84 U.S. NATIONAL MUSEUM BULLETIN 26 5 



of this method of egg deposition the argument that such a nest cannot 

 even "bear the weight of the young Cuckoo when half grown and often 

 breaks down before it is half fledged. ... It is equally certain that 

 the Cuckoo cannot enter so small a nest. It is a very strange sight 

 when a young Cuckoo gets too large for its abode. At first the nest 

 itself expands and the young bird sits with its head out of the entrance 

 encased in a trellis-work of grass, etc., which gradually gets thinner 

 and thinner until it bursts and the cuckoo is thrown headlong to the 

 ground . . . ." Even if, as Baker suggests, the catapulted young 

 parasite is then fed on the ground by its foster-parents, it would 

 seem that in many instances the destruction of the nest would be 

 fatal to the nestling in it or that an altricial young prior to the fledging 

 stage would not survive long either out of, or deprived of the protection 

 of, the nest. 



While mandibular egg deposition may thus seem to have slight 

 evolutionary value, nevertheless, that occasionally brood parasites do 

 resort to this behavior pattern is of interest since it evidences a degree 

 of psychobiological adaptiveness that is in itself quite remarkable. 

 This, in turn, makes one wonder if the habit may have started early 

 in cuculine history with more ordinary, less flimsy or inseciu-e, or less 

 uncomfortably small types of host nests. It is conceivable that it 

 might have had a value, both immediate and in the long range of 

 natiu-al selection, of being a more rapid method of egg deposition than 

 du*ect laying into the nest; it certainly coiJd have been advantageous 

 to the parasite, especially in nests well guarded by their owners. Once 

 such a habit, or such an extension of it, had become part of the scope 

 of the innate behavior of the cuckoos, it could reappear from time to 

 time. 



The glossy cuckoos usually lay but one egg in any one nest. WhUe 

 there are records of two and even of tlu"ee eggs of some of these cuckoos 

 in a single host nest, they are definitely exceptional. As is weU docu- 

 mented, multiple eggs deposited in the same nest are extremely rare 

 in the Em^opean cuckoo, Cuculus canorus, but are quite frequent, in 

 fact usual, in some of the crested cuckoos of the genus Clamator. The 

 species of Chrysococcyx agree much more with Cuculus than with 

 Clamator in this aspect of their parasitism. The rarity of multiple 

 versus single eggs in individual nests is true of all the glossy cuckoos 

 of whose eggs enough is known. While the following figures relate 

 particularly to some of the African species on which I have more 

 extensive data, the pictiu-e is similar in the Australasian members of 

 the genus. In C. caprius my records show 231 host nests \dth a single 

 didric cuckoo egg in each, 12 nests with two each, and only 2 nests 

 holding three of the parasitic eggs apiece. In other words, out of a 

 total of 261 didric cuckoo eggs, 245 were "singles" when laid, and 16 



