2 
and key. Many of the Vireos, conspicuously the White-eyed, “sing” 
their regular song as an alarm-cry when the nest is approached. Of 
course all those birds that have but a single cry may utter this on occa¬ 
sion of excitement of any kind. It does not seem likely therefore that 
the songs of birds during the mating season indicate any such purely psy¬ 
chical phenomenon as affection or joy, that is, of a rational or mental 
character. In fact, the excitement that calls forth the song at this time 
is in a large measure physical. During the mating period the bird is phy¬ 
sically more active than at any other season of the year. This activity is 
manifested in various ways—by superior energy of movement, great pug¬ 
nacity, perfection of coloration, and chiefly by sexual excitement; on their 
last in fact, the other manifestations of activity are more or less depend¬ 
ent, and it is to this also that the song is due. The reproductive instincts 
are now predominant and their natural expression is largely through the 
vocal organs. No doubt the song of the male bird is attractive to the fe¬ 
male in proportion to its perfection ; not however from any aesthetic sense 
on her part, but only as it indicates physical vigor. It is one of the finer 
properties of her reproductive instinct to choose the most vigorous male as 
the parent of her offspring. 
Furthermore, this theory, that the song in the mating season is merely 
the expression of sexual activity readily accounts for the fact that a se¬ 
cond period of song precedes the deposition of ^a second set of eggs, 
whether the species normally rears two broods in a season, or the first set 
of eggs is destroyed and is replaced by a second. In either case sexual 
excitement is renewed, though, as we would naturally expect, to a less de¬ 
gree than at first, and the song is proportionately feebler and i^s period of 
continuation shcrter. 
It is well known that many species of birds will remain inactive for a 
lohger or shorter period after a nest has been broken up, uttering peculiar 
amd ;often plaintive cries, which are usually supposed to be expressions of 
grief or regret over the loss. It is noticable however that these cries are 
usually the same as those emitted when an individual has become bewil¬ 
dered or lost during the migrating season, or is accidentally separated 
from the fleck if the species is gregarious. The cause in both cases is 
doubtless much the same, and, though psychic in its nature is of a low 
and simple psychic order. It is iherely that an instinct has been inter¬ 
rupted in its operation, the bird is at a loss what course to follow, and a 
species of mental 'Excitement ensues which must find some vocal expres¬ 
sion and which continues till the normal order of things is resumed. In 
the one case it is the migratory or gregarious instinct that has been inter¬ 
rupted, in the other the reproductive. 
The sharp cries uttered by small birds on perceiving an individual of 
some perdatory species do not indicate any such complex psychic phe- 
