262 FRANCIS H. HERRICK 



mud is essentially lacking in a finished nest, a deep foundation 

 and thick wall of dead grass and stubble is commonly found. 

 All that we can say at present is that while mud is regularly 

 used in a peculiar w^ay and with a definite result, it is some- 

 times wanting, the only earth present being that which inci- 

 dentally clings to the roots of stubble pulled from the ground. 



I have a robin's nest taken from the spruce woods on Great 

 Duck Island, Maine, which is composed wholly of coarse spruce 

 twigs, black peat, and a lining of withered grass blades, mater- 

 ials which w^ere available in the immediate vicinity of the nest. 

 It is the only specimen which I have seen built so largely of 

 coarse stiff twigs, but the dimensions of the inner wall, and the 

 treatment which the material received are typical. The varia- 

 tion was evidently a response to the immediate environment, 

 and is unimportant. Nuttall speaks of a nest of this bird, 

 "bottomed " with a mass of pine shavings taken from a car- 

 penter's bench, a variation similar to that mentioned above. 

 Again if given strings or streamers of colored yarn, though 

 white is preferred, robing often take them eagerly and work 

 them more or less effectively into their nests. I have even seen 

 a pocket handkerchief which a robin picked from a line or from 

 the ground and carried into a tree, where, however, it was 

 caught so that the bird failed to use it. 



The fact that the robin brings plastic earth to its nest in two 

 ways, incidentally in the damp soil clinging to the roots of 

 pulled grass or stubble, and directly in large lumps of barely 

 consistent mud, and that all is treated in a fairly definite manner 

 to mold a symmetrical cup is a highly interesting fact, for it sug- 

 gests the origin of the direct use of mud in all such building 

 operations. A more durable and better nest resulting from the 

 casual use of plastic earth thus accidentally introduced at an 

 early stage of the proceedings may have furnished, on the prin- 

 ciple of selection and other possible factors of evolution, the 

 starting point for what in the course of ages became a fixed 

 and settled custom. ^^ The fact also that its near ally, the black- 

 bird of Europe {Merula atra), builds in precisely the same style, 

 not only suggests the high antiquity of the practise, but illus- 



■" It should be added that in exposed situations and when subject to drenching 

 rains the mud cup is distinctly disadvantageous, since without drainage below, 

 the nest is liable to catch and hold too much water. 



