26 FLEAS, FLUKES AND CUCKOOS 



may also have some similar function. In any case it is a subject worthy 

 of further investigation in this country. 



In the previous chapter we have described birds which seek 

 protection by building in or near nests of termites and ants. We must 

 now consider an even more interesting nesting association between 

 certain birds and Hymenoptera in which both partners are thought to 

 receive protection. In South America, to take one example, the yellow- 

 backed orioles {Cacicus cela) — brilliant yellow birds, very conspicuous 

 in every way — build in colonies around one of the great wasp nests. 

 They place their nests so close to the wasps that when the tree sways 

 the homes of the insects and the bird rattle against each other in the 

 wind. Their presence keeps off the principal enemies of the orioles, 

 such as egg-thieving opossums, tree-snakes and monkeys. It was Myers 

 who first pointed out that the birds in a lesser degree also protect the 

 insects. Any accidental damage suffered by wasp nests is likely to be 

 by animals which have failed to notice their presence until too late. The 

 intruder, needless to say, regrets the episode just as keenly as the wasps 

 themselves. Brightly coloured birds grouped about the nest serve as an 

 advertisement which warns all and sundry from a safe distance that the 

 wasps are there. In other words once the birds become well-known 

 recognition-marks of the ensemble they serve as an additional warning 

 mechanism. Moreover, most, if not all, colonial nesting birds — of which 

 rooks are a fair example — keep a sort of permanent lookout or watch, 

 and at the first intimation of danger the whole colony is in an uproar. 

 It is probable that the unusual noise and movement also disturbs the 

 wasps. To be forewarned is to be forearmed, and it is no doubt of great 

 value to the insects to be made aware of danger before it is at close 

 quarters. This gives them the opportunity of driving off the enemies 

 before they are within reach of the nest itself. In Africa, as well as in 

 South America, some of the birds — although by no means all of them — 

 which are concerned in similar associations are both colonial nesters 

 and very conspicuous. 



It is only in fairly recent years that the nesting associations between 

 insects and birds have attracted much attention. The subject is excep- 

 tionally interesting and complicated and the reader is referred to the 

 original papers by Moreau and Myers listed in the bibliography. A 

 question which naturally occurs is this — do nesting associations of this 

 type, between wasps, bees and birds exist in Britain, which have hitherto 

 been overlooked ? The obvious place to search for such an incipient 



