on capacity in nest-construction.



173



Ploccine Weavers the males also collect and build, until only the

cup to contain the eggs is lacking to complete the structure; then

the offices of the hen are requisitioned, and she, sitting inside upon the

transverse bar which divides the double opening of the uncompleted

nest and her husband on the outside at the back, they pass the

grasses backwards and forwards to each other, weaving them into a

firm receptacle.


Whether both sexes of the Hangnests collect the materials as

well as working together on the construction of the nest I do not

know, but from what we know of other sociable birds it seems

probable: it is certainly the case with the Waxbills, and I think

also with the Grassfinches and Mannikins.


It appears to me that the explanations for these varied

methods must differ in the case of each group ; thus the hens of

the typical Finches and perhaps of most of the small European

perching birds, are impelled to build because they feel the need for

a suitable cradle for their eggs; whereas the cock birds are not

conscious of any such need, though they may be so far interested as

to be willing to choose a site for the nest and prepare the where¬

withal to build it.


In the case of the more impetuous, amorous, and often poly¬

gamous Weavers, the males build as an inducement to the females

to start housekeeping, and frequently produce far more nests than

are required ; perhaps in order to give the future bride a choice of

residences. The habit of multiplying nests appears in this way to

have become so ingrained in their nature that a supply of building

material will start many Weavers nest-building when no hen birds

are present to make use of the structures ; consequently the nests

built by Ploccine Weavers, when unpaired are always imperfect, in

my experience, the assistance of the hen bird being required to

enable the cock to complete the cup.


I have seen it authoritatively asserted (so far as I remember,

in an article published in the ‘ Transactions ’ of the Linnean or

Zoological Society by an Indian Civil Servant*), that cock Weavers

are in the habit of purposely building these unfinished nests as



* I am afraid this is very vague; but it is many years since I saw the statement,

and, though my memory is good, it is far from perfect.



13



