NATURAL HISTORY SOCIETY OP GLASGOW. 279 



the prevalence in October of severe and continued gales from the 

 north-west, coupled with the occurrence, as noted by Mr. Stevenson, 

 of large shoals of herrings and sprats at that period on the east 

 coast. 



Their line of flight seems to indicate that migration takes place 

 across the narrow neck of land between the Friths of Forth and 

 Clyde, and, indeed, this is borne out by observations, at various 

 times, of other species. The central counties of Scotland appear 

 to form no barrier to the annual autumn migration of birds, which, 

 striking our east coast, at localities north of the Frith of Forth, 

 frequently find their way across to the Frith of Clyde. 



It may be remarked as a curious fact, that the central tail 

 feathers, which form one of the most characteristic features of the 

 species, were, in the case of nearly all the specimens obtained in 

 Scotland, much abraded and worn — a circumstance which seems 

 difficult of explanation. This seems to have been previously 

 observed by French naturalists, one of whom, M. Hardy, of Dieppe, 

 affirms that the Pomatorhine Skua assumes in winter a plumage 

 more or less resembling that of the young, that they then lose the 

 central rectrices, which, if the moult is delayed, become a source 

 of irritation to the bird, and in that case it breaks them over to 

 obtain relief. Messrs. Degland and Gerbe, on the other hand, 

 attribute the frequent occurrence of the feathers in a broken state, 

 at this season, to abrasion by the ice before leaving their breeding 

 haunts, or to the action of the gales, which drive the birds on the 

 coast. Such great flights as the one under notice have, according 

 to the last-mentioned authors, occasionally occurred on the northern 

 coasts of France — notably in the month of October, 1834, when a 

 great storm prevailed for several days in succession. 



Before concluding this brief and imperfect record, one more fact 

 in connection with the recent Skua flight may be mentioned, viz., 

 the detection, for the first time, of several cases of melanism 

 among the specimens, which were obtained, both in England and 

 Scotland, two of which in the latter were shot at North Berwick 

 on 31st October. This form, although known to occur in the 

 allied species S. crejridatus, had not been previously well authenti- 

 cated in that now under review. A notice of this, from the pen 

 of Mr. Howard Saunders, appeared in the Field of January 1 7th, 

 1880.* 



* Reprinted in the Zooloyist, 1880, pp. 90-97. 



