Another point remains to be noticed, and that is the greater frequency and fulness in displays of all kinds, including song, during the love season. And here Dr. Wallace's colour and ornament theory helps us to an explanation. At the season of courtship, when the conditions of life are most favourable vitality is at its maximum, and naturally it is then that the proficiency in all kinds of dancing-antics, aerial and terrestrial, appears greatest, and that melody attains its highest perfection. This applies chiefly to birds, but even among birds there are exceptions, as we have seen in the case of the field-finch, Sycalis luteola. The love-excitement is doubtless pleasurable to them, and it takes the form in which keenly pleasurable emotions are habitually expressed, although not infrequently with variations due to the greater intensity of the feeling. In some migrants the males arrive before the females, and no sooner have they recovered from the effects of their journey than they burst out into rapturous singing; these are not love-strains, since the females have not yet arrived, and pairing-time is perhaps a mouth distant; their singing merely expresses their overflowing gladness. The forest at that season is vocal, not only with the fine melody of the true songsters, but with hoarse cawings, piercing cries, shrill duets, noisy choruses, drummings, boomings, trills, wood-tappings--every sound with which different species express the glad impulse; and birds like the parrot that only exert their powerful voices in screamings--because "they can do no other"--then scream their loudest. When courtship begins it has in many cases the effect of increasing the beauty of the performance, giving added sweetness, verve, and brilliance to the song, and freedom and grace to the gestures and motions. But, as I have said, there are exceptions. Thus, some birds that are good melodists at other times sing in a feeble, disjointed manner during courtship. In Patagonia I found that several of the birds with good voices--one a mocking bird--were, like the robin at home, autumn and winter songsters. The argument has been stated very binefly: but little would be gained by the mere multiplication of instances, since, however many, they would bo selected instances--from a single district, it is true, while those in the _Descent of Man_ were brought together from an immeasurably wider field; but the principle is the same in both cases, and to what I have written it may be objected that, if, instead of twenty-five, I had given a hundred cases, taking them as they came, they might have shown a larger proportion of instances like that of the cow-bird, in which the male has a set performance practised only during the love-season and in the presence of the female.