BIRDS OF PENNSYLVANIA. 
183 
tumn they collect in larg-e flocks before retiring to their winter resorts. 
I have observed birds of this species in Chester county (Pa.), as late as 
the 20th 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 disusedchimneys 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-Materials. 
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. 
;i 
June 8. 1880 
Chester county. Pa 
Dipterous insects. 
4 
June 8, 1880, ..... 
Chester county. Pa., 
Fragments of beetles and other insects. 
May 1, 1880 
Chester county. Pa 
Beetles. 
li 
May 1, 1880 
Willistown, Pa 
Beetles and small-winged insects. 
T 
June 8, 1883 
Newark, Delaware, 
Beetles and caterpillar. 
8 
June 8, 1883 
Newark. Delaware, 
Beetles. 
1) 
June 8, 1883 
Newark. Delaware, 
Beetles. 
10 
June 8, 1883, 
Newark. Delaware, 
Beetles and dipterous insects. 
11 
June 2, 1884, 
Chester countv. Pa 
Larvae and files. 
12 
Aug. 11, 1884, 
Chester county. Pa 
Dipterous insects. 
Suborder TKOCHILI. HuMMmoBTRDS. 
Family TROCHILID.®. Hummingbirds. 
Genus TROCHILUS Linnjeus. 
Trochilus colubris Linn. 
Ruby-throated Hummingbird. 
Description {Plate 56 ). 
AfaZe. — Tail deeply forked, the feathers all narrow and pointed ; uniform metallic 
green above ; sides of body greenish ; below white ; rnby-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 feathers 
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 of 
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 Avings about 5 inches. 
* V writer in a recent scientific journal, which 1 have inisiaid, 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. " 
