culties of the males there similarly situated; and even allowing that they are at length successful in establishing themselves, what are their prospects of securing mates? Since the earlier females will not extend their wanderings farther than is absolutely necessary, but will pair whenever the opportunity for doing so arises, it is to the later females, forced onwards by competition, that the late males must look for mates; so that when at length pairing does take place, much valuable time will have been lost.
The disadvantages which the late arrivals have to face are therefore great, and it is probable that the percentage which attain to reproduction will on the average be somewhat lower than the percentage in the case of the earlier arrivals. The district in which my observations have been made lies well within the limits of the breeding range of most of our common species, and it is not surprising that I should have met with little evidence of failure to breed as a result of failure to secure territory. Some interesting information was supplied to me, however, by the late Robert Service. He found, in certain seasons in Dumfriesshire, flocks of from ten to fifty unmated Sedge-Warblers, which, from the time of their arrival in May until the middle of July, haunted reed-filled spaces along stagnant streams. These flocks appeared to him to be composed of loosely-attached individuals of a migrant flock that had failed to find things
