NIDIFICATION 633 
species brooks not the society of aught but its mate. Birds there 
are of eminently social predilections. In Europe, excepting Sea- 
fowls—whose congregations are universal and known to all—we 
have perhaps but the Herons, the FIELDFARE, and the Rook, which 
habitually flock during the breeding-season ; but in other parts of 
the world many birds unite in company at that time, and in none 
possibly is this habit so strongly developed as in the ANIS of the 
Neotropical Region, the Republican Swallow of North America, 
and the Sociable Grosbeak (WEAVER-BIRD) of South Africa, which 
last joins nest to nest until the tree is said to break down under 
the accumulated weight of the common edifice.! 
In the strongest contrast to these amiable qualities is the para- 
sitic nature of the Cuckows of the Old World and the Cow-BirRDs 
of the New, but this peculiarity of theirs has been already dwelt 
upon. Enough to say here that the egg of the parasite is introduced 
into the nest of the dupe,.and after the necessary incubation by the 
fond fool of a foster-mother the interloper successfully counterfeits 
the heirs, who perish miserably, victims of his superior strength. 
The whole process has been often watched, but the reflective 
naturalist will pause to ask how such a state of things came about, 
and there is not much to satisfy his enquiry. Certain it is that 
some birds whether by mistake or stupidity do not unfrequently 
lay their eggs in the nests of others. It is within the knowledge 
of many that Pheasants’ eggs and Partridges’ eggs are often laid 
in the same nest, and it is within the knowledge of the writer that 
Gulls’ eggs have been found in the nests of E1prer-Ducks, and vice 
versa ; that a REDSTART and a Pied FLYCATCHER, or the latter and 
a TITMOUSE, will lay their eggs in the same convenient hole—the 
forest being rather deficient in such accommodation; that an OWL 
and a GOLDEN-EYE will resort to the same nest-box, set up by a 
scheming woodsman for his own advantage ; and that the STARLING, 
which constantly dispossesses the Green Woodpecker, sometimes 
discovers that the rightful heir of the domicile has to be brought 
up by the intruding tenant. In all such cases it is not possible to 
say which species is so constituted as to obtain the mastery ; but 
just as it is conceivable that in the course of ages that which was 
1 There are not many works on nidification, for ‘‘Caliology” or the study of 
nests has hardly been deemed a distinct branch of ornithological study. A good 
deal of instructive matter (not altogether free from error) will be found in Rennie’s 
Architecture of Birds (London: 1831), and there is Mr. Wallace’s most interest- 
ing dissertation, ‘‘ A Theory of Birds’ Nests,” originally published in the Journal 
of Travel and Natural History (1868, p. 73), and reprinted in his Contributions 
to the Theory of Natural Selection (London: 1870). Andrew Murray’s and the 
Duke of Argyll’s remarks on this essay are contained in the same volume of the 
Journal named (pp. 137 and 276). The late Mr. J. G. Wood’s Homes without 
Hands, perhaps the best of his books, contains a popular account of many Birds’ 
nests, but is devoid of scientific treatment and disfigured by some glaring errors. 
