TRAILL'S FLYCATCHER Complex— 
WILLOW FLYCATCHER (Empidonax traillii) 
ALDER FLYCATCHER (Empidonax alnorum) 
(Fig. 32 and 33) 
Spring Migration 
Determining the migration patterns of any 
Empidonax flycatcher is difficult because of the 
identification problems. The Traill’s flycatcher complex 
ey 
Fig. 32. — Traill’s flycatcher at its nest. Like other Empidonax, Traill’s have a light eye-ring and whitish wing bars. 
36 
is even more complicated than the rest, because the ty 
species are so nearly identical. | 
The most distinctive characteristic of the two is ¢! 
song, often phoneticized “fitz-bew” for the willc 
flycatcher, and “fee-bee-o” for the alder flycatche 
Morphological characteristics of the two forms over; 
greatly, and even with specimens in hand we have be: 
uncertain about identification of some specimens. T] 
dependence on the birds’ singing for identificati 
complicates the study of migration of the two forn 
A i 
