PARASITICAL HABITS IN CUCULIDEZ—BARRETT. 489 
Plata ” (with whom I am in correspondence), are only partially para- 
sitical, being apparently still at the halfway house between virtue 
and vice. The cowbirds live together promiscuously, in flocks com- 
posed of many individuals of both sexes, and either build a nest for 
themselves or forcibly seize upon a suitable one belonging to some 
unfortunate member of another family of birds. In the event of 
there being either eggs or young in the appropriated nest the feathered 
robbers proceed to cast them out—a first trace of the ejecting in- 
stinct—before laying their own eggs therein. Strangely enough, 
cowbirds will sometimes construct a loose, untidy nest for them- 
selves on top of a stolen one, without making use of the latter for 
purposes of nidification. One species of Molothrus has the parasit- 
ical habit much more strongly developed than other members of the 
genus, as it almost invariably lays its eggs in the nests of other birds; 
but sometimes several individuals will club together and attempt the 
construction of a large, shapeless nest, which, however, is never com- 
pleted or made use of. These strange birds frequently lay as many 
as twenty eggs in a single nest, and they also possess the remarkable 
habit of piercing holes with their bills either in their own eggs or in 
those of other birds. Another curious fact relating to cowbirds is 
that one species (J/. rufaxillaris) is actually parasitic upon another 
member of the same genus (J/. badius), which builds its own nest. 
Additional proof of the gradual development of parasitism among 
the Cuculide is found in the fact that an American cuckoo (Coccyzus 
americanus), Which, as a general rule, builds a nest and rears its own 
offspring, has yet been known to depart from its normal habit in this 
respect and leave its pale green egg in an alien nest. The hawk 
ecuckoos (Hierococcyx) of southern India, which exactly resemble 
both in color and flight the sparrow hawks of that region, furnish 
still another instance. Of the six known species of Hierococcyx one 
only is said to build a nest, the remaining five being parasitic on the 
babbling thrushes. In the great spotted cuckoo (Coccystis glan- 
darius), ranging through southwestern Europe, Asia Minor, and 
Africa, we can see the instinct to shirk parental cares yet more 
highly developed. These birds are truly parasitical, inasmuch as they 
foist their eggs on certain species of crows and magpies whose eggs 
bear a marked resemblance in color to their own. In this case, how- 
ever, several cuckoo’s eggs are found in the same nest, and when 
these are hatched out it is stated that the intruders live in perfect 
harmony with such of their foster-brethren as have survived, and 
make no attempt to eject them. Occasionally the female spotted 
cuckoo, before laying in the chosen nest, breaks the eggs of the right- 
ful owner in order to make more room for her own. Thus we find 
the parsitical habit and instinct to eject fellow-nestlings being mani- 
