BREEDING HABITS OF WEAVERBIRDS—FRIEDMANN 313 
devoid of direct reproductive function, coupled with apparently 
monagamous coition-inviting display by mated females. Nest build- 
ing may vary from solitary to highly communal, and to none at all, 
and even to parasitism, from slovenly put together masses of material 
to amazingly fine and intricate weaving, or huge, communal super- 
structures, or may be reduced to merely relining a disused nest of 
another species or to lining a hole in a tree. Nest construction may 
be done entirely by the male, by both sexes, or largely by the female, 
or may be omitted entirely. Sexual relations vary from solitary 
monogamy or social monogamy to polygamy, polyandry, and to ap- 
parent promiscuity. Incubation in some species, or groups of species, 
is performed solely by the hens, while in others the cocks share the 
task with their mates, or, in the case of still others, neither sex takes 
any care of the eggs, but are parasitic. 'The members of the subfam- 
ilies Ploceinae and Viduinae do not come into breeding condition or 
acquire adult breeding plumage until they are 2 years old; the mem- 
bers of the other groups breed when 1 year old; this in itself is a pro- 
found difference. In some forms of the Viduinae and Ploceinae it 
permits a type of breeding-season gregariousness, although only a 
single adult male and female are usually involved in each little flock. 
Few, if any, families of birds offer such a bewildering array of 
variations of the parts of the annual cycle, and I cannot help but 
wonder if some of these variations may not have been due originally 
to the extremes to which, in previously established variations, some of 
the stages had been carried. At least the situations created by some 
of these extreme developments seem to have been propitious for 
further and even quite contrary subsequent changes. 
Paradoxical as it sounds, it is possible that the excessive develop- 
ment of the nest-building habit may actually have been a contributing 
factor in the origin of the complete absence of nest building and egg 
care that we know as brood parasitism. In cases of extreme indul- 
gence in nest construction such as we find in the social weaverbird 
(Philetairus socius) and some of its relatives (Plocepasser etc.), the 
huge bulky structures are added to, chiefly by the males, all through 
the nonbreeding season. By the time the birds are ready to make 
their own individual nest tunnels in the already existing superstruc- 
ture they are not acting very differently from birds that make use of 
old nests of other species which they then repair. In the case of the 
numerous species of typical weavers (Ploceinae) in which the not yet 
breeding males construct many nests, the subsequently mated females 
are again in a not dissimilar position of taking over nests which they 
themselves have not built, and relining them and breeding in them. It 
seems that Ali (1931) must have had some such thought in mind 
when he noted that Baya weavers occasionally laid eggs in disused 
