fresh localities. The fact that some species, such as the Corncrake, appear to be dying out in certain districts is evidence that there is not a general redistribution over the country each year. In general, as is easily seen in the case of the Wheatear and Yellow Wagtail, the males arrive first, as if to take possession of the old home or seek a new one before they are followed a few days later by their mates. If we compare the migration, say of the Willow Wren, to a wave breaking on our shores, its crest will represent the main arrival, while a series of succeeding ripples will stand for the smaller parties which continue to come in for several days. When the wave is an unusually strong one, it seems to carry individuals beyond the ordinary range of the species. Thus it is only in certain seasons that the Lesser Whitethroat reaches Western Wales. The laggards, constituting the final ripples of the wave, are probably birds which are going much further north to nest. Thus long after our resident Wheatears have settled down to breed, in fact all through April and May, other wheatears may be seen on passage. These we imagine to be on their way to Iceland or Greenland, where the climate renders it impossible for them to nest until a comparatively late date.
In an ordinary April we may expect to note some twenty arrivals, the bulk of them naturally falling within the last ten days of the month. It is the
