210 
CHJETURA PELASGIA. 
for example, when sailing in a direct line or moving in large circles, they glide through 
the air so easily and so smoothly that no one would accuse them of awkwardness; in short, 
they fly so well that a certain heaviness which is only perceptible upon comparison with 
the light, almost ethereal, movements of the Swallows, is quite over-looked and one is 
never tired of watching the characteristic and unwearied flight displayed by the Chimney 
Swifts. When the birds are sailing, flying in a direct line, or wheeling in immense cir¬ 
cles, the tail is closed but when a sudden turn is made, then it is expanded and is also 
opened when the birds wish to check their flight. Unlike the Swallows, they do not move 
in particular strata of atmosphere in different days but, while soaring high in air, will often 
come plunging downward and fly along within a few feet of the ground. They have a 
habit of darting close to any one and will repeatedly persist in so doing. I have known 
of quantities being killed by boys who stood on a bridge and struck them down with sticks 
as they passed. I have been informed by good authority that these birds will sometimes 
mount in air, then form a circle by closely following one another and continue to fly in this 
manner for some time. 
I never saw the Chimney Swifts alight and do not think that they ever settle outside 
the chimneys. Even when gathering material with which to construct their nests, they 
do not rest on the trees but will fly through the dead branches and break off the small twigs 
as they pass, grasping them with their beaks. These Swifts are among the birds, the 
breeding habits of which have become decidedly modified by the innovations of man. They 
doubtlessly nested in hollow trees before the advent of the whites but now they always 
breed in unused flues of chimneys. As soon as they arrive, they occupy their usual quar¬ 
ters at night and soon begin to build. At this season, the glands of which I give a figure 
in plate XIII, are enlarged and secrete a viscid substance which, for convenience, we may 
call saliva yet it bears but little resemblance to this secretion as it is usually found. This 
saliva is poured forth abundantly during the time of nesting and is used to cement the 
twigs together. As seen by the figure of the tongue in the plate, this organ is of a some¬ 
what peculiar shape and is doubtlessly used as a kind of trowel which it resembles in form, 
to spread the cement upon the twigs. This viscid substance is milky white in color when 
first exuded, but becomes yellowish and nearly transparent when dry. It is of the con¬ 
sistency of bird-lime when first applied and must harden quite rapidly. The birds evidently 
are obliged to exercise care while at work in order to prevent their feathers from being en¬ 
tangled, but this occasionally occurs and it is not unfrequent to find feathers fastened to 
the nest. Both sexes are provided with these glands which rapidly shrink after the breed¬ 
ing, season and are scarcely discernible by the time the young are hatched, the space that 
they occupied being used as a kind of pouch in which insects are packed when they are cap¬ 
tured. I have seen the birds when this cavity was completely filled with minute insects 
that were intended for‘the young. 
I think that these glands are peculiar to the Swifts as I never observed them in nny 
other species, not a trace of anything of the kind being found in any of our Swallows 
that I have examined. As the cement secreted by the glands of the Swifts is soluble in 
water, the nests frequently become detatched during storms and fall to the bottom of the 
