the Coloration of Eggs. 545 



rat and weasel/^ The case is not a good one, as the obser- 

 vations on the Little Bittern were carried out in a locality 

 in which rats were not actually noted, though snakes were 

 abundant ("seven asleep on one raft of reeds "), but it is 

 useful as indicating a line of observation which may give 

 intei-esting results. 



He further suggests problems that, as he rightly insists, 

 are probably explicable only in relation to a number of 

 interacting factors, of which, however, varying degrees of 

 unpleasantness in the egg might well be one — problems of 

 distribution and relative success. Also, he rightly attaches 

 much importance to the great principle of compensation, and 

 naturally at once sees what a straightener-out of our diffi- 

 culties the acceptance of nauseousness as the hitherto 

 missing counteragent to conspicuousness in eggs would 

 prove to be. He expects the eggs of the Nightjar and the 

 Stone-Curlew " to be fairly edible," being protected by 

 their own coloration and that of their parents, but thinks 

 it likely that the egg of the Song-Thrush, a bird "not so 

 pugnacious as a Blackbird and mucli less so than a Mistle- 

 Thrush, and far less than the Fieldfare at the nest," will be 

 *"' refused by birds and animals which would take the egg 

 of Blackbird and Mistle-Thrush.'''' And he mentions a 

 great Italian marsh on which the Water-Rail (covered 

 nest) and Baillon's Crake (open nest, " or rather tiny pad," 

 and protectively coloured egg) were found breeding success- 

 fully. But what of the Little Bittern, with a white e^^ and 

 open nest, yet '' abundant " there and " enjoying a large 

 measure of immunity "? The Bittern's sharp bill occurs to 

 one, yet cases could be given in which there is no such 

 escape as this from the conclusion that there is a missing 

 counteragent. 



I would suggest, finally, that the common habit possessed 

 by birds of removing or deserting eggs or young that have 

 been visited is surely essentially connected with the possi- 

 bility of deferred attack by an enemy that was not hungry 

 enough for them on first discovery. 



SER. X. VOL. IV. 2 P 



