l28 7he Irish Naturalist July, 



from other factors, when investigating a bird's flying 

 powers, hardly seems a satisfactory measure to go upon. 

 Indeed it is very likely that the shortening of birds' wing 

 is more often than not a secondary or adaptive modification 

 correlated with the mode of life when on the ground, but 

 not necessarily correlated with hindrance of considerable wing- 

 power when need for flight calls such into action. If there 

 were a strict proportional correlation between the shortening 

 of a bird's wings and the limitations of its flight, there is no 

 doubt that in the struggle for existence, unless the other 

 organs of locomotion, such as the legs of the flightless 

 Ratite birds, underwent considerable development, our 

 short -winged birds would have served very badly, if they 

 had not been wiped owiin toto. It is true that the penguins 

 have become flightless, but only in going through the air ; 

 what power of wing movements the}^ have lost in one 

 medium, they have gained in another, and we find them 

 flying through the water, in fact, undertaking vast submarine 

 migrations. Indeed, the penguin moves its limbs almost 

 as a fish when in water and a bird when on land, so per- 

 fectly does it command its two environments. It was 

 different in the case of the Great Auk, whose wings became 

 so markedty reduced and enfeebled (not merely by 

 shortening of the flight feathers, but by general reduc- 

 tion), that before these limbs could become metamor- 

 phosed into flippers, or some other more useful appen- 

 dages, to subserve its pronounced aquatic habits, the bird 

 met its fate by total extinction. Lack of compensation 

 for loss of flight is also evident in the case of the 

 Dodo ; had that land-bird developed its legs to a very 

 marked degree for climbing or running purposes, it might 

 have been still living. It seems that in the struggle for 

 existence the one great faculty above all others which 

 birds in temperate lands depend upon is the power of flight, 

 and this is made manifest in migration, which is the rule, 

 not the exception. If in temperate climes a bird cannot 

 hold its own without migrating, it is bound to go to the 

 wall. The abundant, hardy and adaptable House-Sparrow, 

 alike at home in the slum of the city, feeding on its garbage, 

 or by the country farmhouse, helping itself to the choicest 



