126 THE BIRDS OF HELIGOLAND 



as nineteen instances are recorded as having occurred on English 

 soil. Further, in regard to this group of birds, we must not forget 

 that they live almost exclusively on the opposite shores of the 

 ocean, and are already well experienced in flying across wide 

 expanses of water, having no doubt, in the course of their life, fre- 

 quently crossed seas and inland lakes, of which the opposite banks 

 would not have been visible at the commencement of their journey, 

 nor would the}^ have any previous knowledge of the distance to be 

 traversed. Such birds, then, when they set out on their journey 

 over the Atlantic, are not conscious of the task they are undertak- 

 ing : in fact they have no inherent notion of the duration of time, 

 all that is required being that their strength should hold out until 

 the whole distance is accomplished. Hitherto we have had nothing 

 which could have assisted us in estimating the extent of their 

 capacity in this direction, though there can be no doubt that so far 

 as powers of locomotion go, they surpass to an immeasurable degree 

 every other division of the animal kingdom. 



After what has been said in the preceding, we are confronted 

 by the question as to what may be the causes of these surprising 

 migration flights ; for although, generally speaking, they must be 

 regarded as exceptional phenomena, they occur far too frequently 

 to allow us to regard them as due to accidental straying on the 

 part of the birds from their normal routes of migration, or to their 

 having been beaten out of their regular course b}' storms. Moreover, 

 the number of species which resort to these exceptional migrations 

 is, comparatively .speaking, so small, and the movements themselves 

 are repeated with such frequency, that we are forced in their case to 

 assume the operation of causes which do not aftect other species, 

 even though these may be closely related to the former. We must 

 add to this the fact that the numerous instances above cited, as 

 well as other less frequent occurrences of shore-birds and waders, 

 have been observed almost exclusively during the autumn months. 

 Now, this circumstance leads one to suspect that we are here deal- 

 ing with a phenomenon analogous to that witnessed in the case of 

 species from the east of Asia, with the difference that in the present 

 case the deviation from the normal southern course of the migra- 

 tion is a fixed one to the east instead of to the west, and that here 

 again, while some species — such as, for instance, the Americiui 

 Bittern before named, various species of Tringa and the like — are in 

 a high degree subject to a tendency for turning ott' in this manner 

 from their normal migration track, many others exhibit no inclina- 

 tion whatever of this kind. Of the latter kind of birds, the Plovers 

 from the opposite coast of the Atlantic furnish a good illustration, 

 only one species, Characlrius vircjinicxis — a bird which every 

 autumn travels in countless multitudes across the sea from Labrador 



