shape and depth ; some are perfectly round, others oval, while a few are like 

 a railway tunnel, with a flat floor; they are usually two or three inches in 

 their largest diameter. At the far end of the excavation a round chamber, 

 some six inches in diameter, is made ; in this the nest is built. Many of the 

 holes turn and twist about to avoid boulders or other obstructions. 



About the end of May or the beginning of June the birds have begun 

 to lay, and this is the time for fresh eggs. Some colonies are very large, 

 and the face of the earth-cliff is riddled with holes in every direction. On 

 the approach of danger the whole air swarms with these little birds, and their 

 curious rattling twitter fills the air. They will fairly hustle an intruding bird 

 off the scene, chasing it with great pertinacity. Its flight is peculiar and 

 hesitating, and it seems to check itself every now and then as it flies 

 over the surface of the water. On the Broads in Norfolk I have seen them 

 sitting in thousands on the tall reeds, in company with House Swallows 

 and Martins. The eggs of the Sand Martin vary in number from four to 

 six ; they are pure white, sometimes faintly spotted with pale brown, which 

 however is easily washed off; they vary in length from 75 to '63 inch, and 

 in breadth from '50 to '46 inch. 



Two broods are reared in the year. As soon as the first broods are 

 capable of taking care of themselves they gather into large flocks and spend 

 the day in hawking after insects, roosting at night on the reeds and small 

 bushes in the marshes. The food of the Sand Martin is entirely composed 

 of small insects, especially gnats, which are most abundant in the neighbour- 

 hood of water. In the autumn, when they gather before migration, they may 

 be seen sitting in thousands along some line of telegraph wires, or on some 

 wire fence. I have seen the branches of a dead oak-tree covered by 

 thousands of these little birds. By the end of September most of them 

 have gone south, but a few stragglers may be seen well on into October. 



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