164 ANIMAL LIFE IN DESERTS 



unless the animal remains stiU. Abel Chapman has 

 gone so far as to state it as an axiom that " absolute 

 immobility, on the part of the object itself, is 

 essential ; to put it in other words that the slightest 

 movement, even of a part, is fatal to the value of 

 any protective principle." I think few of us would 

 agree to so extreme a statement, but every field 

 naturaUst knows that it is movement which catches 

 the eye more readily than colour, or pattern or even 

 symmetry. The Cream Coloured Courser {Cursorius 

 gallicus) is as perfect an example as one could find of a 

 bird which is invisible in desert, so long as it is still ; 

 sometimes it crouches and then it defies detection 

 in stony desert at 20 yards. More often it does not 

 crouch when you approach it, but gets on its long 

 legs and runs rapidly away ; it stands high above 

 the ground, casting a conspicuous black shadow in 

 the bright sunlight, and trusts to its legs and not 

 to its colour to ensure its safety. Even when it is 

 not disturbed the Courser is very conspicuous when 

 feeding in the early morning and late evening : as the 

 sun is low it casts a particularly large shadow, so 

 that at these times the bird is easy to see. The same 

 may be said of many other desert birds which are 

 beautifully "protected" if you see them in a 

 museum, but are quite conspicuous in nature 

 because they do not keep stiU. Most of the larks 

 of the Great Palaearctic Desert (Ammomanes, Gale- 

 rida and others) are rather fooHsh Httle birds which 

 scratch and feed and chirrup within 20 yards of you, 

 and you can only feel that a Httle ordinary intelligence 

 would render them invisible. Hey's Partridge {Am- 



