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MR. J. S. HUXLEY ON THE 
Share of the sexes in nest-building, 
The only data are based on the actions of a single pair—that 
observed by Selous in 1900; we must not, therefore, generalize 
too far. However, certain things emerge clearly. Both sexes 
work vigorously at the nest. During nest-building, the cock 
builds a platform by and for himself not far from the nest, In 
this particular pair the cock seemed slightly more active in nest- 
building, though the hen was more skilful. This may be, and 
probably is, merely an individual trait. As far as the building 
of the true nest goes, both sexes seem to be at least as similar as 
they are, for example, in appearance and in courtship habits. 
‘The mysterious platforms of the cock remain as one of the few 
truly secondary sexual characters of the species. 
Psychology. 
It seems probable that the same sort of psychological mechanism 
holds here as in courtship. Fetching weeds from the bottom and 
piling them in a heap is an instinctive act affording pleasure or 
relief. Although it is much easier to Imagine a bird deriving 
pleasure from solitary nest-building than from solitary courtship 
action, yet here, too, it seems as if the cock and hen are mutually 
stimulated to activity. This is, at all events, an eminently useful 
trait, for it ensures that the nest shall be quickly built, that 
the pair shall keep together, that they shall build one nest at 
a time (instead of two, perhaps widely separated ones), and so 
forth. 
That it is pleasurable may be further inferred from the fact 
that when the fever is upon them the birds may build two large 
nests in two successive days (Selous, loc. cit). This may seem 
wasteful, but here, as in so much else, Nature indulges in a 
considerable reserve—better too much than too little. This is 
the case with reserves of food, our own appetites, the number of 
times which most animals pair, the number of unpaired males 
in polygamous species and in Bees, etc., ete. Here, perhaps, the 
reserve is indirect rather than direct; it may not even be any 
advantage to have built two nests instead of one, but it may well 
be an advantage to have such a strong nest-building instinct that 
two or more nests happen to result, instead of one. 
Finally, again, as in the courtship, association plays its part. 
What has once been done with pleasure, is done again easily as a 
habit. So when a bird is near the finished nest. and especially 
when the birds are there together, weeds are often added, but 
almost always in a more or less perfunctory way. 
Why, after one bird has unsuccessfully invited its mate to pair 
on the platform, it should often dive and bring weed to the plat- 
form, I donot fully see. We can only say that diving and weed 
