76 BRITISH BIRDS. [vol. x. 



be felt forming on the wings when the young are about 

 eight days old, but they seldom show through the skin 

 until the tenth to eleventh day. There is such a differ- 

 ence in the size of the cocks and the hens that it is 

 possible to tell the sex almost to a certainty at ten days 

 old, especially if there are several young for comparison. 

 From the very earliest stage the young are instinctively 



Vig. 1. SPAEROW-HAWK. 



Young tweuty-five tla3S old ; three resting, while the fourth has just finished 

 preening. 



[Photographed by J. H. Owen.) 



cleanly. They back towards the edge of the nest and 

 eject the dung into the void below. At first the nest 

 gets spattered and the hen sees to this. Later the 

 limbs and tree below and around the nest get liberally 

 coated with whitewash. All the food that is swallowed 

 and not digested collects into pellets and these are 

 brought up and fall in the nest. These, too, the old 

 hen disposes of after each meal, sometimes, especially 

 in the earlier days, by swalloAving, and sometimes by 

 throwing them over the edge of the nest. In the later 



