Ianuary 17, 191 8] 



NATURE 



185 



The Supposed "Fascination" of Birds by Snakes. 



1 HAVE been making further inquiries from my 

 naturalist friends, and find Capt. G. D. H. Carpenters 

 observation recorded in Nature of November 29 last 

 (p. 244) is confirmed, together with the interpretation 

 there suggested. 



Dr. G. A. K. Marshall writes: — "The mobbing of 

 snakes by small birds, and even by fowls, was fre- 

 quently mentioned to me by residents in South Africa, 

 and my general impression is that I have observed it on 

 various occasions without specially noting it, and 1 

 cannot now recall the details of any particular case." 



Mr. S. A. Neave, with a wide African exf>erience, 

 felt that the facts recorded by Capt. Carpenter were 

 familiar to him, and associated in his mind "with par- 

 ties of small finches and weaver birds in open, grassy 

 places," but he was unable to remember any particular 

 instance. 



Mr. J. C. Kershaw, for a long time resident in 

 Macao, China, and a traveller in the Malay Archi- 

 pelago, Australia, and the West Indies, writes : — " 1 

 have often seen snakes pursued and annoyed by birds, 

 just as cuckoos and hawks are by small birds, but 

 never saw any sign of ' fascination ' by the snake to 

 obtain prey." 



Mr. Kershaw has observed the mobbing of all kinds 

 of snakes, and in many countries. " In China Lanius 

 schach and Dryonastes perspicjllatus especiaWy raised an 

 outcry over snakes. I remember one day hearing sorrle 

 shrikes (L. schach) making a great hubbub in a tall, 

 thick bush; investigating, I found a snake (some 

 6 ft. or 8 ft. in length) in the upper part, and threw a 

 clod of turf at it, striking it (by a fluke) about the 

 middle of the body. The shrikes ilew off, but the snake 

 remained motionless for nearly half a minute, and 

 then suddenly darted off. The" light clod could not 

 have really hurt it." 



Mr. J. Williams Hvockin, with a very long experience 

 of South India, writes: — 'The only case of birds v. 

 snake I can remember is seeing a cobra attacking the 

 nest of a ground thrush in a coffee tree at 3 ft. from 

 the ground, and being clamorously assailed bv the 

 parents." A little later my friend kindly supplied fur- 

 ther details of his observation : — "The cobra attack on 

 ground thrushes (Geocichla, the slate and buff, not 

 Pitta, the ruddy and kingfisher blue one) occurred in 

 the Ellembelary Coffee Estate, three miles from Mep- 

 padi Village, in Malabar Wynaad, at an elevation of 

 3500 ft. So far as I can remember, it was eggs and not 

 young birds the snake was after, but I cannot be sure. 

 It was between 1894 and 1899. As you suppose, I was 

 more humanitarian than scientific in those days, and 

 got off my horse and went into the coffee to drive the 

 snake off. The nest was on the top of a tree about 

 3 ft. high, the top forming, with those around it, a flat 

 sheet of coffee. The snake was round the stem with 

 its head over the edge of the nest, and the parent 

 birds on each side, shrieking for all they were worth 

 and fluttering round about on top of. the boughs. On 

 my approach the snake glided away, and the coffee was 

 too thick for me to get at it. I do not think it took 

 anything. The coffee in Wynaad was topped at 3 ft. 

 or so, and all suckers removed when they appeared, so 

 as to keep an even sheet of cover on the ground." 



Not one of the above-named naturalists had seen 

 anything like the traditional "fascination" of birds by 

 snakes. Mr. F. Muir, however, told me that he had 

 seen a bird^ — I believe in East Africa — sitting on a 

 branch with its bill open and unable to move, while 

 a snake approached and swallowed it. This may be an 

 instance of " fascin?ilion." Weak-minded birds may 

 sometimes act in this suicidal manner, just as some 

 human beings may be paralysed by fear and unable to 

 NO. 2516, VOL. 100] 



! defend themselves or to escape from danger. But 

 ] another interpretation is suggested by the following 

 I extremely interestmg observation recorded by Dr. 

 I G. A. K. Marshall: — "When happening to look over 

 i a low stone wall near Estcourt, Natal, in 1897, I 



chanced to observe a small snake in the very act of 



striking a frog. After being bitten the latter hopped 

 I off at a great pace, and I was rather surprised to see 

 I that the snake made no attempt at pursuit, but merely 



followed in a very leisurely manner. Seeing that the 

 1 frog had come to a standstill at a considerable distance 



off, I crept along under the wall, so as not to disturb 

 ! the snake, and on getting near the frog I looked 

 j cautiously over the wall to see the end of the tragedy. 

 I The snake was still some way behind, approaching 

 I steadilv, and on reaching its victim stood watching it 



for some moments with its head raised, the frog mean- 

 I while sitting trembling in front of it. At last the 

 I snake seized its prev, ard succeeded in swallowing it 



after but feeble resistance. It seemed clear that the 



trembling and inability to escape on the part of the 

 ! frog were simplv due to the action of the poison in- 

 i jected at the snake's first bite. It immediately occurred. 



to me that these observations might supply a simple. 



explanation of manv of the stories of ' fascination ' by 

 I snakes." Edward B. Poulton. 



, Oxford, January 2. 



THE SCIENTIFIC BASIS OF RATIONING. 



AN ideal ration is one which provides the adult 

 with sufficient potential energy to meet all 

 the demands made by the organs of his body for 

 transformation into the kinetic form, and enough 

 building material to make good the wear-and-tear 

 of essential cells ; a complete ration for children 

 and adolescents must also make provision for the 

 requirements of growth. Three methods, of deter- 

 mining the quantities needed to fulfil these con- 

 ditions are available. The first is to follow as 

 closely as possible the system of an engineer, viz. 

 to study the efficiency of the human machine as 

 a transformer of energy when measurable amounts 

 of work are performed under determinate con- 

 ditions. The second is to measure the total energy 

 transformed by the body under various con- 

 ditions, also determinate, although not necessarily 

 permitting of an eiact evaluation of the amount 

 of mechanical work done. Lastly, when it is 

 neither possible to measure directly the energy 

 transformed nor to evaluate the work done, the 

 composition of diets consumed by samples of men 

 engaged in different occupations throws light upon 

 j the probable needs of different classes. 



These methods have been enumerated in a de- 

 scending order of importance so far as the 

 accuracy of the information which, under favour- 

 able conditions, they might yield is concerned ; so 

 far as practicability is involved, under normal con- 

 ditions of life, the order is reversed. We shall refer 

 ; briefly to the data available under each heading. 

 ! (i) The only type of work respecting which 

 I numerous and exact measurements both of energy 

 : transformed and of external work done are avail- 

 • able has been that carried out with a stationary 

 I bicycle, the wheels of which are rotated against 

 : a known resistance. The best series of experl- 

 j ments is due to Benedict and Cathcart,i whose 



i "Muscular Work : a Metabolic Study." (Washington, 1913.) 



