It's probably also worth noting that while Pyle was justifiably
cautious in the 1987 version of IGNAP by the publication the
more comprehensive 1997 edition he had this to say:

" Thus, successful identification of Alder and Willow flycatchers
in the hand involves a synthesis of plumage characters, measurements,
and wing morphology by age, sex, and geographic variation, and the
use of a buffer zone in which birds should be left unidentified.
Brown or grayish birds with indicative measurements (Table 4,
Fig. 149) are identified reliably as Willow Flycatchers, whereas
uniformly greenish birds with relatively bold wing-feather edging
only should be identified (by in-hand criteria alone) if their
measurements fall outside the buffer zone (Fig. 149, Table 4)."

And those that can't be identified? That's right the Feds want
them reported as Traill's...


> Pyle et al. in "Identification Guide to North
> American Passerines" (1987) caution that the two probably cannot be
> safely separated by in-hand criteria alone. It takes a combination of
> a bill measurement and a wing-formula ratio to reliably separate 95%
> of birds, and even then, some were misidentified, based on song type.
>

--
Mike Patterson
Astoria, OR
celata at pacifier.com

A child who becomes acquainted with the birds about him
hears every sound and puzzles out its meaning with a cleverness
that amazes those with ears who hear not.

-Neltje Blanchan

http://www.pacifier.com/~mpatters/bird/bird.html