Posted by Gary Potter (65.160.83.194) on October 08, 2001 at 13:46:10:
This Jaeger is obviously not a Pomerine. The long and narrow wings which are also narrow at the base are more typical of Parasitic or Long-tailed. Also Pomerine should not have pointed central rectrices. Now for the more difficult assessment, is it Long-tailed or Parasitic? Jaegers have tremendous variation in plumage characteristics due to age as well as dark, light and intermediate morphs. The're worse than gulls in this respect! Perhaps structure is the only way to tell for sure. At first glance I thought, what's the problem, it's a Parasitic. Then I looked an some field guides. The NGS guide shows an immature Long-tailed with the head and body pattern of this bird. Can Parasitic also look like this? I'm not sure, but probably. The streaked appearance of the wings leads me to believe that this bird is an immature or juvenile. At this stage the Long-tailed should have blunt tipped central rectrices, with at most very short points. The points on this bird's central rectrices look perfect for Parasitic. The bill looks quite petite, more like a Long-tailed, but the angle of the photo makes a thorough analysis of the bill very difficult. Another point is the shape of the wings. The primaries on this bird seem to form a more rounded posterior margin near the tip which seems to indicate Parasitic. I think that Long-tailed should show a straighter posterior margin to the primaries. Jaegers are often difficult to identify even in the field where several angles of view are possible, so I don't know if this bird can be identified with certainty, but I think, that the majority of its features confirm my original impression. I think that it is a Parasitic, with a confidence level of at least 55%!