192 
YELL O W-BELLIED EL YCA TCHER. 
ground. Alder swamps which are so filled with undergrowth that it is difficult to force 
one’s way through them, are the favorite resorts of these Flycatchers. It is extremely 
difficult to detect the presence of these little birds in such places, not only on account of 
the luxurious vegetation, but principally because they are extremely quiet, the only note 
which they utter during the migrations being a plaintive pea given only at intervals and, 
so low as to be inaudible a few yards distant. I have frequently entered a swamp in 
which I was certain some of these Flycatchers had taken refuge and have, at first, been 
unable to find a single specimen, but upon remaining quiet for a moment, I would hear the 
low peas in all directions. Guided by the sound of the nearest, I would proceed cautious¬ 
ly in its direction and, after a moment’s search, would see the bird as he sat on some low 
twig, occasionally launching outward for a short distance to catch a passing insect which 
his keen eye had informed him was especially palatable. As long as I remained perfect¬ 
ly still, the Flycatcher would pursue his vocations but upon my making the slightest 
movement, he would observe me and, giving a quick, upward flirt of his tail, would flit 
silently but with marvelous celerity among the brown stems of the alders, and skillfully 
wending his way through the labyrinth of twigs, vines, and leaves, he would almost in¬ 
stantly disappear. 
Although the Yellow-bellied Flycatchers are not sluggish birds, yet when compared 
with the allied species, they appear somewhat inactive. This is due, however, to the fact 
that there is but little need of them leading a bustling life. The orchards which are the 
chosen domains of the Least Flycatchers are also the resorts of hundreds of other birds and 
consequently the Flycatchers must keep wide-awake in order to gain a livelihood and—they 
do it, as I have endeavored to show. Traill’s have a less disputed field but still there are 
enough other avian inhabitants of the locality in which they find a home to make insects 
tolerably scarce, so these birds cannot be idle; while as I have already described, the Aca- 
dians usually live in localities where many species of the feathered tribe are abundant. 
With the birds under consideration, this is quite different for they occupy spots where but 
few others occur and where insects abound; thus they are not obliged to lead a very active 
life and therefore their habits have become decidedly modified by the circumstances in 
which they are placed. 
The lives which the members of this genus lead have apparently had some effect upon 
their physical organization. Thus we find that the Least Flycatcher is not only the best 
flier, but it also has the best development of laryngeal muscles, consequently has the most 
variety of notes, it being understood, however, that this partial development does not al¬ 
ways mean that the voice of their possessor is the most musical. Next in order follows 
Traill’s, differing but slightly from the one last described, and then comes the Acadian 
with weaker laryngeal muscles, for the broncho-trachealis is but slightly developed and 
consequently the twittering notes are given less frequently than by the two preceding; 
last in the list comes the Yellow-bellied Flycatcher. The low and slowly given pea and 
a gravely rendered ke-lick , the first as a single note and the second repeated only at long 
intervals, are the only sounds which I ever heard them utter for they make no attempt, at 
the twittering song. I was not surprised, therefore, when, upon examining the larynx, I 
