RELATIVK VIABILITY IN MAMMALS AND BIRDS. 501 



Pivvi'ots are typically vegetarian birds, although, as is well 

 known, most of them do well if some animal material is added to 

 their diet. The intestinal tract is long and unusually complex, hut 

 it is narrow in calibre, there ore no C8eca, and the greater portion 

 appears to correspond with tlie small intestines, whilst there is 

 little that is used as a reservoir for waste matei'ial, or that can be 

 a probable seat of putrefaction. I cannot see that the indications 

 point towards their low viability being the result of their consti- 

 tution, and am disposed to attribute the relatively low maximum 

 and average durations to unsatisfactory conditions. The Zoolo- 

 gical Society has made experiments in recent years, in giving the 

 larger parrots free exposure to the open air, without artificial 

 heat. The experiment has not been of sufficiently long duration 

 to test the effect on longevity ; but even though the conditions 

 are not specially favourable in the particular aviary, the general 

 result appears to be good. I have no doubt that the ideal 

 management is a combination of ojDen-air flight cages with 

 sheltered, and quite possibly warmed retreats. 



Capt. Flower's- best records are a Bare-eyed and a Slender- 

 billed Cockatoo, still alive after 12 years' duration. As it was 

 only in 1898 that he took charge of the Giza Gardens and began 

 to make his records, about 12 years' duration was the maximum 

 possible. 



ACOIPITRES. 



FALCONIDiE. ?^°'.°f 



Pandion haliaetus (Osprey) 15 



Circtos, whole genus 23 



C. ceruginosus (Marsh Harrier) , 5 



G. cineraceus (Montagu's ,, ) 9 



C cyaneus (Hen ,, ) ...,,, 1 



C. gouldi (Gould's ,, ) 1 



C. macrurus (Swainson's ,, ) ....... 1 



C. viaurus (Moor ,, ) 6 



Buteo, whole genus 95 



B. albicaudatus (White-tailed Buzzard) 4 



Jj. augii7rdis (Augura ,, ) 2 



B. horealis (Red-tailed. ,, ) 11 



B. desertorum (African ,, ) 10 



B. erythronotus{KQ(i-ha.cked ,, ) 8 



B.ferox (Long-legged „ ) 4 



B. jackal (Jackal „ ) 11 



.i?. /)e?w?.sy/vamci(s(Pennsylvanian ,, ) 2 



B. poliosomus (Patagonian ,, ) 1 



B. vulgaris (Common ,, ) 42 



Archibuteo lagopus (Rough-legged 22 



Buzzard). 



Pernis ajjivorus (Honey Buzzard) ... 4 



P.pt dorhyncha (Crested Honey Buzzard) 1 



Proc. Zool. See— 1 91 1 . No. XXXIII, 33 



