42 ANNALS OF BIRD LIFE. 



very rarely extends its migrations to our islands, 

 although it breeds in the south of France, in Hol- 

 land, and in Germany. The White Wagtail and the 

 Blue-headed Wagtail are also common enough in 

 the meadows and on the banks of the streams on 

 the continental side of the Straits of Dover, yet 

 only accidentally cross over to England. These 

 two species, however, are specially interesting to 

 British naturalists, for it would seem that they are 

 gradually overcoming their continental prejudices, 

 and occasionally rear their young in this country. 

 Both should be eagerly looked for by British 

 field-naturalists. 



A far different spring-tide stranger is the 

 Alpine Swift, which pays us uncertain visits on 

 its migrations to the mountain districts of Central 

 and Southern Europe, where it rears its young. 

 This fine bird is an inhabitant of the mountains, 

 delighting in the ravines and passes, and show- 

 ing more preference for the rocky wilderness than 

 for the habitations of man. The occurrence of 

 the Isabelline Nightjar (an eastern species) in 

 England during the early summer, and of the 

 Red-necked Nightjar (a southern species) in 

 autumn, are events of exceptional interest to 

 naturalists, and at first sight seem very serious 

 exceptions to those laws which appear to govern 

 the seasonal movements of birds. Had the dates 

 been exactly reversed, there would have been 

 nothing extraordinary in the appearance of these 

 Nightjars. The most feasible explanation appears 



