bluebird primary extension

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Posted by Jim Tietz (24.4.254.108) on March 09, 2000 at 00:40:01:

I mostly want to comment on bluebird primary extension. On my screen, I can clearly discern at least 6 (possibly 7) primary tips beyond the tertials. The first three past the tertials have short distances measured from the tip of the above (or inner) feather to their tip. The 4th has a medium length. The 5th one is quite long: at least twice the length of the preceding feather. And the last one clearly visible (#6) is another medium. There is probably a seventh tip with the sixth, but it is not crisp enough there to be certain. The last two obvious primaries appear to extend past the upper-tail coverts and about half to two-thirds down the tail, but with the angle of the bird, it is difficult, if not impossible, to be certain. If these last two are difficult to see, possibly it is because they are above the tail against the dark background.

Also, if you ratio the length of the exposed tertials to the exposed primaries, it is about 2:3. Meaning that the tertials equal 2 units and the primaries equal 3.

The main point for writing this is to find out if anybody knows if bluebirds can be identified by the spacing distances of primaries, or whether they can be identified by comparing tertial length to primary length. My personal opinion is that this bird is a MOBL based on the long primaries, but what do I know, I have seen MOBL only a half dozen times. I will have to look at some WEBL primary ext. for comparison.

I have also thought that the thrasher is a Bendire's based on the pale base to the bill and the rather straight lower edge to the mandible. I wonder though about the head shape. From the Master Guide photos, doesn't it appear that Bendire's has a rounder head than Curve-billed? I have no personal experience with this though, and the flat head on the quiz bird could be do to feather flattening. Lastly, how does tail tip pattern figure into this identification? Would the white tail tips on the quiz bird be considered conspicuous like on a Bendire's or more indistinct as the western race of Curve-billed should show?

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Re: bluebird primary extension Tony Leukering 23:54:30 03/14/00 (0)

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: I mostly want to comment on bluebird primary extension. On my screen, I can clearly discern at least 6 (possibly 7) primary tips beyond the tertials. The first three past the tertials have short distances measured from the tip of the above (or inner) feather to their tip. The 4th has a medium length. The 5th one is quite long: at least twice the length of the preceding feather. And the last one clearly visible (#6) is another medium. There is probably a seventh tip with the sixth, but it is not crisp enough there to be certain. The last two obvious primaries appear to extend past the upper-tail coverts and about half to two-thirds down the tail, but with the angle of the bird, it is difficult, if not impossible, to be certain. If these last two are difficult to see, possibly it is because they are above the tail against the dark background. : Also, if you ratio the length of the exposed tertials to the exposed primaries, it is about 2:3. Meaning that the tertials equal 2 units and the primaries equal 3. : The main point for writing this is to find out if anybody knows if bluebirds can be identified by the spacing distances of primaries, or whether they can be identified by comparing tertial length to primary length. My personal opinion is that this bird is a MOBL based on the long primaries, but what do I know, I have seen MOBL only a half dozen times. I will have to look at some WEBL primary ext. for comparison. : I have also thought that the thrasher is a Bendire's based on the pale base to the bill and the rather straight lower edge to the mandible. I wonder though about the head shape. From the Master Guide photos, doesn't it appear that Bendire's has a rounder head than Curve-billed? I have no personal experience with this though, and the flat head on the quiz bird could be do to feather flattening. Lastly, how does tail tip pattern figure into this identification? Would the white tail tips on the quiz bird be considered conspicuous like on a Bendire's or more indistinct as the western race of Curve-billed should show?

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