KEEPING THE EGGS COOL 155 



was very largely left to the sun, or to the heat 

 generated by the decaying weed in which the eggs 

 lay, for they were often both off the nest at all 

 and any times of the day ; and this habit of hatch- 

 ing otherwise than by constant incubation has 

 been often noticed. The Black-back Courser 

 (Pluvianus agyptius) of the African river-banks 

 buries its eggs in the sand and damps them to 

 prevent them getting too hot ; Sand-Grouse on the 

 plains of India have been found sitting on the eggs 

 not to warm them but to keep them cool, since 

 under the blazing sun they actually began to cook 

 if the birds were scared off for a little time ; and 

 the Ostrich has quite a reputation for letting the 

 sun hatch its eggs, though this only happens in the 

 more tropical part of its range — in South Africa it 

 sits like any other bird. 



Ordinary passerine birds may even in exceptional 

 circumstances make use of the sun as an incubating 

 agent ; in Hume's " Nests and Eggs of Indian 

 Birds " there is a record of a pair of House-Mynahs 

 {Acridotheres tristis) which built in a hole under the 

 edge of a roof fully exposed to the Indian hot- 

 weather sun, with the result that both of the pair 

 were always to be seen off the nest, the cock singing 

 vociferously and thrashing casual Crows after the 

 usual manner of his kind. 



There is a whole family of birds, allied to the 

 Game-birds, which carry matters further, and never 

 sit on their eggs under any circumstances, these 

 being the Megapodes or Mound-builders, referred 



