BIRDS OF PENNSYLVANIA. 
183 
tumn they collect in large flocks before retiring to their winter resorts. 
I have observed birds of this species in Chester county (Pa.), as late as 
the 20tli of October. In this locality the nest of the Chimney Swift, or 
Swallow, as it is mostly called, is composed of small twigs, which are 
glued together and to the sooty walls of disused chimneys with the bird’s 
saliva.* The twigs used in constructing nests are broken off of trees by 
these birds when on the wing. The eggs, four or six in number, are 
white and unspotted. They measure about three fourths of an inch in 
length and about half an inch in width. 
These birds subsist entirely on various kinds of insects which they 
collect during the night as well as in daylight. 
The food materials of twelve birds which I have examined are men¬ 
tioned below: 
NO. 
Date. 
Locality. 
Food-Matekials. 
1 
June 8, 1880. 
Chester county. Pa. 
Beetles and other small-winged insects. 
2 
June 8, 1880. 
Chester county. Pa. 
Remains of beetles and other insects. 
8 
June 8. 1880. 
Chester county. Pa. 
Dipterous insects. 
4 
June 8. 1880. 
Chester county, Pa. 
Fragments of beetles and other insects. 
5 
May 1. 1880. 
Chester county. Pa. 
Beetles. 
(J 
May 1, 1880. 
Willistown, Pa. 
Beetles and small-winged insects. 
7 
June 8, 1883. 
Newark. Delaware. 
Beetles and caterpillar. 
8 
June 8, 1883. 
Newai'k. Delaware. 
Beetles. 
y» 
June 8, 1883. 
Newark. Delaware,. 
Beetles. 
10 
June 8, 1883,. 
Newark. Delaware. 
Beetles and dipterous insects. 
n 
June 2. 1884. 
Chester county. Pa. 
Larvae and flies. 
12 
Aug. 11, 1884. 
Chester county, Pa.. . . 
Dipterous insects. 
Suborder TROCHILI. Hummingbirds. i 
Family TROCHILID^l. Hummingbirds. 
Genus TROCHILUS Linnaeus. 
Trochilus colubris Linn. 
Ruby-throated Hummingbird. 
Description (Plate 56). 
Male. —Tail deeply forked, the feathers all narrow and pointed ; uniform metallic 
green above ; sides of body greenish ; below white ; ruby-red gorget; wings and tail 
purplish-black. 
Female. —Metallic green of upper parts duller than in male ; tail double rounded ; 
its feathers pointed but broader than in male; no red on throat; the tail leathers 
banded with black ; the lateral ones broadly tipped with white. 
Young Male.— Very similar to adult female, but throat more or less streaked with 
dark ; tail also more forked than in female. Nearly all specimens show a trace ol 
metallic red on throat. 
Young Female. —Throat white, without streaks or specks ; tail less forked, other¬ 
wise similar to young male. Irides in old and young brown. Length about 3.25 
inches ; extent of wings about 5 inches. 
* A writer in a recent scientific journal, which I have mislaid, says : “In the case of our own Chimney 
Swifts it has lately been shown that the gelatinous matter with which the twigs are fastened together is 
of a vegetable and not an animal character, and in a particular case recently investigated by a scientist, 
the gum was found to have come from a cherry tree. 
