I 



RELATIVE VIABILITY IX MAMMALS AND BIHUS. 537 



Flamingoes have a potential longevity certainly considerably 

 over 20 yeai-s, and have a high viability in captivity. 



Screamers appear to have rather low potential longevity and 

 viability, certainly much lower than those of Flamingoes or 

 Geese. 



Swans, Ducks, and Geese have a longevity most probably going 

 beyond 50 years, and appear to have a good viability. 



Doves and Pigeons have a potential longevity certainly 

 reaching to about 30 years and have a veiy good viability. 



Sand-grouse apparently are considerably lower than Pigeons 

 both in potential and average duration. 



Gallinaceous birds ha,ve a potential longevity ranging about 

 20 years, and only a fair viability. Megapodes, Ourassows, and 

 Guans seem to be most hardy and the longest livers. 



The Hemipodes have considerably lower potential longevity 

 and viability than Gallinaceous birds of about the same size. 



Rails, Crakes, Porphyries, and Gallinulee appear to have poten- 

 tial longevities of not more than about 20 years, and have 

 relatively low viability. 



Of the Alectorides, Cranes have a potential longevity almost 

 cei-tainly exceeding 50 years and a very good viability. 

 Kagus have a still better viability and probably a somewhat 

 similar potential longevity. Bustards are the lowest of the group 

 both in longevity and viability. • 



Limicolous birds have a potential longevity wdiich is high in 

 proportion to their size and must be set down as at least about 

 30 years. Either their constitutional viability is low or the 

 conditions of captivity are specially unfavourable to them. 



Gulls aiid their allies certainly have a potential longevity of at 

 least 30 years, but their viability, at least undei' the conditions 

 of captivity, is relatively low. 



Puffins, Divers, Guillemots, and so forth have so poor a via- 

 bility in captivity that no conclusions can be drawn as to their 

 potential longevity. 



Penguins have a potential longevity of at least OA^er 12 years, 

 but their viability under the conditions of captivity, in the period 

 covered by iny records, is low. 



Tinamous appear to have a low potential longevity, certainly 

 not much over 12 years, and a relatively poor viability, 



The potential longevity of Strnthious birds is certainly under 

 50 years, and then- viability is relatively low. 



Longevity mid Size. 



A very summary inspection of the tables of figures I have 

 given will show that foi- birds as a whole there is no constant 

 i-elation betw^een potential longevity and size. The correlation 

 does not exist even if only size and actual longevity be taken. An 

 Ostrich is much bigger than a Crow or a Pai'rot, anil yet cannot 



