Hi, Jim. I have taken a looksee at the jaeger images posted on the webpage
you indicated and have come to a conclusion. References: relied heavily
on the excellent "Jaeger Migration on the Great Lakes" by Dominic F. Sherony
and Kenneth A. Brock in _Birding_, Vol. 24, No. 5, October 1997 issue. Also
Kenn Kaufman's _Advanced Birding_ (1990).

Of the six photos, three show diagnostic field marks for Parasitic Jaeger:

Photo 2 - Great shot of at least 6 white primary shafts. This rules out
Long-tailed but not Pomarine. However, Poms never have the long
skinny central tail projections shown by this bird.
Photo 4 - Good inflight view of relative size of the chord of the wingbase
compared to the length of the tail (not counting streamers).
In Long-taileds, the tail is longer than the wingbase is wide;
they are about equal in Parasitics; and the wingbase is obviously
deeper in Pomarines. Looks about equal to me.
Photo 6 - Excellent shot of the pale buffy spot at the base of the forehead
above the bill which is diagnostic for Parasitic.

..and in all photos, "hook" on end of bill consistent with Parasitic but
much too weak for Pomarine.

As for ageing this bird, it is either a winter-plumaged adult (which N.
Americans rarely see), or a sub-adult needing one more molt for definitive
alternate.

cheers,
Jack



Jack Bowling
Prince George, BC
jcbowling at mindlink.bc.ca

cc: Tweeters <tweeters at u.washington.edu>