DIPPER. 237 



down, its body oblique, it holds itself down by muscular exer- 

 tion, its course beneath the surface often revealed by a line of 

 rising bubbles. In this way it secures its food, the larvae of 

 aquatic insects, including the encased caddis worms, beetles, 

 Limnea^ Ancylns and other fresh-water molluscs. A favourite 

 food is the small crustacean Gammariis — the "water-flea" — one 

 of the worst foes of trout-ova ; there is no direct evidence 

 that the bird eats ova, though it has been known to occasionally 

 catch fry, and it may therefore be classed as useful rather than 

 harmful on a trout-stream. On the banks and rocks it walks 

 and runs, seeking terrestrial insects. More rarely it swims, 

 floating hghtly. 



The winter habits of the Water-Crow, CoUey or Bobby, as it 

 is called indifferent districts, vary considerably and apparently 

 individually. When the swift hill-becks are frozen it is forced 

 to descend to the lowlands and even visit the coasts, but some 

 will remain if thei-e is any open water. Yet in mild winters I 

 have found upland haunts almost deserted, and at this season 

 numbers appear on the lower stretches of the rivers. The sweet, 

 hurried. Wren-like lyric of the Dipper, mingling with the sound 

 of tumbling waters, may be heard at any season, but mostly 

 from December until May. During courtship the cock sings 

 whilst he runs and postures before the hen, exhibiting his snowy 

 breast, and when displaying he will take long and high flights, 

 like those of the Kingfisher, accompanied by sharp metalHc 

 calls — clink, clink^ differing from the normal zit. 



The nest is by the water, often under it — on the rocks 

 beneath a fall ; it is large, globular or oval, like a massive 

 Wren's nest, built into some crack or hollow in the rock, in the 

 masonry, or on the supports of a bridge, or, more rarely, in an 

 overhanging branch. It is composed of green moss when the 

 water splashes or actually flows over it, but on dry grey rocks 

 often of dead grass and leaves. This ball, however, is merely the 

 shelter or envelope ; below the median line, usually hidden beneath 



