45S 
ECONOMIC RELATIONS OF OUR BIRDS. 
their services are much needed. The Quail and Prairie Chicken are also largely 
insectivorous until after the middle of August, when the grain is harvested and 
out of danger from them, and as they hve in uncultivated fields and meadows 
their services are very valuable. 
(17) ^Vllether the bird is or is not a necessary habitat for troublesome parasitic 
entozoa. As many fishes are infested with parasites, some of which pass 
through one stage of their development in Herons and other piscivorous birds, 
it becomes a question worthy of study to determine whether these birds may 
become detrimental to fish-culture by breeding parasites which will destroy the 
fish or render their flesh unfit for food. This question is the more important 
since fish-culture has become a national enterprise. 
(18) The number of broods the bird rears each season. Those birds which rear 
more than one brood during the season, if they are not injurious, are likely to 
be of greater service than those which are single-brooded, not only because they 
must be more destructive to insects directly, but because they are capable of 
becoming more numerous than single-brooded species are likely to become. 
OTHER CONSIDERATIONS. 
(1) The changing habits of birds. Two hundred years have been sufficient to 
produce such marked changes in the habits of many American birds as to have 
caused them to assume entirely new relations to human interests. In virtue of 
these changes many birds have become more useful, some have become more 
injurious. Many, like the Swallows, now build their nests in situations whose 
surroundings are so entirely different’ from those of their original haunts that 
the character of their food must have undergone quite as marked a cliange as 
have the situations in which they build their nests. Since all of our native birds, 
which are so familiar about dwellings and farms, once inhabited exclusively’ 
wild tracts, it is but fair to presume that many which are now shy and retiring 
will in time become as confiding as those which have already taken uid their 
homes with us. Indeed, these changes are being noted almost every year. 
When these changes of habits do take place, with them must come new and 
important relations. Some of these birds will then be more useful, others may 
be more injurious. The practical question arising from this is, how can w’e best 
hasten these changes ? 
(2) Can birds ever become abundant in thicldy settled districts ? The facts 
which have thus far been recorded in regard to the abundance of different 
species of birds in different localities at different times, are so meager and in¬ 
definite, that it is impossible to draw any very satisfactory conclusions in regard 
to this point at present. To throw some light upon this question the statistics 
on page 447 have been prepared. They are too limited to be of very great 
value by themselves, and are offered here simply as a beginning. The two 
localities in which the statistics were taken are not as similar in some respects as 
could have been wished. Due allowance must be made for this fact. The salient 
features of the two localities, briefly sketched, are these; In the vicinity of 
Ithaca, there is a long, deep and narrow valley, having somewhat rolling, glen- 
cut sides. In it lies Cayuga lake, deep and weedless, stretching, like a broad 
river, to the northvvard. Its east and west banks are abrupt and rocky and cut 
at intervals by deep, wooded glens. A small grass swamp, bearing a few trees, 
at the south end of the lake, and running up into the city is about the only low 
laud in the vicinity. Formerly a mixed deciduous and evergreen forest covered 
the hills. Now, mere remnants stand near together upon small, close-packed 
farms on both sides of the valley. The houses are numerous, the orchards large, 
