Page:The British Warblers A History with Problems of Their Lives - 4 of 9.djvu/18

 on the coast of Uleaborg, it is common; this is especially the case on the Island of Carlo, in the vicinity of Willmanstrand, and on the shores of Lake Ladoga. It also occurs in the neighbourhood of Lake Onega, in the Province of Olonetz, and eastward of this visits the Provinces of Vologda, Viatka, and Perm. In Poland and the Baltic Provinces the bird is very common, and in fact throughout Central and Southern Russia, and in the valley of the Volga it is generally distributed. Further east it becomes less plentiful, though occurring in the provinces of Orenburg, the Kirghiz Steppes, and in Astrakhan, and to some extent breeding in the Caucasus.

In Asia Minor it occurs in summer.

There are records of its occurrence in Cyprus, but Crete and Malta are visited on migration only, and it appears to breed in parts of Algeria, Tripoli, and Tunis.

In winter it visits North-east, Central, and West Africa, as far south as Damaraland, and also Arabia and Madeira.

There is little variation in the dates upon which the first male reaches these islands, or at any rate the Midland Counties, and under ordinary conditions they may be expected between April 19th and 25th, though, if exceptional climatic conditions prevail, the migration may be checked. Such was the case in the year 1908, when a snowstorm of considerable severity occurred about April 25th, with the result that the males did not begin to arrive until April 30th.

In the numbers in which they visit us from year to year they vary considerably, and this variation is in some measure due to a local and temporary influx into certain districts, for it often happens that whereas they may be plentiful in one district, in another one adjoining they may be unusually scarce. It cannot, however, be doubted that there are in addition influences at work outside the British Islands—