RELATIVE VIABILITY IN MAMMALS AND BIRDS. 491 



MUSOPHAGID^. 



Turacus, whole genns 53 



^. &2f^b?«.t (Bafibn's Touracou) 5 



1\ corythaix (White-crested Touracou). 

 T. livingstoni (Livingstone's ,, ). 



T. macrorhynchus (Great- billed ,, ). 

 T. peisus (Senegal ,, ). 



T. schcdoioi (Benguela ,, ). 



Gallirex chlorochlamys (Green-necked 



Touracou), 

 G. porphyreoloplia (Purple-crested 1 19 19 



Touracou). 

 Musophaga violacea (Violaceous 7 17 44 



Plantain- eat ei-) . 



The Touracous and Plantain -eaters are frugivorous and 

 omnivorous birds with relatively simple intestines, the hind-gut 

 being reduced. Their viability, as shown by maximum and 

 average durations, is not good but surpasses that of the Cuckoos. 

 They have been kept under vai-ying conditions, always with 

 artificial heat, but in some cases with access to the open air. 



Simimary of Picarice. 



Picarian birds form a heterogeneous group, united by no certain 

 or close bands of affinity, and it is not surprising that their 

 relative viabilities and longevities do not correspond with their 

 gradations of size in any close fashion, although there is evidence 

 of such a general relation. The maximum duration recorded is 

 nearly 14 yeai\s for a Hornbill; then come a Toucan with nearly 

 12years,a Motmot and Barbet with 10 years, a Touracou with nearly 

 8 years, and a Kingfisher with 7 years. The conditions under 

 which these birds were kept during the period covered, have not 

 differed much. In the vast majority of cases they were kept in 

 houses or aviaries with artificial heat, but in some instances there 

 was access, at least occasionally, to open-air fiight-cages. I am 

 unable, however, to draw any clear inference with regard to the 

 effect of the mode of hou.sing from the facts at my disposal. The 

 very marked differences in viability exhibited, I think, must 

 depend largely on real constitutional differences between the 

 different suborders. The diet of the whole set tends to be mixed, 

 with a strong leaning towards carnivorous or insectivorous 

 character. The character of the alimentary tract varies con- 

 siderably within the assemblage, and I think a marked correlation 

 can be traced between the kind of gut and the viability. The 

 Caprimulgidae, Merof)idoe, Coraciidse, and Cuculidte have all 

 relatively capacious hind-guts and caeca, and in all these the 

 average duration is low, generally under a year, whilst the maxi- 

 mum duration is never high. The Mvisophagidse are generally 



