244 THE MIGRATION OF BRITISH BIRDS 



areas cast and north of them. This migration in spring 

 is much less marked than in autumn, and for three 

 reasons. First, it is always more difficult to note the 

 departure of a migratory species than to observe its 

 arrival ; second, the number of individuals that depart 

 in spring is very much less than the number that arrived 

 in the previous autumn, owing to the casualties of the 

 intervening winter ; and third, the majority of the 

 species that take part in the movement are birds that 

 breed commonly in our area, and it is difficult if not im- 

 possible to distinguish between the individuals that only 

 winter here, and those that spend the summer with us. 



This migratory movement, in a fairly normal spring, 

 may be said to commence as early as February, and the 

 first migrants to go are those that breed in continental 

 areas east of the British Islands. Amongst these species 

 we may include the Missel Thrush and the Song Thrush, 

 the Hedge Accentor, various species of Titmice, the 

 Wren, the Linnet, and some other Finches, several 

 species of Bunting, the Jay, the Rook, and the Carrion 

 Crow. In former years, when the Great Bustard and 

 the Bittern were common in our islands, these species 

 also would have been amongst the first migrants to 

 move towards the Continent. The indication of their 

 migration is now very slight. For a complete list of the 

 species partaking in this early spring migration the 

 reader is referred to the table on p. 132. The next 

 species to move out of our islands are those whose lines 

 of Migration trend north-east. It is impossible to 

 separate the individuals, but many birds of these species 

 migrate both east and north-east ; those travelling in 

 the latter direction are the last to go. Among these 



