PARASITIC HABITS OF THE INDIAN KOEL. 781 



Firstly, as regards the plumage of the nestling. Its skin is invariably black 

 and in each of the twelve koel nestlings, whose early life-history I followed, 

 the earliest feathers to appear were not pure black but were tipped with 

 white or a kind of reddish fawn colour. The nestlings that had the white 

 tips to their feathers were undoubtedly females, for all their subsequent 

 feathers were barred. But I am not at all sure whether the converse is true, 

 viz., that all birds whose earliest feathers are tipped with reddish fawn are 

 cocks. In two cases the first wing and tail feathers to appear were alone thus 

 tipped, so that before the young cuckoo left the nest it was almost as black as 

 the adult. But many of the birds which had reddish tips to their feathers 

 were subsequently barred to as great an extent as the undoubted females. 

 Were these hens or very much barred cocks ? I am inclined to take the latter 

 view, since even in the two undoubted cocks one was more conspicuously 

 barred than the other. If this is correct then the test of the sex of a nestling ia 

 not so much the extent of the barring of the feathers as the colour of the bars. 

 There were three undoubted cocks among the birds on which I experimented, 

 that is to say, three that were black almost all over when they left the nest and 

 four undoubted hens, i.e., that were very heavily barred with white when they 

 left the nest. In addition to these there were two much barred birds with 

 reddish bars ; if these were hens, then of the nine young koels whose early 

 history I followed no fewer than six, or two-thirds of the whole, were hens. 

 If, however, these birds were cocks, then four of the nine were hens and five 

 cocks, a gain, as we have seen, one of the koels in nest VI had white bars and 

 the other reddish ones. I have already givt n reasons for thinking that both 

 eggs were laid by the fame hen, and it seems unlikely that these should give 

 rise to two females each differing markedly from the other in appearance. 



The next point which these experiments bring out is the easiness of the 

 path of the cuckoo. A nesting bird seems to cast intelligence to the winds. 

 The crows sat upon a fowl's egg, upon a sea-green paddy-bird's egg, and on a 

 golf ball, apparently without noticing that these differed in any way from their 

 own eggs. Again, the addition or subtraction of an egg or two was not noticed. 

 Further, when I introduced a young koel into a nest containing eggs only, the 

 parent crows at once set to work to feed the young koel, as though they were 

 quite accustomed to young birds, being thus introduced into the nest ! 



I consider it proven that the koel undoubtedly destroys or tries to destroy 

 some of the crow's eggs it finds in the nest. My idea is that, given the 

 opportunity, the koel wiil destroy all the crow's eggs. Unfortunately there 

 was so much tampering with the nests that came under my observation that 

 the evidence on this point, and indeed on most points, is not so conclusive as 1 

 could wish. However, I have no reason to think that nest number "VI was 

 tampered with by human beings, yet all the crow's eggs disappeared. Then 

 there is the nest we found containing only two koel's eggs which were nearly 

 incubated. Lastly, there was the incident of the broken crow's egg on the 

 tn-ound under nest number X. 



