22 FORM AND HABIT: THE WING. 



aquatic Grebes and Ducks, protected by tlie nature of 

 tlieir haunts and habits, lose all their wing-feathers at 

 once, and are flightless until their new plumage has 

 grown. 



It might then be supposed that permanently flightless 

 forms would be found among the Grebes and Ducks. 

 But these birds are generally migratory, or, if resident, 

 they usually inhabit bodies of fresh water where local 

 conditions or droughts may so afl:ect the food supply that 

 change of residence would become necessary. However, 

 on Lake Titicaca, Pern, there actually is a Grebe which 

 has lived there long enough to have lost the use of its 

 wings as flight-organs. 



Rails are such ground-lovers, and fly so little, that we 

 should expect to find flightless forms among them when 

 the surroundings were favorable for their develoj)ment. 

 In New Zealand, that island of so many flightless birds, 

 the requirements are evidently fulfilled, and we have the 

 flightless Wood Hens. Here, too, lives the flightless 

 Gallinule, NotornU, and in this family of Gallinules, 

 birds not unlike Coots, there ai-e at least four flightless 

 species inhabiting islands— one in the Moluccas, one in 

 Samoa, one on Tristm d'Acunha, and one on Gough 

 Island. The last two islands are about fifteen hundred 

 miles from Cape Good Hope, and have evidently never 

 been connected with a continent. There seems little 

 reason to doubt, therefore, that the ancestors of the 

 Galhnules now inhabiting these islands reached them 

 by the use of their wrings, and that these organs have 

 since become too small and weak to support their owners 

 in the air. Other cases might be cited ; for instance, 

 the Dodo of Mauritius among Pigeons, and the Kakapo 

 (Stringops) of New Zealand among Parrots ; but if the 

 illustrations already given have not convinced you that 

 disuse of the wdngs may result in loss of flight, let 



