where other birds are not in the habit of coming, I have known many cases, in camps containing from eighty to one hundred birds of both sexes, where the pair have kept the nest exclusively. Such a nest, unless destroyed by rains or wild animals, is almost certain to yield a large proportion of chicks. This cannot, perhaps, be said of a nest under any other conditions. If, during the laying of the eggs, or after the pair have begun to sit, other hens lay in the nest or sit on it, the yield of chicks will not be so great; there will never, as far as my experience goes, be a good yield; often there are no chicks at all. The pair frequently abandon the nest. A good yield of chicks, in proportion to the eggs laid, is seldom obtained from any nest in which more than one hen lays or broods; with two hens, a good yield may be got in proportion to the eggs actually sat upon; when there are more than two hens, a few chicks may hatch out, but in the great majority of cases there will be none. The chance of obtaining any yield at all lessens as the number of hens increases; with four or more hens it is almost safe to say that chicks never result.
Yet it is undeniable that in a camp where many Ostriches run, nests are generally shared by several hens, usually by more than two. I have known six or eight to share one nest, and have found a nest with one hundred and fifty eggs in and about it, many with from fifty to seventy; but it is very exceptional—in fact, almost unknown—for such nests to yield chicks. If it were natural for several hens to share one nest, chicks should result.
All the hens of one nest keep to that nest, each laying generally about a sitting, and then beginning to brood. If they cannot lay in the nest because it is occupied, they will not often go to another nest, but will deposit their eggs just outside their own. Each nest is owned by one cock; but I do not know, when there are several hens laying in one nest, whether they are all fertilised by the cock of that nest.
Why several Hens often Share one Nest.
Now, how is it, if the Ostrich is not polygamous, that several hens often share the same nest?
The following considerations may not quite solve the question, but serve, I think, to help towards its solution.
