THE AUKS 283 



single fish which is usually slightly longer than the bill and is held 

 parallel to the bill, with the tail hanging from its tip. This fish may be 

 almost as long as the chick itself; but this formidable meal will be 

 swallowed by the chick, always head-first, and digestion begins with 

 the head, although the tail of the fish may not visibly disappear from 

 the mouth of the nestling for some time. Often after returning from 

 the sea with a single large fish the adult will hold it for a long time, as 

 during courtship, as it sits semi-upright upon the ledge. Why it should 

 do this is not quite clear, but it may be that unless the chick importunes 

 sufficiently the feeding reaction in the adult is not released. The adult 

 may even fly away from the ledge, still carrying the fish, only to 

 return later with it. If all the chicks near the alighting bird have 

 been fed recently, there would, of course, be a wastage if the adult 

 dropped the unwanted fish at random on the ledge. This does happen, 

 though rarely, and if the chick is well grown, vigorous and hungry 

 enough, it will pick up the fish then, or later. But usually the adult 

 retains the fish until one or other of the chicks of the colony starts 

 calling and pecking to be fed. Since both sexes in the adult are alike 

 and the chicks themselves cannot be distinguished one from the other 

 (unless they vary much in age) , it has not been easy to prove that com- 

 munal feeding exists; but hungry chicks will be seen making their 

 way past satisfied chicks and brooding adults, to reach an adult 

 holding fish. Also chicks have been seen to wander from one adult to 

 another, and even to a third, and were brooded by each in turn 

 (Lockley, i934d). There seems no doubt that a chick will be adopted 

 as easily as an egg may be pirated, even if the adoption of the chick 

 is a matter of only a short period during the absence of the legitimate 

 parent. There also seems little doubt but that there is voice recognition 

 in this species; a chick which feels cold and temporarily has no 

 adult to brood it will squeak until its wants are satisfied by the nearest 

 willing adult. Yet these squeaks seem to cause more agitation to one 

 particular adult than the rest (and this the observer presumes to be 

 one of its parents), which may make its way towards the chick, calling, 

 or call the chick to its side to be brooded or fed, or both. Promiscuous 

 or communal feeding of young birds is not unique to the guillemot; 

 it occurs regularly among other sociable species, notably the penguins, 

 and has occurred spasmodically with passerine birds. Of mammals 

 the female bat is said to feed the first young one which reaches her on 

 her return to the crowded communal nursery-roosts (Casteret, 1947). 

 Little auks feed their chick on crustaceans and plankton, which they 



