Page:Territory in Bird Life by Henry Eliot Howard (London, John Murray edition).djvu/38

16 inhabiting a certain piece of marsh are divided into two classes, those which are pugnacious and intolerant of the approach of strangers, and those which welcome their presence. The nests of the former will be built in isolation, those of the latter in close proximity. In due course eggs will be laid and incubation performed, and thus far all alike will probably be successful. Here, however, a critical point is reached. If the young are to be freed from the risk of exposure, the parents must find the necessary supply of food rapidly. But manifestly all will not be in a like satisfactory position to accomplish this, for whereas the isolated pairs will have free access to all the food in the immediate vicinity of the nest, those which have built in proximity to one another, meeting competition in every direction, will be compelled to roam farther afield and waste much valuable time by doing so; and under conditions which can well be imagined, even this slight loss of time will be sufficient to impede the growth of the delicate offspring, or to lead perhaps to still greater disaster. If any one doubts this, let him first examine one of the fragile offspring; let him then study the conditions under which it is reared, observing the proportion of time it passes in sleep and the anxiety of the parent bird to brood; and finally let him picture to himself its plight in a wet season if, in order to collect the necessary food, the parents were obliged to absent themselves for periods of long duration.