12 



THE ZOOLOGIST. 



shows that the Dunlins miss more than they find. The tap- 

 pings and septate probings may occur singly or in lines of two 

 or three each, and may or may not end in a deep probing. Deep 

 probings may be found together or singly at wide intervals, with 

 or without associated septate probings. The number of con- 

 tiguous tappings and septate probings may be great. I once 

 counted forty in line, gradually deepening to end in a complete 

 probing, and on another occasion forty-seven, when no deep 

 probing was present. This was on a small patch of half-dried 

 mud overlying coarse gravel, and when the mud was sifted 

 nothing was found. The contiguous lines of probings may be 

 straight or curved, directed forwards or to one side, and a fairly 

 common form is a circle of ten to twenty tappings and septate 

 probings, ending in a complete probing near the first tapping. 

 As a general rule, ten to a hundred imprints are found on the 

 square foot, of which rather less than half are deep probings, 

 but the ratio may be as high as one in three hundred, or even 

 one in five hundred. To produce a tapping the mandibles are 

 required to be separated one millimetre at the tip, to produce a 

 septate probing two or three millimetres. The length of a 

 septate probing is five to six millimetres, which is considerably 

 shorter than the seven or eight millimetres of a double probing 

 made experimentally with a closed bill, and the ten to thirteen 

 millimetres of the double complete probing occurring in nature. 

 The deep probing is directed slightly forwards, is cylindrical in 

 the upper part, and expanded towards the end into a semi- 

 bulbous form, the concavity being on the front aspect of the 

 probing, a relation which can be learned by comparing the 

 probing with the corresponding footmarks. 



That the mandibles are separated in the act of tapping and 

 probing runs contrary to accepted opinion ; while the con- 

 struction of the bill, with its guarded tip, points to its use with 

 the mandibles closed. Direct observation of so small a detail is 

 not easy on account of the Dunlin's rapid movements, but it 

 can be made when the bird comes between the observer and still 

 water which is reflecting the light of a white cloud. I have 

 chanced on these ideal conditions twice. On the first occasion 

 during rapid probing the mandibles were separated all the 

 time. The degree of separation varied a little, and at times 



