Ages to which Birds live, 27 



but artificial marks are of no value as an indication of age, 

 for the feathers of birds are continually dropping out and 

 wearing away. For this reason accidental varieties, e. g. the 

 pied Havens of Faeroe, cannot be trusted for many years. A 

 white-headed Turdus merula seen at Fethard for 15 years 

 (' Birds of Ireland/ i. p. 148) and another, seen at Barnard 

 Castle for 7 (Zool. 1866, p. 347), may or may not have been 

 the identical individuals which first revealed themselves, as 

 their recorders believed them to be. 



The following, by Mr. Joseph Whitaker, is very much to 

 the point, and may be adduced as bearing on this fallacy : — 

 " When once a variety has occurred there is always the chance 

 of its coming out again. For instance, in a rookery in 

 Leicestershire a few years back a white E,ook ( Corvus frugi- 

 legus) was hatched, and nearly every year since either white or 

 pied ones have occurred." (Norwich N. Tr. iv. p. 63.) These 

 latter were, presumably, the descendants of the albino or of 

 the albino's parents and it is evident that the first white 

 Rook detected may very soon have been dead. 



Still less is the fact that a Gypaetus barbatus in Switzer- 

 land or a Corvus corax frequented one secure precipice for a 

 quarter of a century, without any others of the same species 

 being seen, a proof that it was always the same individual. 

 Neither can we admit as more than presumptive evidence the 

 return year after year of such a bird as the Muscicapa grisola 

 to the same nesting-place. To show how unsafe this c(mclu- 

 sion would be^ Hawfinches {Coccothraustes vulgaris) nested 

 almost every year on a certain bough on an apple-tree in 

 Norfolk, though both the old birds were frequently shot (F. 

 Norgate, Norw. Nat. Tr. ii. p. 201), and therefore they could 

 not have been the same. 



In the same category is the evidence of the keeper of the 

 Bass Rock who " recognized from particular and well-known 

 marks certain " Gannets for upwards of forty years. (Selby, 

 Brit. Orn. ii. p. 457.) 



There are eight Orders of Birds about which I should like 

 to say something before beginning my List. 



