20 THE HUMAN SIDE OF BIRDS 



bee-eaters, and their cities are marvels of beauty 

 and careful workmanship. Each bird knows his 

 own residence, although they all look exactly alike, 

 and in a surface of twenty square feet there are no 

 less than fifty to sixty square holes. These little 

 workmen constantly fly in and out in a never-end- 

 ing stream, like a hive of bees. Surely no city 

 could have a better example of brotherly kindness 

 and consideration than is seen in these bird cities! 

 Each individual seems thoroughly to respect the 

 rights of his neighbours, and happiness reigns 

 everywhere. 



Not all of the burrowing birds follow the usual 

 ways, however, for occasionally one may see them 

 nesting on a brick wall, or on high rocks. And 

 sometimes, even the sand martins, who in Pliny's 

 time seemed to delight in sand-digging and bur- 

 rowing, will return to their almost-lost art of build- 

 ing mud-houses. Nuthatches often build houses 

 by burrowing into decayed trees ; and the Assjrrian 

 nuthatch makes a mud-house under a wall with an 

 additional mud vestibule. Thus we see that these 

 ancient nuthatches are in reality masons. 



A most interesting belief prevails in the Outer 

 Hebrides relative to the "hot chamber" where 

 young petrels are hatched. The inhabitants claim 

 that the birds hatch their eggs not by sitting on 



