ANIMALS— PHYSICAL ENVIRONMENT 107 



place their nest as far as possible under shelter, 

 most Larks under a small bush, all Wheatears in a 

 hole or small cave, Hey's Partridge and See-See 

 (Ammoperdix) in holes in small cliffs, or under 

 boulders. Of the birds which breed in the open 

 without protection from rocks or bushes, most 

 species sit upon the nest from the time the first 

 egg is laid. The eggs are therefore kept at a nearly 

 constant temperature by the bird's body, and are 

 not exposed to the heat by day and the cold by 

 night. It appears to be established that Sand- 

 grouse incubate from the time of laying the first 

 egg, though Meade-Waldo's observations in an 

 aviary in England do not support this view. 



It is recorded that the Pratincole (Glareola pra- 

 tincola) stands over its first egg, and by doing so 

 protects it from the sun's rays, and that a small 

 Tern (Sterna saundersi) which breeds on the bare 

 shore at Karachi (Sind) does the same. 



After incubation has commenced the majority 

 of desert birds are unwilling to leave their eggs, 

 and if they are compelled to do so they return 

 to them as quickly as possible. This has been 

 noticed by several observers of the Coiu-ser (Cur- 

 sorius gallicus) and Sandgrouse. The eggs of the 

 Sandgrouse have additional protection from heat, 

 for when one parent returns from watering, and 

 reheves the other from the duty of incubation, its 

 breast is saturated with water. Therefore it appears 

 that the eggs and the soil on which they are laid 

 are wetted every day, which must tend to prevent 

 overheating. 



