ECONOMIC RELATIONS OF OUR BIRDS. 
4G1 
birds of prey wliose residence is in latitudes south of our own, for there both 
our summer residents and birds of passage may be destroyed by them. 
(5) Do birds of ijrey perform a necessary ivork by holding in checJc certain 
birds and noxious animals ? “ Hawks and the larger Owls should be extermi¬ 
nated ” is the verdict of many, and yet we are far from liaving that knowledge 
of their relations to our needs which will justify the execution of such a ver¬ 
dict. We need a greater abundance of insectivorous birds than we liave at 
present, but it has not been demonstrated that a wliolesale destruction of all 
our birds of prey will not withdraw such a restraint from our vegetable-feeding 
species as to cause them all to become nuisances by their excessive abundance. 
Nearly all of them feed upon seeds or insects, at their pleasure. There are but 
few of them which are not known to feed to some extent upon grains and use¬ 
ful seeds. These facts appear to indicate that no bird is so likely to become 
excessively abundant in agricultural districts as they. It would appear that, so 
far as they are capable cf doing the work of insectivorous birds, they might 
even become injurious by simply crowding them out. Until these questions 
are securely settled, we must retain most of our birds of prey. We may exper¬ 
iment with them by reducing their abundance for a period, and carefully noting 
the effect which it has upon the abundance of other birds and upon that of 
noxious mammals. Since a bird once extirpated can never be reclaimed, no 
matter how much its services may be needed, the most guarded action in this 
direction can alone be justifiable. 
(6) Parasitism among birds. Birds which possess the habit of imposing their 
duties of incubation upon other species are to be ranked with Hawks and Owls, 
so far as their infiuence in regulating the abundance of birds is conceined. Out 
of nine Pewees’ nests, which were visited in the spring of 1878, at Ithaca, N. Y., 
by’my friend F. H. Severance and myself, two contained a single Cowbird each, 
and two contained Cowbirds’ eggs. Mr. C. N. Pennock informs me that three 
out of five Pewees’ nests visited by him contained one or two Cowbirds’ eggs 
each. These facts indicate that seven out of fourteen families of Pewees would, 
if their nests had not been disturbed, have hai their own broods destroyed, and 
that instead of some 28 or 35 Pewees which they would have reared, only seven 
Cowbirds could have taken their places as insect destroyers. Such is the infiu¬ 
ence which this bird exerts over the abundance of the Pewee. 
A long list of other birds, similarly affected, has been determined, and the 
majority of the members are among the most exclusively insectivorous birds we 
have. 
(7) The scientific, educational and cesthetic value of birds. This, though 
mentioned last, is not the least consideration which should challenge the thought¬ 
ful and infiuential whenever a bird is proposed for extermination. Prof. Alfred 
Newton, in an article on the extermination of species (Am. Jour, of Sci., Dec., 
1876), has pointed out, in a general way, the dangerous tendencies in this direc¬ 
tion, and justly calls upon men of science to take a stand in behalf of posterity. 
In view of the many importaTit unsolved problems relating to life and its phe¬ 
nomena, the first factors of whose solution we already have, it is certain that 
the living species are too few to supply the much needed data, and that stuffed 
skins and dry bones can, in no adequate way, answer such questions as should 
be put to animated tissues. These, in my judgment, are sufficient reasons for 
not now recommending the absolute extirpation of any bird. 
In the light of educational needs, the case of the detrimental bird appears 
still stronger. It is certain that, as our methods of instruction improve, the 
