[birdky] Mystery Bird Solution

From: Mark Monroe <markmonroe1@xxxxxxxxx>
To: BIRDKY <birdky@xxxxxxxxxxxxx>
Date: Mon, 20 Apr 2009 22:54:25 -0400
The mystery bird posted a few weeks ago at
http://www.biology.eku.edu/kos/whatisit.htm was certainly one of the harder
ones to date.

I've asked Jon Dunn, author of *Field Guide to Warblers of North America*,
to provide the solution to this quiz bird.  Without further ado:


Ugh, a mystery photo of a little brown job, the classic LBJ and your worst
nightmare.  But before you give up consider the time and place.  It's late
July and you are in eastern Kentucky.  With few exceptions, the passerines
you see there will be local breeders.  So, being familiar with the local
breeding birds there should immediately narrow the options.  This bird shows
traces of the pale gape line indicative of young immaturity and typically
seen on or close to the breeding grounds.  Often the adults are still
feeding birds of this age, so it might be worth waiting for one of the
parents to visit with food.  That would offer a big clue.  But let's assume
it's fledged and is completely and on its own.  This a rather slender
passerine with a long notched tail.  It is brownish above with two pale
wingbars and from what we can see is whitish and unmarked below.

When considering the breeding species, what about a juvenile Indigo
Bunting?  The overall coloration is about right, but that species would have
a shorter tail and would also show blurry streaks below.  And the bill is
not a finch bill, it's too petite.  With the finer bill, one should consider
the various warbler species that breed in eastern Kentucky.  Though the bill
is more petite than a finch, it is still rather thick for most warblers,
although it does fit well within a few of our *Dendroica* species.  This
large genus includes many species that look quite different between spring
and fall, or look differrent depending on the age or sex.  But really only
plumage of a *Dendroica *fits this bird and that's an immature female Pine
Warbler and Pine Warblers are rather large billed. Since it is unmarked
below, I assume it's molted out of its juvenal plumage.  A useful feature
for Pine Warbler in ANY plumage is the fact that the auriculars contrast
darker to the pale chin and throat.  Brighter Pines can be confused with
fall Bay-breasts and Blackpolls, but they have more blended auriculars and
also are much shorter tailed.  Pine appears longer tailed, indeed it has
longer tail extension past the undertail coverts than any other *Dendroica*.
Well, we can't quite see the undertail on this bird, nor the tail spots
present on the outer tail feathers.  On the folded tail, the tail pattern,
including tail spots have to be seen when viewing the ventral side of the
bird.  If we had seen those, it would have been easier to place the bird in
the wood warbler family and probably in the genus *Dendroica*. From above we
see only central tail feathers and those offer few clues in identifying
passerines.  So, always try to see the underside of that tail.  One other
feature we would see on fall Bay-breasts and Blackpolls are distinct whitish
tertial edges.  These are lacking on Pines.  Keep in mind that no Bay-breast
or Blackpoll would be in eastern Kentucky in late July, or even until
late August, and Blackpoll is rare in Kentucky at any time in the fall
(passage southeast occurs farther north, south in numbers only to the
southern Great Lakes).  Other species to consider would include Prairie
Warbler, but that species always has yellow underparts, even the drabbest
immature female, and has a pale sub ocular crescent.

Sexing immature Pine Warblers after the post juvenal molt is reasonably
straight forward.  Both sexes look brownish above, but males have olive
mixed in and are extensively yellow below.

This immature female Pine Warbler was photographed near Red River Gorge,
Menifee County on 31 July 2008.


Thanks again to Jon Dunn for the write-up.

Mark Monroe
Louisville, KY
[birdky] Mystery Bird Solution

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