158 ARTISTS AND ARTISANS IN THE J^EATHERED WORLl). 



sufficiently firm to escape the likelihood of breaking 

 down. The depth of the tunnel is extremely variable, 

 some tunnels being only eighteen inches or two feet 

 deep while others run to a length of nearly five feet. 

 In excavating its domicile the sand martin displays won- 

 derful activity and ingenuity, and abandons itself to its 

 work with a thorough recklessness of enjoyment. Cling- 

 ing to the face of the rock, it delivers thereon a firm 

 sharp blow with its closed beak, as if to test the quality 

 of the material, and then nimbly runs or flutters to an- 

 other spot where it repeats the same process, until it has 

 fixed upon some suitable locality. It then fairly sets to 

 work, and by dint of repeated blows in the same spot 

 loosens a considerable piece of soil, which comes tumbling 

 to the ground. The bird then cuts a circular, funnel- 

 shaped depression by running around the circumference, 

 and working from the centre outwards, and in wonder- 

 fully short lime succeeds in forming a well-defined circu- 

 lar hole. Having made so much progress, it rests for a 

 short time and then redoubles its ardor, chipping away 

 the stone or sand with repeated blows of its bill, and 

 cleaning the fallen material with its claws. This seems 

 the most fatiguing part of the work, as the earth must, 

 as soon as the tunnel gets longer, be pushed or carried 

 a considerable distance from inside before it can be 

 dumped over the edge. Both mates help each other in 

 the most charming way. As a strange fact it must be men- 

 tioned that these birds are not readily satisfied with one 

 locality, and being in no wise sparing with their labor, 

 will often dig three or four holes before they will make 

 a final settlement. The burrows are generally straight 

 unless turned out of their course by some impediment, 

 but in all cases they are slightly globular at the extrem- 

 ity where the nest is deposited and slope gently upwards, 

 so that the eggs and young cannot be inundated by rain. 

 The sand martin is very gregarious in its habits and 



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