REPRODUCTION— NIDIFICATION 177 



fragile Bee-eaters and Sand-martins, the beak alone is employed 

 in digging, but the feet eject the loose earth, the feet indeed 

 of these birds being remarkably small and delicate. The two 

 last-named species, for their size, bore really remarkably long 

 tunnels, those of the Sand-martins extending in an upward 

 direction for a distance of four or five feet, or even longer, when 

 the tunnel terminates in a chamber of some six inches in 

 diameter, the floor of which is covered with a little grass, or, if 

 near the sea, with sea-weed and a few feathers. Both sexes 

 combine in the work of excavation, which is carried on only 

 during the early hours of the morning. Bit by bit the soil is 

 removed, and often when the work is almost half-way through 

 a stone will be encountered, and if this be too large, then there 

 is nothing for it but to make a fresh start in another place. 

 Once completed, however, the burrow is used year after year. 

 The sides of a sand-pit are chosen for preference, but the 

 middle of a bluff a hundred feet high, or a thin layer of mould 

 of some eighteen inches thick, capping the side of a chalk- 

 cutting, will serve the purpose equally well. Nay, further, they 

 will, as in Norway, utilise the turf-roof of a hut, or a hole in a 

 wall, and they have been known to take advantage of huge 

 heaps of sawdust ! That most enthusiastic naturalist Waterton 

 even induced them to take possession of a series of drain- 

 pipes. 



The common Kingfisher, unlike the Sand-martin, is a 

 solitary bird. Whenever possible choosing the deserted burrow 

 of a water-vole, it will, when such a ready-made tenement is 

 not to be had, dig for itself According to some indeed this 

 practice is invariably followed. The length of the burrow is 

 roughly about the same as that of the Sand-martin, and simi- 

 larly this terminates in a wide chamber, which, as we have 

 already stated, is soon covered with a layer of fish-bones and 

 other indigestible matter ejected by the builders, and on this 

 the eggs are laid. Though in course of time this mass gets 

 beaten down and forms, by the adherence of the debris, a more 

 or less coherent mass, no real nest is ever built by these birds. 



It would seem, as we have already remarked, that nest- 

 building had its origin in an attempt to secure comfort in brood- 

 ing where the eggs were laid on cold or damp ground. This 

 being so, it is easy to understand how birds which had thus 

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