486 DR. p. CHALMERS MITCHELL ON LONGEVITY ANB 



and cseca very small in proportion to the total length and cn.pacity 

 of the alimentary canal. They digest rapidly, void their excreta 

 at frequent intervals, and have very little opportunity for intes- 

 tinal putrefaction. 



With regard to viability, the recoixl of Passerines is on the 

 whole much better than in the case of mammals ; that is to say, 

 the maximum duration is frequently high and is much more 

 nearly approached by the average duration. There are some 

 notable exceptions. First, it is most striking that common 

 British birds, like common British mammals, have very bad lives 

 in captivity. I am inclined to put this down to the same kind of 

 reasons. In the first place, it must frequently happen that birds 

 are damaged by capture, or that many weak examples are taken, 

 and these find their way quickly to the Gardens, there to die ; 

 whereas in the case of birds captured in remote regions, the 

 deaths take place more frequently before arrival, and a selection 

 of the hardier individuals is thus made automatically. The case 

 would be moi-e striking if I had included in the averages, the 

 considerable number of birds that died without living for a month 

 at the Gardens, a number relatively much greater in the case of 

 common European and British forms. It seems, moreover, 

 highly probable, that wild birds in this thickly populated country 

 have survived in proportion to their development of a repulsion 

 to the vicinity of man, a repulsion which only a small proportion 

 of them, and that only gradually, can overcome in captivity. It is 

 most remarkable how the average duration of such kinds as 

 English Thrushes, Whinchats, Redstarts, Wheatears, Warblers, 

 Tits, Nuthatches, Pipits, Shrikes, Linnets, Finches, Buntings, 

 is from 12 months to 1 or 2 months, whilst that of their nearest 

 foreign allies may be many times greater. 



The viability, as shown by the average duration, has no 

 constant relation to size. On the whole, soft-billed birds, such as 

 the Tanagers, fed chiefly on fruit and prepared food, have been 

 less successful than Finches and Weavers, and insectivorous birds 

 have done less well than seed- and flesh-eaters. Nor is there any 

 striking result to be obtained from consideration of the quarters 

 assigned, for the vast majority of these Passerine birds have 

 been kept under similar conditions. The Western Aviary, with 

 open-air flights and heated retreats, has been their headquarters, 

 although some of the small Finches, Tanagers, and Weaver Birds 

 have been in cages in the Parrot House. The evidence points to 

 Passerine birds having a good viability and a potential longevity, 

 even in the case of the smallest, reaching well over twenty years. 

 Although success has been greater than in the case of many 

 mammals, I think that this is to be expected fi"om the constitu- 

 tions of these two sets of creatures, and that in proportion to 

 their viability, the success in the case of Passerines is still far 

 short of what might be achieved. Much has ali-eady been done 

 to improve the access to air in the case of all the Passeres. 



Capt. Flower's highest records are a Paradise Whydah Bii'd, 



