Page:The British Warblers A History with Problems of Their Lives - 1 of 9.djvu/21

 The males, when they first arrive, select a certain spot of not many square yards in extent, with a tall bush or willow conveniently situated; and, moreover, they not only choose a tree but some particular branch on that tree, and this, until the young are hatched, forms their headquarters. Before the female arrives, and also, but not as much, when paired, they sit on this particular branch and pour out their song, frequently accompanying it with a pretty ærial flight, rising almost perpendicularly for a short distance in the air, turning very quickly and returning, with wings and tail outspread, to the branch. After a short rest they either start their song afresh, begin to preen their feathers, or go in search of food, wandering over the branches of the various willows, examining the under parts of the leaves for flies of the genus Chironomus, and the twigs for aphides, working lower and lower down through the branches and thick herbage till they reach the ground, and here for a time they make their way in search of aquatic insects and small spiders, only shortly to return to their favourite branch, singing as they fly. Thus they while away the days till the females arrive. The ground immediately surrounding the tree they have chosen as their headquarters they look upon as particularly their own, and when two or three have chosen positions close to one another, there they will be found to search for their food in certain well-defined directions, being most careful not to poach on one another's preserves, and consequently most jealous of any intrusion on the part of their neighbours, and not, indeed, only of their neighbours, but also—and this I have seen so frequently as to place it beyond the bounds of chance—of any other warbler, chasing them determinedly away, while frequently—I have seen them pursuing Thrushes and Hedge-Sparrows—ignoring the presence of other species so far as to allow them to nest in their favourite tree. Such powers of apparent discrimination seem very wonderful, yet we must not forget our total ignorance of all things pertaining to the sub-conscious state of animal life, and