APPENDIX. 37 



* 



A golden eagle which ' died at Vienna in the year 1719, had been 

 captured 104 years previously' (Brehm, ' Leben der Vogel,' p. 72). 



A falcon (species not mentioned) is said to have attained an age 

 of 162 years (Knauer, ' Der Naturhistoriker,' Vienna, 1880). 



A white-headed vulture which was taken in 1706 died in the 

 Zoological Gardens at Vienna (Schonbrunn) in 1824, thus living 

 1 1 8 years in captivity (1. c.). 



The example of the bearded vulture, mentioned in the text, is 

 quoted from Schinz's 'Vogel der Schweiz,' p. 196. 



The wild goose must live for upwards of 100 years, according to 

 Naumann (1. c., p. 127). The proof of this is not, however, forth- 

 coming. A wild goose which had been wounded reached its 

 eighteenth year in captivity. 



Swans are said to have lived 300 years (?), (Naumann, I.e., p. 127). 



It is evident that observations upon the duration of life in wild 

 birds can only rarely be made, and that they are usually the result 

 of chance and cannot be verified. It is on this account all the 

 more to be desired that every ascertained fact should be collected. 



If the long life of birds has been correctly interpreted as com- 

 pensation for their feeble fertility and for the great mortality of 

 their young, it will be possible to estimate the length of life in a 

 species, without direct observation, if we only know its fertility and 

 the percentage of individuals destroyed. This percentage can, how- 

 ever, at best, be known only as an average. If we consider, for 

 example, the enormous number of sea birds which breed in summer 

 on the rocks and cliffs of the northern seas, and if we remember that 

 the majority of these birds lay but one, or at most two eggs yearly, 

 and that their young are exposed to very many destructive agencies, 

 we are forced to the conclusion that they must possess a very long 

 life, so that the breeding period may be many times repeated. 

 Their number does not diminish. Year after year countless num- 

 bers of these birds cover the rocks, from summit to sea line ; 

 millions of them rest there, and rise in the air like a thick cloud 

 whenever they are disturbed. Even in those localities which are 

 every year visited by man in order to effect their capture, the 

 number does not appear to decrease, unless the birds are disturbed 

 and are therefore prompted to seek other breeding-places. From 

 the small island of St. Kilda, off Scotland, 20,000 young gannets 

 (Sula) and an immense number of eggs are annually collected ; 



