288 SWALLOWS AND MARTINS 



this way and that in pursuit of their insect prey, represents an 

 astonishing output of energy. More than most birds, therefore, they 

 must suffer from failure of their food supplies. A spell of severe frost 

 occurring after their arrival will kill thousands, the fruitless chase 

 after food adding fatigue to starvation, and still further reducing their 

 ability to resist the paralysing grip of the frost. At these times they 

 search the surface of water for anything they can find, and swallows 

 have even been seen clinging to the walls of houses or out-buildings, 

 picking the remains of flies from spider-webs, and adding the spider 

 itself as sauce to their desiccated repast. 1 



It is not only in hard weather that the two species seek their food 

 elsewhere than in the air. At all times they may be seen picking 

 insects off the surface of ponds or rivers, often dipping their breasts 

 into the water as they do so. Both occasionally settle on the ground, 

 either to swallow grit, to aid the trituration of their food on the gizzard, 

 or to pick up insects. Lord Lilford relates that more than once he 

 saw a vast assemblage of martins on the gravel in front of his house 

 engaged in devouring minute black winged insects which covered the 

 ground. 2 No swallows took part in these feasts, a fact which seems 

 to indicate that the two species differ more or less in their diet. 

 Swallows appear to have developed to a greater extent than martins 

 the habit of taking insects from the blades of grass as they skim along. 

 They also pick them off walls, trees, and bushes. 3 One has been seen 

 to hover in front of a horse, and then pick a fly off its shoulder. 4 Their 

 habit of accompanying cattle, horses, carts, and haymakers, in order 

 to snatch their attendant flies, is well known. As long ago as 1774 

 Gilbert White records, in his letter to Barrington of 29th January, that 

 " horsemen on wide downs are often closely attended by a little party 

 of swallows for miles together, which plays before and behind them, 

 sweeping around, and collecting all the skulking insects that are 

 roused by the trampling of the horses' feet; when the wind blows 



1 Bailly, Ornitholoffie de la Savoie, i. 246. - Lilford, Birds of Northamptonshire, i. 243. 



J Ornis, x. 149 (P. Prevost). ' Zoologist, 1870, 2307. 



