22 FORM AND HABIT: THE WING. 
aquatic Grebes and Ducks, protected by the nature of 
their haunts and habits, lose all their wing-feathers at 
once, and are flightless until their new plumage has 
wn. | 
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 affect the food supply that 
change of residence would become necessary. However, 
on Lake Titicaca, Peru, 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 wher 
the surroundings were favorable for their development. 
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, WVotornis, and in this family of Gallinules, 
birds not unlike Coots, there are at least four flightless 
species inhabiting islands—one in the Moluccas, one in 
Samoa, one on Tristan 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 
Gallinules now inhabiting these islands reached them 
by the use of their wings, 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 wings may result in loss of flight, let 
