316 SWALLOWS AND MARTINS 



These valuable Tables, which might much more frequently be 

 imitated, not only illustrate the immediate point, but also the varia- 

 tion in the dates of the bird's movements from year to year. On 

 April 16, 1903, for instance, only 200 were roosting, whereas on the 

 same date of the next year there were a thousand. Again, on August 

 3, 1903, there were several thousands at the roost ; but on the same 

 date in 1904 the thousands had already set forth on their southward 

 migration, leaving a mere remnant of fifty to follow. More striking 

 still is the difference between the numbers at the beginning and the 

 end of the season, between the number that leave us in the autumn 

 and return to us in the spring a difference representing an appalling 

 mortality. 



Sand-martins, like their congeners and other species, notably 

 starlings, perform aerial evolutions before descending to their roost in 

 the reeds. They race about the sky in twittering bands, and then, at 

 a given moment, mount upwards, whirl this way and that, and on a 

 sudden fall like a shower into the reeds. Sometimes, instead of 

 settling down at once, they " skim to and fro in the waning light, with 

 rapid flight, just above the reeds, into which they suddenly and imper- 

 ceptibly vanish," J the only sign of their presence being the twittering 

 that continues for a time. 



This twittering song, pleasant enough when heard under such 

 circumstances, refined as it is by distance and the romance of the 

 twilight, is in itself of no great merit, and much inferior to that of the 

 swallow. In addition to its song, the bird has an ordinary low chirp, 

 and a louder, more penetrating cry of anger or alarm. These probably 

 do not exhaust its vocabulary, which has yet to be closely studied. 



Like swallows and house-martins, the present species suffers from 

 the attacks of the swifter hawks, their chief enemy being, according 

 to Naumann, the long-winged, quick-flying hobby (Falco subbuteo), the 

 terror of all the ffirundinidce, 2 Stoats sometimes succeed in getting 



1 T. A. Coward, op. cit. s Vijgel Mitteleuropas, iv. 220. 



