NESTS AND NEST-BUILDING IN BIRDS 369 



that both use the bill as pick, and scratch out the detached earth 

 with their feet. Both drive a straight or inclined tunnel of 

 fairly uniform dimensions, and excavate an arched chamber at 

 the end, although unlike the martin the kingfisher carries in no 

 nesting materials, the fish bones or crayfish shells which are found 

 in its chambers representing the disgorged remnants of its food. 



The nesting habits of the American eaves swallow {Petro- 

 chclidon lunifrons) and the European house martin {Chelidon 

 urbica) appear to be similar in essential respects. In the former 

 a retort-shaped shell of clay or mud is glued to the steep sides 

 of rocky cliffs or under the ea^'es of buildings, a short symmet- 

 rical entrance tube being built out opposite the side of attach- 

 ment. The " retort " has a beaded appearance over its entire 

 surface, being composed almost wholh^ of rounded pellets laid 

 one at a time, when moist, and presumably mixed with a certain 

 amount of saliva, the chamber thus formed being e\'entually 

 lined with grass and feathers. According to Gilbert White " 

 the English house martins fix the pellets of which their nest 

 is similarly composed by the aid of their chins, " moving their 

 heads with a quick vibratory motion." Usually building to 

 a northeast or northwest aspect, they are at ^^'ork before four 

 o'clock in the morning, but as White remarks in another place, 

 " that this work ma}^ not, while it is soft and green, pull itself 

 down by its own weight, the provident architect has prudence 

 and forbearance enough not to advance her work too fast; 

 but by building only in the morning, and by dedicating the 

 rest of the day to food and amusement, gives it time to dry 

 and harden. About half an inch seems to be a sufficient layer 

 for a day." From lo to 12 days are usually occupied in building 

 this mud nest. 



The South American oven bird {Funarius) in rearing its 

 arched chamber of mud, dung, and grass, is said to pause fre- 

 quently in the work in order, as we are told, that its mortar 

 may set and harden before proceeding to spring the arch and 

 mold the roof. I have noticed that some of the mud-daubing 

 wasps do not work continuously at their clay-tubes, which thus 

 stiffen to some extent before they are completed, and we do 

 not consider such behavior in bird or insect as indicati\'e of 



« Ibid. p. 134. 



