135 [Vol. XXXV. 



atmosphere, species from a humid climate being usually 

 darker in colour than allied forms inhabiting a dry region. 



Dr. Hartert has especially mentioned the case of the 

 Crested Larks, which appear to vary their coloration 

 according to the colour of the soil upon which they are 

 founds instead of following the general rule and becoming 

 dark in a moist climate. 



A somewhat parallel case is that of the Bustards, Chlamy- 

 dotis u. undulata and Chlamydotis u. fuerteventurae. The 

 former lives on the mainland of Africa and is an inhabitant 

 of sandy wastes in Morocco, Algeria, and the Sahara. Its 

 plumage is of the usual colour found in desert-frequenting 

 birds and, following out the theory of colour-protection, 

 this bird accords exactly with the ground over which it 

 roams. This Bustard at some remote period presumably 

 crossed from the Moroccan coast to the Canary Islands, 

 and the first land which it sighted was naturally the most 

 easterly island, Fuerteventura, for there is no evidence to 

 prove that this island, though lying only 60 miles out 

 to sea, has ever been joined to the mainland. In Fuerte- 

 ventura the Bustard found ground well adapted to its 

 requirements — a low flat desert island very similar to the 

 African deserts which it had left and, be it remembered, 

 in exactly the same latitude. Moreover, Fuerteventura is 

 one of the driest islands in the world and has an exceedingly 

 small rainfall. There is, however, one great difference 

 between it and the mainland which, though not affecting 

 the climate, does aff'ect the external appearance of the 

 island. Fuerteventura is volcanic in origin, and the bare 

 plains are dotted and strewn with lumps of blackish lava, 

 often half buried in the sandy soil. 



When the African Bustard first found itself on this 

 ground, its light plumage no longer harmonised with its 

 surroundings — in fact, the one character which contributed 

 to its protection in the African deserts made it conspicuous in 

 the Fuerteventuran waste. It therefore modified its plumage 

 to the extent you now see, and in course of time harmonised 

 exactly with its darker surroundings. This example is a 



