nOTES 



THE FLANGES AND MOUTH-SPOTS OF NESTLINGS. 



I HAVE read the article on " Nestlings " with interest, and if I 

 may be allowed to express the wish, it is that circumstances 

 had permitted Mr. Pycraft to deal with the subject more 

 fully. 



It is probable that the hps or flanges have another use 

 beside that of serving to outhne the mouth by their generally 

 paler colour. When the nestling opens its mouth widely, 

 the flanges straighten out like the sides of a leather purse, 

 and, becoming stretched, fill up much of the lateral gaps 

 between the separated mandibles, and as these apparently 

 bend over into a nearly horizontal position, the mouth is 

 converted into a funnel-shaped cavity, \\'ith an everted and 

 almost level rim. To drop food into a chick's moutli is not 

 an easy matter, as the scarcely-developed muscles are unable 

 to support the head steadily for long, and it usually jerks to 

 and fro in a provoking way. Thus the flanges may prevent 

 the escape of food side\^ays from the mouth, and according 

 to my limited experience, they attain the greatest develop- 

 ment in the nestlings of those species which nest commonly 

 in dark situations, and which may be sujiposed to have 

 difficulty in feeding their young. 



With regard to the spots in the mouths of certain cliicks, 

 there can be little doubt that the spots are a distinct aid to 

 the economy of those nestlings which possess them. During 

 the past summer I tested a number of yoang Skylarks, less 

 than six days old, with a view to finding out A\'hich part of the 

 mouth was most sensitive to stimulation. The inside of the 

 mouth is yellow. A black spot is present on the tip of the 

 tongue, and another on tlie inside of the tip of the lower 

 mandible. I used small worms and slugs, similar to those with 

 which the parents fed the young, and placed them on different 

 parts of the gaping mouths. 



The experiments were haphazard, if you like, as I hesitated 

 from a touch of sentiment, perhaps, to deprive the nestlings 

 of their mother's warmth for too long, knowing well their 

 liability to lung trouble, and further experiment may modify 

 the results set down below. The flanges were found to excite 

 no response. The chicks continued to gape, as if nothing 

 had been supplied to them, and when they, ^\'earied by their 

 efforts, sank down into the nest and closed their mouths, the 



