312 THE DIPPER 



serves to make them more visible, in the darkness, to the bird as it 

 enters, and so lessens the danger of their being trodden upon and 

 broken. 1 It still remains to be shown, however, that species, 

 e.g. the tits and daws, which, owing probably to some change in 

 their nesting habits, lay coloured eggs in holes, suffer appreciably 

 on that account. Is there, in the case of these species, a process 

 of natural selection actually going on which tends to eliminate by 

 breakage the more thickly spotted and darker eggs in favour of less 

 spotted and paler ? The question is one that careful records would 

 answer. 



After about two weeks from the date of laying, the eggs hatch out, 

 and the shells are removed by the parents and dropped at a distance. 

 From this moment both parents are assiduous in feeding the young, 

 one, according to my observation, generally foraging up-stream, the 

 other down. For many hours I watched a pair thus engaged near 

 Inversnaid, by Loch Lomond. Each would return at intervals, alight 

 on a boulder beneath the nest, curtsy with a droop of the wing and a 

 downward flick of the tail, dart up to the nest, disappear into it, come 

 out followed by fervent pteep ! pteeps ! from the throats of two lusty 

 young, alight on the rock, curtsy, step daintily to the water, wash its 

 beak, splashing it from side to side, and fly off with the familiar chit ! 

 chit ! 



That the dipper should so far have departed from Passerine cus- 

 toms as to wash its bill in the water instead of wiping it on a branch 

 or rock is noteworthy. The fact that the young uttered their cry after 

 and not before receiving the food is also curious, for while the food was 

 being pushed down the deep yellow throat of one, the other had ample 

 time to manifest its feelings. It may, of course, have been overcome 

 by them ! 



The young in question showed the feathers just sprouting, and 

 were therefore not big enough to thrust their heads out through the 

 entrance, as they do later, and so watch for and greet the arrival of 



1 W. P. Pycraft, A History of Birds, p. 207. 



