APPENDICES 433 



dusk one sees the whole crowd "full-up" and all beaks 

 agape. 



No single section of animate Nature in the Sudan more 

 demonstratively illustrates the working of that principle, " The 

 Influence of Environment," than do the denizens of the Desert 

 Already in the chapters descriptive of the deserts are given 

 instances of wondrous assimilation between living creatures 

 and their inanimate surroundings the desert-larks, for example 

 (Certhilaudd) Pvrrhulauda, and Amommanes}. None of them, 



FINCH-LARKS (Pyrrhulauda). 

 " Cinderella of the desert." " The proud beauty of the corn-lands." 



however, recognise a protective value in their own coloration, or 

 attempt to exploit the quality as a personal safeguard. The 

 black-headed finch-lark (Pyrrhulauda) is a typical illustration. 

 On the rich cotton-soil this bird is richly arrayed in warm 

 chestnut and black; on the littoral barrens in neutral grey. 

 But on the open desert though colour-patterns remain 

 identical every vestige of a positive hue has vanished, 

 replaced by merely milky apologies for colour, faded and 

 washed-out in consonance with the surrounding Sahara. 

 One character, however, all three types retain the proud 

 beauty of the corn-lands and the faded Cinderella of the 

 desert alike. All are jet-black on under-surfaces and heads ; 



2 E 



