female not rising to the height of such a definition. To how great an extent this law prevails I have not the knowledge to say, but it is not universal. The female canary, robin, lark, and bullfinch all sing, especially when widowed, though their song is not equal to that of the male, whilst in the red oven-bird of Argentina both sexes frequently join one another for the express purpose of singing a duet. Surely in this last case, especially, if it be assumed that the song of the male is uttered with the purpose of pleasing the female, or has that effect, the converse ought also to be assumed: and if so, why should not the hens, as well as the cocks, be sometimes chosen for their song?
But all nuptial notes of birds are equally song, in the sense that they are uttered under the impulse of sexual passion, and many of these are the same in both the sexes. Here, again, there is a danger of assuming, without sufficient evidence, that the characteristic courting or love-note is uttered only by the male. A mistake of this kind has been made in the case of the nightjar—both sexes of which I have heard "churr" together on the nest—and no doubt in many other instances, including, very possibly, the cuckoo. In a vast number of cases, however, the cries of the two sexes during the love-season are known to be the same. They may not always, when this is the case, be either very wonderful or very beautiful, but to suppose that the nuptial actions and notes of male birds are intended to attract and charm
