On capacity in nest-construction.



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CAPACITY IN NEST-CONSTRUCTION.


By Dr. Arthur G. Butler.


The fact that different groups of birds exhibit enormous

variations of ability in their artistic efforts must be patent to all who

•compare the perfect work of a Long-tailed Tit with that of a Wood-

pigeon ; but it seems to me that in cases where one sex only acts as

architect there is no evidence to prove that the opposite sex is not

equally gifted with the capability of nest-construction.


Then again, in the case of birds which do not build, but lay

their eggs in the nests of other birds, it is more than probable that

other reasons than incapacity are the cause of this behaviour.

Although many of the Cuckoos are parasitical in their habits, the

Ground-cuckoos and other groups build nests and rear their own

young ; therefore it has been suggested that, being polyandrous

birds, the hens of our Cuckoo “ are obliged to wander in search of

birds of the opposite sex ” (Seebohm, ‘ British Birds,’ vol. ii, p. 382).

The fact that I have seen a hen Cuckoo pursued by three cocks does not

seem to support this conclusion, but seems rather to argue in favour

of the view that the hen Cuckoo is so constantly pestered by the

attentions of numerous suitors that she has no time to spare for

nest-construction.


This polyandry in the Cuckoo does not appear to interfere

with the abundance of the species, since, as Darwin argues (‘ Descent

of Man,’ 2nd ed., p. 904), where the number of males greatly exceeds

that of females it is evident that none of the latter will lack

husbands. In the case of insects we may notice that where the

males are far more numerous than the females (as, for instance, in the

case of our common Vapourer-moth (Orgyia a?itiqua) the species is

very abundant.


As we are all aware, in many groups of birds only one sex

busies itself in nidification; while the other sex often calmly looks

on, or at most pays only casual visits of inspection during the

progress of the work, which it sometimes even hinders by officious

meddling. In other groups both sexes are engaged upon part or the

whole of the building.


Now, in cases where only one sex does the work, we must not



