Update: I had forgotten to mention calls: there were a
number of standard "whit" type calls coming from the
tree - some more emphatic than others, plus an occasional higher-pitched
"peep" - but it was impossible to assign any call to
any particular individual bird.
These empids were present in my yard in western Fort Worth on
September 5, 2003. There had been a major drop-in of birds (with
six species of vireo and seven species of warbler) that included
many empids and other Tyrant flycatchers. There is a small patch
of fruiting shrub below this tree, and the empids and vireos were
regularly working it for insects and also taking the small berries
(I saw at least three different Empids do this.) I was positioned
c. 20 feet away with bins, 'scope and digital camera, and watched
the "procession" for about 90 minutes. It is impossible
to say how many different empids were involved, but most seemed
to be Least, with one or more Yellow-bellied and one Trail's.
Almost all the birds seemed to be juvs (fresh, well-marked coverts
and flight feathers; generally more yellowish tones below.)
1) Least or Yellow-bellied?; does the primary tip spacing allow
it to be ID-ed?:
2) I had presumed this to be a Yellow-bellied, but I am puzzled
by how many features seem to match Western:- the most obvious
is the eye-ring shape - but some Yellow-bellied and Least can
be like this; the length of the tail seems too great for Yellow-bellied
and Least; the ground color of the primaries is brown, not blackish
(compare to bird above) and the tertial fringes are rather weak;
in view through the telescope the contour feathers were more worn
than on the other juv. Empids (seen with same conditions/distance)
- this wear is visible in the pics in the scapulars; most Empid
juvs molt their contour feathers on the breeding grounds, but
Western juvs perform this molt much later, on the wintering grounds,
such that there may be a visible (with good looks) difference
in the amount of wear in these feathers. Obviously the major problem
with calling this a Western is the lack of a visible crest (in
the field this bird's head shape looked "standard" empid
shaped) - can Western ever look like this?:
3) This one looked like a Trail's in the field; note the long
primary projection:
4) I feel that this is a typical Least; note the short tail:
