98 THE entomologist's record. 



some previous butterfly or moth, in fact has found it so good as to 

 be worth a great expenditure of energy. (Confer, R. I. Pocock, loc. 

 cit., p. 811.) 



The sparrows in our garden (and probably in Mr. Colthrup's 

 garden, too) get more food than they can eat, and yet will go through 

 the most astonishing manoeuvres to catch Pieris rapae, Pieris brassicae, 

 and small Crambites, and will even try Sesia (3iatro//Zo.s.s<7) stellataruni 

 (and Biftton hirt'iria, apparently). I have seen Frhujilla codebs (the 

 Chaffinch) try S. stellataruni, and really it put up a good effort, seeing 

 that S. stellataruin can do 60 miles per hour at the least. 



This year we have had in one wood ten families of tits in nesting 

 boxes (about 130 head all told) — of course, just at the most interesting 

 period, business prevented observation. One pair, Panis viajor (the 

 Great Tit), came to the box (each bird) every five minutes with an 

 average of five larvae at a time, i.e., they brought about 120 larvae an 

 hour. One thing was very noticeable, the larvffi were nearly all green 

 larvae, very few brown. To my eye the green larva on the green leaf 

 is much easier detected than the brown larva on the brown twig. The 

 brown larvte are at least as abundant as the green larvae (actually more 

 abundant, but for my purpose equality will serve). If not better pro- 

 tected why are not more brought ? It looks to me much as if the 

 birds' range of perception were similar to mine, but more limited in 

 range. I might add also, from those numerous little indefinable 

 peculiarities of action, that in the long run produce such an impression 

 upon one, and yet are so difficult to put down in black and white as a 

 recorded observation [confer, R. I. Pocock, loc. clt., pp. 810 and 811), 

 the birds limit their purview to their immediate vicinity, and do not 

 trouble about things at a distance, even though those things be insects 

 on the wing. My conclusions therefore are : — - 



(a) That a bird's optical capacity is of the same nature as that of 

 a man. 



(6) That individually its optical capacity may be less critically 

 accurate in the form of the bundle of rays that the optic lens picks 

 up and transmits, or more accurate (as ej/., the Condor). This is a 

 question for the optical surgeon to settle by studying the individual. 



(c) That the bird's deductive capacity is probably inferior to that of 

 man, and certainly inferior in all-round capacity to that of trained 

 man [e.;/., entomologist), who recognises the sitting object as a moth 

 before movement betrays the fact of life. If this conclusion be correct, 

 it would nullify the supposed difficulty with regard to the slight 

 difterence in modes of flight existing between model and mimic on 

 which so much stress has been laid (see Proc. Zool. Sue. Lond., 1911, 

 p. 704). 



((/) That the bird concerns itself only with its immediate proximity 

 or its food area. In the case of small birds this will be close at hand, 

 and in the case of birds like the kestrel will comprise a larger area, 

 but the area, whatever it be, receives practically the undivided attention 

 of the bird. [Confer, H. T. Moule, "The Seemg Powers of Beasts and 

 Birds," Dorset Field Club Proc, 1902, p. 52, and Richardson on 

 " Missel Thrush," loc. cit., p. 86.) 



Before I leave these remarks I would like to point out to Mr. 

 Colthrup that Owls, Nightjars, and night-feeding birds (particularly 

 Oedicnemus scolopax, the Stone Curlew), and bats, have a vision modifiedi 



