BRITISH WARBLERS
generally some days after the first male; but the migration of the sexes overlaps, males continuing to arrive with the females. There is as great a variation in the plumage of the females as in that of the males, the immature birds being easily distinguished by their dull appearance and by a conspicuous absence of that intensity of colouring and development of feather which are such prominent beauties of a more fully mature bird.
The duration of the courtship depends. I believe, solely upon the female; for it sometimes happens that on her arrival she is not in a condition to breed, and in such a case she passes unnoticed amongst the unpaired males, her presence having no exciting influence upon them; she is thus allowed to seek her food and pursue her way unmolested. But this is by no means a usual occurrence; her presence is generally a signal for an intense outburst of sexual passion. In no other way, it seems to me, can we account for the variation in the duration of the courtship. In one year, for instance, in which the males were very late, a solitary female arrived first. The first male that arrived paired immediately with this female; there was little excitement or courtship, the nest was rapidly built, and the young were hatched within a month from the date of his arrival. But, on the other hand, it is by no means uncommon to see pairs actively engaged in their courtship for many mornings in succession.
By the term courtship I refer always to the period between the time in which a female settles in the territory of a given male and the time when the first egg is laid. This period is always one of excitement to the male; an excitement which, varying in intensity with the nervous organisation of the species, vanishes temporarily the moment the sexual passion is relieved, but reappears, although in a lesser degree, before each act of coition.
There seems indeed to be some connection between the
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