Vol. VI. 

 igo7 



j Campbell, Observations on the Rearing of a Cuckoo. 125 



phases of the Cuckoo's economy, as well as in that of all birds, 

 cannot but add greatly to the charm of nature study to-day. 



{e.) That the Cuckoo's egg hatches first, and the j^oung is at 

 first of a somewhat similar appearence to the proper expected 

 nestlings. The advantage of this is obvious. Whether the 

 strange egg is laid first, or really takes less time (as by 24 hours 

 in the above case) to hatch, is not quite proven. I am inclined 

 to the latter opinion, for two reasons. Firstly, among Passerine 

 birds, without exception, the parent does not sit until the full 

 clutch is laid. Secondly, because there are numerous instances 

 of deserted birds' nests being found with a single Cuckoo's egg 

 therein, indicating that the unwonted appearance of the deadhead 

 before the nest-owners had laid any eggs themselves was a sure 

 sign of trickery. The White-eared Honey-eater {Ptilotis 

 lencotis), of an ingenious turn of mind, has been known to build 

 a second bottom to its nest to cover up the unwelcome &gg of a 

 Pallid Cuckoo. Here again the selective workings of nature for 

 the protection and reproduction of the Cuckoo are evident. 

 The eggs deposited too early by over-anxious Cuckoos are 

 deserted, and only those placed so as to avoid suspicion hatch 

 to continue the race. I believe that a Cuckoo's ^gg is usually 

 placed in a nest when one of the foster-bird's eggs has been laid. 

 The foster-bird, somewhat puzzled no doubt, about the un- 

 expected arrival, then lays one other &^g to complete the 

 number — three — which is its usual clutch. For in most 

 instances where a Cuckoo's Q.gg is taken from a nest the clutch 

 of the rightful owner is not complete in itself. The taking of a 

 full clutch with a Cuckoo's ^gg is, I fancy, an exception. 



A difficulty now suggests itself. Admitting the persistent 

 and relentless " law of natural selection " for the increase of the 

 Cuckoo, what will become of some species of birds which largely 

 play the part of foster-parents } Surely extinction awaits them, 

 and the Cuckoo will then coolly devote all its attention to its 

 other nurses (for no known Cuckoo confines itself exclusively to 

 one species as foster-parent), deliberately effacing them in turn. 

 Its hands in this dire work are strengthened, so to speak, by the 

 fact that the Cuckoo's numbers are increasing annually in pro- 

 portion to those of foster-parents, for every Cuckoo reared 

 means two, perhaps three, less host birds. My note book helps 

 me in line with these statements. In a restricted mountain 

 gully, in 1895, I discovered nine nests of Petrceca rosea in one 

 day, most of them containing young Robins. Visiting the locality 

 several times in 1901, I was able to take three eggs of the 

 Cuckoo {C. variolosus), all from Robins' nests, and I also dis- 

 covered two young Cuckoos being fed by their tiny foster- 

 parents. During last season, though I admit I had not the 

 opportunity of hunting as carefully as hitherto, I did not find a 



