From: Bob Fisher <[log in to unmask]>
To: [log in to unmask]
Sent: Sun, September 19, 2010 9:10:28 PM
Subject: Jaeger ID and the Jaeger is ...
Tim, Josh, Doug and now Kristi herself have opined that the Smithville bird is a Parasitic. Let me make the case for Long-tailed Jaeger using Kristi's photo. Perhaps it will help folks taking the pelagic trip tomorrow know what to look for.
First of all, we have a great photo to work with. Here are some comments re what can be seen on the photo:
General comment: Kristi's bird is a light morph juvenile of whatever species it is.
Head color: The bird has a pale head, which is characteristic of first year Long-tailed Jaegers.
Bill size: The bill appears to compare satisfactorily with LTJA bills.
See e.g. http://www.kayniyo.com/images/trip_alaska_2003/658LongtailedJaeger3702.jpg
Parasitic's have bills that are longer in proportion to their thickness. See e.g. http://bkpass.tripod.com/PAJA62903BR.jpg
Nape markings: According to Sibley, Parasitic has a streaked nape. See e.g. http://www.focusonnature.com/BirdLi757.jpg LTJA has an unpatterned nape. The Smithville bird's nape looks unstreaked.
Feather edgings: Both species have pale feather edgings, but Sibley describes Parasitic's as "buffy feather edges" and LTJA's as "usually obvious pale feather edges". Kristi's bird has pale, but not buffy, edges.
General plumage coloration: Kristi's bird fits Sibley's "Juvenile cold grayish" for LTJA versus "Juvenile usually has obvious cinnamon tones in plumage" for Parasitic. See e.g. the cinnamon tones in PAJA depicted in http://www.birdzilla.com/images/stories/lavaty/parasitic-jaeger.jpg
White in primaries: Kristi's bird has very little white in primaries, as one would expect of LTJA. Parasitic should have a lot more.
See e.g. http://lh3.ggpht.com/_E5uf0AiTz0k/SHLFK0eRyvI/AAAAAAAABm0/9g5ctjQrwfQ/DSC06804.JPG
Careful examination of Tim's, Josh's and even Kristi's revised ID disclose a lot of subjective stuff (e.g. "bulky bird, not slender looking") from people who see Jaegers only very rarely.
There is one mark favoring Parasitic that Kristi's first photo may show, but which cannot be seen in the more recent photo. The central tail feathers of a juvenile Parasitic should be pointed. Those of a LTJA should be blunt. I'll be looking for those tomorrow.
The Audubon Society of Missouri's Wild Bird Discussion Forum
Questions or comments? Email the list owners:
mailto:[log in to unmask]