No. 21. PENNSYLVANIA STATE COLLEGE. 251 
mature birds are dusky above, more or less spotted with white and 
reddish brown; tail banded and lower parts white, with long brown 
spots. 
Nest building is commonly begun in this locality about the middle 
of April, and lasts for a period of from three to five days. Occa 
sionally this bird will deposit its eggs in a deserted crow’s nest. 
| believe they prefer to erect their own nests, and, from my obser- 
vation, am quite positive they only appropriate the nests of other 
birds when their own have been destroyed. The building of the 
nest is the conjoint labor of both birds. It is usually built in a thick 
woods, and when a pair of Cooper’s Hawks begin housekeeping 
in woodland near the farmer’s poultry yard and they are not soon 
hunted up and killed or their nest and its contents destroyed, the 
chances are they will destroy a good many dollars worth of poultry 
before they and their young leave the locality. 
Iixternally the nest is built of sticks varying much in size. It is 
generally lined with the inner layer of bark, although frequently, 
blades of grass, feathers and leaves enter into the construction of 
the interior. While certain writers have described the nest as 
broad, with but a slight concavity, I have invariably found the con- 
cavities to be well marked. The eggs measure about 1.92x1.50 
inches and usually number from three to four, although it is not a 
rare occurrence to find five. In color they are a dull, bluish-white. 
Sets are sometimes taken with numerous and unevenly distributed 
brown or reddish spots. The period of incubation is given by Prof. 
Thomas Gentry (Birds of Eastern Pennsylvania), to be 18 days. 
Although in this particular my observation has been somewhat lim. 
ited. 1 am fully convinced that the timerequired for this, likewise other 
of our birds of prey, is three weeks or over. The young leave the 
nest in about 25 days; when about 8 or 9 weeks old they are able 
to provide food for themselves; to this time, however, they are care. 
fully guarded by the old birds and fed almost entirely on a diet of 
small wild birds, chickens, an occasional mammal and some few 
insects. 
While if is true that the Cooper’s Hawk preys to a much greater 
extent on full grown poultry than does his daring little relative 
ihe Sharp-shinned Hawk, there is no doubt that at times individual 
Cooper’s Hawks are equally as bad about destroying young pouitry 
as are the Sharp-shinned Hawks. For impudent daring this present 
species, without doubt, ranks preeminent among the raptorial 
genera. Almost every farmer or poultry raiser can recount in- 
stances of where he or she was the victim of pillage by this bold 
and audacious robber. In the spring of I878 the writer was pre 
sented by a friend w ith a Cooper’s Hawk which he had caught in 
