OTES 



PAEENT -BIRDS REMOVING MATTER FROM 

 THE GAPES OF NESTLINGS. 



For some j^ears now I have been x^aying particular atten-' 

 tion to the nestlings of common birds. It is of course now 

 known to all ornithologists that the parents keep the nest 

 clean (as a general rule) by carrying awaj^ the excrement, 

 and often by swallowing it, during the early part of the 

 nestling-period. 



While watching these operations I noticed that, after 

 feeding the young, the old birds almost always examined 

 the gapes of the nestlings and often removed something 

 from them. It was not at all easy to come to a conclusion 

 as to what was removed, for it was usually impossible to 

 obtain an}i:hing for examination, especially as most of 

 the parent-birds s\^-allowed what they removed. I feel 

 convinced, however, that what is removed is either food 

 which the nestling has not swallowed, or it is undigested 

 matter that has returned to the gape. In the case of some 

 of the warblers (Greater and Lesser A^Tiitethroat, Blackcap, 

 and Willow- Warbler especially) I have noticed that the matter 

 removed often has the appearance of a caterpillar-skin, and 

 I feel certain that the skins of caterpillars cannot be digested 

 by the nestlings and are disposed of in this way. Dr. Wills 

 and Mr. R. Iremonger both watched a Lesser TOiitethroat's 

 nest with me, and also considered that this was the case. 



I have also seen matter removed from the gape of nestling 

 Cuckoos. Generally this was shallowed but once I saw it 

 dropped by a Common AMiitethroat. I was in a "hide " at 

 the time and was afterwards unfortunately unable to find 

 what the bird had for it fell into some rather tall after- 

 math. So far as I could see it had the appearance of wings 

 of various flies. Mr. H. Armj^tage Sanders, when photo- 

 graphing a Cuckoo-nestling eight days old, saw the Hedge- 

 Sparrow foster-parent remove a white " blob " from the 

 Cuckoo's mouth and swallow it. This, I think, must have 

 been a caterpillar- skin. At the time the Hedge-Sparrows 

 also carried away the excrement of the young Cuckoo, for 

 we saw it done several times. I have also examined a Cuckoo 

 immediately after it was fed, and found no trace of food 

 in the gape. I then waited until I saw the Hedge-Sparrow 

 foster-parent approaching with food, and before it reached 



