BRITISH WAttBLEliS 



about the same time, Professor Goeldi that they reach Switzer- 

 land from the middle of April to the middle of May, Count 

 Salvadori that they arrive in Northern Italy during the latter 

 half of April and the beginning of May, and M. Buturlin 

 that Poland is reached towards the end of April, Southern 

 Eussia from the middle of April to the middle of May, 

 the Baltic Provinces during the first half of May, Central 

 Eussia about the middle of May, and the Province of Kasan 

 towards the end of that month. Here, then, we have a 

 peculiarly contradictory set of facts. Let us see what the 

 variation amounts to. In England, the normal period of 

 arrival is the end of May, or the commencement of. June, in 

 Texel the early part of June, but in Germany and Hungary 

 the beginning of May, one month earlier, that is to say, than 

 the normal period in Western Europe ; whilst in Switzerland 

 it is the middle of April and in the South of France the 

 commencement of that month, almost two months earlier 

 • than the average date of arrival in this country. Assuming 

 that all these dates are approximately correct, we have a 

 variation which is probably unsurpassed by any other migrant 

 — at least it is not approached by those with which I am more 

 especially familiar. Variation in the case of all migratory 

 species must and does occur up to a point. The more southern 

 parts of Europe are, as a rule, the first to witness the return 

 of these heralds of spring, and even the territories in the 

 southern counties of England are, on the average, appropriated 

 somewhat earlier than those in the north. But in all such 

 cases the difference in time may be more conveniently reckoned 

 in days than in weeks, still less in months. As an example, 

 we have the Eeed Warbler which arrives in Hungary about 

 April 20th, ten days or so before it may be expected in England, 

 and the Eeed Warbler, be it remembered, is closely related to 

 the Marsh Warbler, a fact which makes the variation in the 

 case of the latter species even more significant. There is 

 nothing to account for this extreme variation ; there is nothing, 

 so far as we can judge, in the reproductive instincts of the 



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