.^, THE MIGRA TION OF BIRDS. 777 



Malta. Where a line of migration has been used from remote ages, 

 birds continue to follow the same by hereditary instinct, be it sea or 

 land. 



Within comparatively modern times some species of Western 

 Palaearctic birds are known to have extended their summer range 

 eastward, and likewise Eastern Palaearctic birds have spread west- 

 ward; yet notwithstanding the increased geographical area occupied 

 — notwithstanding the much greater distances to be Jtraversed — they 

 still continue to follow the old lines of migration which they have 

 been accustomed to from the remotest periods. 



Islands situated far from migratory routes, as a rule, become 

 isolated areas, and include in their special avifauna the greatest 

 number of endemic species. The reverse is the case when they are 

 situated within the range and influence of long-established routes. 

 As one instance of a sedentary and island species which does not 

 migrate, Mr. Dixon has inaptly chosen the so-called St. Kilda^wren. 

 This most unfortunate little bird was recently (1884) exalted into a 

 distinct species under the name of Troglodytes hirtensis, but without 

 sufficient cause ; and one result is that it has already been exterminated 

 by greedy collectors, who are able to offer the poor islander consider- 

 able reward for its capture. 



Mr. Dixon says "it is a rule almost without exception that the 

 wings of migratory birds are long and pointed " ; also " that migrants 

 decline to make any very extended flights across the sea, except the 

 most fleet-winged and robust." " Small terrestrial species of com- 

 paratively feeble flight choose, invariably, the easiest way across, 

 where choice is possible." The fact is, however, that many birds, 

 with wings suggestive of weak flight, or such as are not in the habit 

 of taking extended journeys on land, do succeed annually in the 

 autumn in crossing the North Sea in its widest part in a single flight. 

 Such are the jay, grey shrike, common wren, hedge-sparrow, red- 

 breast, great and blue titmice, water-rail and others. On the other 

 hand, some purely sedentary species possess long and pointed wings. 



Having lived near the East Coast of England nearly all our life, we 

 have in each autumn had unusual opportunities, for days in succession, 

 of watching immigration in actual operation, and to note that, under 

 the conditions of favourable weather, birds appear to be absolutely 

 unaffected by the sea passage; and even after a bad crossing — storms 

 or adverse winds or driving snow — a few hours' rest seems sufficient 

 to enable them to renew the journey. 



We cannot understand what Mr. Dixon intends when he speaks 

 of " migratory land-birds, many of them frail in form and constitu- 

 tionally weak and feeble." Such, had they existed, would have been 

 surely eliminated in the life-struggle, and only the most vigorous and 

 robust left to migrate. The occurrence of the turnstone in Polynesia 

 and New Zealand, the sanderling in the Hawaiian Islands and Gala- 

 pagos Archipelago, the Siberian bar-tailed godait [Limosa uropygialis) 



