RELATIVE VIABILITY IN MAMMALS AND BIRDS. 485 



Suiwrnai'ii of Passer es. 



The first general question that requires considei-ation is the 

 vahie of the data on which this summary is based. Passerine 

 birds, except to those who pay special attention to them as pets, 

 are relatively little individualized, and in a large collection it 

 may well be that the histoiy of one individual has been assigned 

 by mistake to another individual. I cannot doubt that such 

 mistakes have sometimes occurred, but I do not think that they 

 have had much effect on the figures. The bias they would give 

 would tend on the whole to lower the figures, for where there was 

 a doubt as to a dead individual in the Keeper's mind, I find that 

 he was disposed to assume that it was the oldest example. More- 

 over, if the figures be run through in detail, it will be found that 

 very often high records occur in cases where the number of 

 examples was so few that confusion of individuals cannot have 

 taken place, whilst the period of 33 years covered is so long in 

 proportion to the numbers in most cases, that probably this 

 source of error is on the whole insignificant. 



Mr. J. H. Gurney's remarkable paper* has already made plain 

 that birds attain considerable ages, and the figures of maximum 

 duration that I am able to record are in no case improbable. It 

 is to be remembered that probably the vast majority of 

 Passerines are received at the Gardens in an adult condition, 

 that the age of an adult bird cannot be determined from inspec- 

 tion, and therefore the maximum durations recorded are in all 

 cases below, and may be much below the potential longevity. Mr. 

 Gurney gives the following as the oldest Passerines of which he 

 had been able to obtain information : Raven 69 years, Gymno- 

 rhina tibicen, 26 years, Nightingale, 25 years. Skylark 24, Gold- 

 finch 23, Grosbekk 21, Canary 20, Bullfinch 19, Weaver-bird 9 ; 

 and he sets down 20 to 24 years as the possible limit of most 

 Passerines in captivity. Amongst the Garden records, I may 

 select the following : — Grey Struthidea, nearly 19 years. Paradise 

 Whydah Bird, over 16 years, Diuca Finch, nearly 16 years. 

 Glossy Starling and American Robin, about 13 years, Bay Cow- 

 bird, over 12 years, an Indian Crow over 11 years, a Bulbul 

 11 years, a Great Titmouse 9 years, a Lyre-bird, nearly 9 years. 

 Mr. W. Chamberlain, F.Z.S., informs me that he bought an adult 

 Cardinal (Paroaria cucullata) in 1874; that in 1896 it showed 

 signs of age, chiefiy difficulty with the autumn moult, and 

 thickening of the scales of the legs; that it died in 1899, 

 having lived in a cage for 25 years 4 months. It must be 

 noticed that if size be taken into consideration, the ages bear 

 no relation to the relative sizes of the birds which attained to 

 thera, and moreover that Passeres as a whole, in compai-ison with 

 their size, live to much greater ages than is the case with 

 mammals. This is entirely in accordance with the views of 

 Metchnikoff, for Passerine birds in every case have the hind-gut 



* "The Comparative Ages to which Birds live," Ibis, 1899, p. 19. 



Proc. Zool. Soc.~1911, No. XXXII. 32 



