jaeger


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Posted by Phil Pickering (208.46.229.203) on October 23, 2001 at 11:00:04:

Time for my daily post on this bird.

Post-juvenile generations of central tail feathers may be more pointed in Long-tailed, but does any resource, photo, or anyone's experience indicate that they can show a shape like this when they are this short - with such an inwardly-angled taper to the base of the projecting section, and a pronounced break in angle of taper forming a narrower, straighter, very sharp trailing tip? Since this shape seems to be typical of immature Parasitic, I think this is one of the most important questions raised by this bird.

Since the shape of the R1s is so fundamentally different between juvenile Parasitic and Long-tailed, I have to wonder if there aren't likely to be appreciable differences in the shape of these feathers in proceeding generations. Even mature, definitive alternate Parasitic R1s often seem to show a more inwardly-tapered section, or inwardly-angled curve somewhere near the central part of the projecting section of the feather, leaving the section trailing the break in angle of taper very fine and sharp out to the feather tip. To state this concisely, there are, at least often if not always, visible changes in the angle of taper along the outer edges of the projecting sections of the R1s in Parasitics, even adults.

I've tried, and have so far been unable to see this in photos of definitive alternate Long-tailed. The projecting sections of their R1s seem to most typically have fairly straight outer edges throughout their lengths, without a noticeable break in angle of taper. Perhaps a break in angle may just be less apparent because the R1s are so much longer in Long-tailed, but it doesn't ever seem to be obvious, as it is in many Parasitics.

Since BOTH juvenile and (apparently) adult Long-tailed have such straight outer edges to the R1s, is it possible that the break in angle of taper I've noticed in immature AND adult Parasitic is a fundamental difference in the shape of these feathers that might be apparent to a varying degree at ALL ages? I'll happily accept it and shut up if someone can point out that the situation is otherwise, but I thought this was at least potentially important enough to risk speculating about, even though I've already hogged too much air time on this bird.

Cheers,

Phil



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