20 Mr. J. H. Gurney — Comparative 



migration, whicli doubtless dash them into the sea in 

 hundreds every year. 



Because of these perils, it may well be believed that not 

 one bird in fifty reaches its full possible duration of life, 

 perhaps not one in two hundred. However^ the subject for 

 discussion in this article is not the average age to which 

 birds commonly live, but rather the full extent of age to 

 which they can live, all things being in their favour ; but 

 both divisions of the subject are interesting, and I am sur- 

 prised that no recent writer has inquired into them. 



The great Lord Bacon (b. 1561), in his treatise on ' Length 

 and Shortness of Life in Living Creatures,' had a great 

 deal to say about the age of birds, and concluded that more 

 kinds were found to be long-lived than of beasts, setting 

 forth various reasons why this was probably so. He par- 

 ticularly lays emphasis on the mixed motion of birds in their 

 flying, as being a kind of exercise conducive to longevity, 

 which is denied to beasts, and he assigns to several sorts 

 what was believed to be the maximum of their longevity 

 in his day, and really we do not know much more about it 

 now than he did then. 



Willughby and Ray (1676) devote a chapter to " The Age 

 of Birds,'' which shows that attention had been turned to 

 the subject by older authors than themselves, like Aldro- 

 vandus. Something also may be found in Philos. of N. H. ii. 

 p. 416, and in 'Domestic Habits of Birds,' 1833, from the 

 pen, I believe, of Prof. J. Rennie ; but the literature of the 

 subject in modern times is very scanty, though a certain 

 number of incidental notices are scattered about such journals 

 as 'The Field' newspaper and 'The Zoologist.' 



In Thompson's 'Birds of Ireland' (1851) there is a useful 

 article, and in 'The Naturalist' for 1897, p. 129, there is a 

 paper by Mr. Oxley Grabliam on "Owls and their Longevity." 

 Allusion should also be made to Mr. W. B. Tegetmeier's 

 article on " Length of Life in Zoological Collections " 

 ('The Field,' June 5th, 1869), and to some notes in the late 

 Lord Lilford's two articles on "Raptorial Birds in the 

 Lilford Aviaries," Norwich N. Trans, iv. p. 564, v. p. 128. 



