548 MIGRATION 



term of years ; but, though we may safely predict that if they 

 appear at all they will do so at a certain season, it is impossible to 

 make a forecast as to the year in which an example will arrive, or 

 whether in one year some half-dozen may or may not occur. The 

 matter thus becomes a matter of averages, and like all such is open 

 to the influence of many perturbants, not that such may not well 

 be subject to some law of which we are ignorant. Beside this, the 

 average is hard to strike, depending as it must on the existence of 

 favourably-placed and watchful observers. Moreover if we consider 

 that the number of competent observers, though possibly as great 

 in England as anywhere, has been at all times small, it is not sur- 

 prising that little has been effected towards the compassing of any 

 definite notion on this head. At present we can but attribute the 

 appearance of some foreign stragglers on our shores, and no doubt 

 the same may be said of other countries, to the influence of storms 

 which have driven the wanderers from their course, and though 

 other more remote causes may possibly be assigned, there seems to 

 be none but this on which we can safely rely. Consequentl}^ until 

 the periodicity of storms is brought within our knowledge we must 

 be content to abide in our ignorance of the laws which govern the 

 appearance of the strangers. Still confining our remarks to the 

 British Islands, the effect of these laws is in some degree constant. 

 Singular as it may appear, the greatest number of North-American 

 Birds — and especially of the Limicolse, which are recorded as having 

 occiirred in this country have been met with in the eastern part of 

 England or Scotland. There are two ways of accounting for this 

 fact, the first of which is the comparative scarcity of observers in 

 Ireland and on its western coast especially, and this is by no means 

 to be overlooked ; but it may be remarked that in no part of the 

 United Kingdom is the profession of the gunner more enthusiastically 

 followed than in the sister-island, and the men who pursue that 

 vocation are all alive to the mercantile value of any strange bird 

 which may fall in their Avay. Of course they have no means of 

 knowing what it is, yet as their spoils are sent for sale to the 

 nearest market, it cannot but happen that if many examples of 

 North-American species were procured by them, some proportion 

 of these would find their way to the notice of the amateur naturalist 

 and by him be recorded in the public prints.^ Noav, as compared 

 with Great Britain, this so rarely occurs in Ireland that it is by no 

 means unfair to draw the inference that Transatlantic Birds are 

 there far less frequently met with. The second mode of account- 



^ It seems also not unlikely tliat the very scarcity of rare birds in Ireland is 

 one reason why there are so few ornithologists in that country, for here it is not 

 uncommon for a man to have his attention first called to zoology by meeting 

 with .some strange animal — be it beast, bird, beetle, or butterfly, and for such a 

 man afterwards to become no mean field-naturalist. 



J 



