Loon? I know I probably
would have. Photo # 33 is another example how the smudge can look more
definitive at certain angles and light conditions.



As I mentioned in my previous posting, the presence of, or absence of any
one field mark, be it white flanks or chin straps, is, in my opinion,
absolutely not conclusive. It?s the combination of characteristics that
counts. You can?t bake a cake with only one ingredient.



Regards,

Daniel Bastaja

Budapest, Hungary

dan at calivita.com