522 Dr. A. L. Thomson : liesults of a Study of [Ibis, 



the assumption that the individuals had left the respective 

 localities in the interval. There are two instances o£ Mallard 

 being found in a totally different area in subsequent summers, 

 but as all the other evidence points to the native birds of 

 that species being sedentary, the explanation of these as 

 exceptional cases, already suggested, seems to be justified. 



Return of Migrants to the same Winter- Quarters. — The only 

 definite evidence on this point rests on a single record and 

 refers to the Herring-Grull, a species which can scarcely be 

 regarded as a typical migrant. 



Winter -Quarters of Native British Birds. — The records for 

 a number of the species dealt with indicate, at least in part, 

 the winter-quarters of individuals which are summer visitors 

 either to the British Isles as a whole or to particular districts 

 therein. The small chances of obtaining records from, say, 

 northern Africa make it impossible to regard these indica- 

 tions as exhaustive. 



Summer -Quarter.^ of Winter Visitors to the Bintish Isles. — 

 The only very definite evidence under this heading refers to 

 the Starling {q. v.). 



Part taken in Movements hy Native British Birds. — As has 

 already been repeatedly pointed out, it is typical of migration 

 in the British area, which is a " half-way house " in Tem- 

 perate Europe, that species should be present throughout 

 the year, although known in autumn both as innnigrants 

 from the north and east and as emigrants to the south, and 

 vice versa in spring. Some light has been thrown on the 

 part played in these movements by the native British birds 

 of several species. More evidence is still required, but in 

 the cases of the Mallard and the Starling there is already a 

 strong presumption that the native birds are sedentary and 

 that any southward emigration which is observable must 

 therefore be on the part of birds that have already come 

 from more northerly or easterly summer areas. In other 

 cases, such as those of the Lapwing and the Woodcock, the 

 participation of the native birds is clearly proved. The 

 theoretical interest of the point has already been discussed in 

 the introduction. 



