VARYING FECUNDITY IN BIRDS.
By Basil Davies.
Mr. Warde Fowler, in one of his bird stories, describes the uneasiness of a youthful hen Wagtail when she began to ponder on the question, "Why do we wag our tails?"—the moral being, I suppose, that facts come before reasons for facts, and ought to suffice for most of us. Checked somewhat by this allegory, my ideas on the above subject received a fresh impetus when, in 'Summer Studies of Birds and Books,' I read that Mr. Warde Fowler actually felt it his duty to ask and to attempt to answer that very same question which used to trouble his little hen Wagtail. I have no apology of duty to offer for my poor attempts at explanation: I can only say that the subject is one to which very little attention has been given, and that it is one in which a really skilful ornithologist could probably make most successful researches.
The ordinary birdsnesting naturalist regards an abnormal clutch, whether large or small, only with a view of its suitability for his collection. He robs a Nightingale of five eggs and a Partridge of fifteen without attempting to explain why the offspring of the one species is numerically so superior. Some years ago, reviewing my season's "take" of eggs, I felt myself somewhat of a monster when I imagined the table on which my cases lay peopled with those birds whose embryos I had removed from every shell—six Nightingales, a dozen Bullfinches, and so on—though I never took more than one egg from a nest. Consequently, in abandoning collection, I sought for a new interest in eggs to take its place; and this chapter is an endeavour to explain the interest of a different sort that I now take in the nests I find.
There are certain general principles which it is well to keep in mind in this particular branch of bird-study. Such is the rule, that birds do not merely breed so many times a year in the course of nature, but that they feel it their duty not only to
