526 



The Scarcity of Swalloavs. 



[Sept., 



THE SCARCITY OF SWALLOWS. 



Henry Boase. 



This summer the scarcity of swallows and the martins has 

 been a subject of general remark, and various theories have been 

 put forward as to the reason of the scarcit3^ Some of these 

 theories have been rather fantastic, and a few notes on the sub- 

 ject may be of interest. 



Some of the factors which may affect the numbers of these 

 birds have been examined and a general statement has been pre- 

 pared. In doing so it has been thought advisable to include the 

 swift with the Hirundince, as a general similarity of its feeding 

 habits causes it to be affected by some of the conditions which 

 may influence the distribution of the swallow and its relatives. 

 The four birds (swallow, martin, sand martin, and swift) are at 

 tim.es referred to hereafter as a group, but it must be under- 

 stood that this is a matter of convenience only. The swift has 

 no relationship with the Hirundines and differs in many import- 

 ant features of structure and habit, but, feeding in the air in 

 common with the three true Hirundines, it may be considered 

 along with them in that connection. 



These notes express the situation as gathered in Scotland, re- 

 presenting a point of view rather than an authoritative statement, 

 and are not intended to represent any degree of finahty in so 

 complex a matter. 



Certain general features call for some explanation, and accord- 

 ingly an account of certain aspects of habit is given in order to 

 make clear the ideas put forward in connection with the reduc- 

 tion of numbers. 



Food Habits. — As a group, these birds are remarkable for the 

 manner in which they feed. Practically all their food consists 

 of winged insects secured in flight : in the swallow only have I 

 noticed any attempt to secure insects on the ground. Some are 

 also picked from the surface of still water while the bird is 

 drinking or bathing, but these represent a very small proportion 

 of the total quantity consumed. All members of the group seem 

 to spend their time almost solely in obtaining food. The 

 swallow and martins appear to hawk around the neighbourhood 

 where the nest is situated, and seldom wander unless under 

 stress of weather. In high wind, the flight of th-e insects on 

 which they feed is naturally impeded, and the insects tend to 

 gather in sheltered places, in the lee of woods., In hollows, etc., 

 and are pursued there by the birds. All the Hirundines seem 



