Birds in Relation to their Prey. 99 



were completely nauseated, and, after much straining, 

 vomited up all that they had eaten of the offending butter- 

 flies. This was in experiment 507. In 511 was similarly 

 nauseated by an Amauris. But many othsr butterflies were 

 eaten without the slightest apparent ill-efEects. Here we at 

 once have an opening for such preference as we suppose 

 our 8hrike to have shown. A similar contrast in after- 

 effects is to be found in every insect order, and a similar 

 inability to eat low-grade insects without nauseation beyond 

 a certain point in the process of repletion has been evinced 

 by ninnerous species of birds beside Wood-Hoopoes. Even 

 Loplioceros leucomelas A showed great uneasiness after having 

 eaten the brilliant strong-smelling moth-larva of experi- 

 ment 520, and refused another with anger ; and again 

 apparently somewhat overstepped the safety-limit in experi- 

 ment 521 and, probably, 526. These instances were in 

 relation to Acrcva. B did the same in relation to Amauris. 

 AVhether her eating of earth after her Danaidas of experi- 

 ment 531 indicated a similar condition it is not easy to say. 



It is a curious fact^ nevertheless, that even those birds with 

 the smallest capacity for eating nauseous insects are able to 

 eat one or two with apparent impunity, and even eagerness, 

 when their stomachs are empty and appetite good. Thus 

 the average bird may quite readily eat Uanainffi or Acrasince 

 several times in the day — in the early morning or after some 

 other long interruption to feeding and after the ejection 

 of each pellet. As it fills up somewhat, it rejects such, very 

 low-grade prey, but eats other species, some of which, in 

 time, it finally rejects when slightly fuller, though still eating 

 the others. And so, through the successiA^e elimination of 

 many grades, right up to repletion-point. The main dif- 

 ference between Loplioceros (and Bucora.r) and the more 

 normal birds I have experimented on is that the Hornbills 

 are able to acce})t and digest such insects as Danaida and 

 Acr(ca in larger numbers and up to a far later stage in the 

 filling of their stomachs. Once, however, they reach the point 

 at which such insects become unacceptable, their preferences 

 follow the course of most other birds. First the Danainoe 



