And when we travel far off to Australia, we find ground birds which do not even sit on their eggs, nor take care of their young, but leave them as reptiles do to be hatched in the sun. The Brush-turkeys and Megapodes of Australia and the islands near, and the Maleos of Celebes--all of them scratching birds--come out of the thick jungle and lay their brick-red or pale-coloured eggs on the shore, never taking any more notice of them. The maleos simply scratch a hole in the sand and bury the eggs, the brush turkeys and megapodes[100] scratch together all kinds of rubbish and dead leaves, carrying them in their long curved claws, and adding them to the heap till they have made a mound sometimes more than seven or eight feet high, and twenty feet across at the base; an astounding size, when we consider that the brush turkeys are not nearly as large as a good-sized turkey, and the megapodes not larger than hens. It is to these mounds that the mothers come about every ten days, and lay an egg _upright_, till each has laid eight or nine, and then she comes no more; but after many weeks the little chicks work their way out fully fledged, and fly away to get their own living. The probable reason, Mr. Wallace tells us, for this curious habit of mound-building, is that the eggs are so large that the mother can only lay one every ten days, so that if she sat upon them she would be worn out with fatigue and want of proper food before they were all laid and hatched. * * * * * We see then that the scratching birds live nearly all over the world, yet, no doubt, it is a disadvantage to them that in their ground life they have become so heavy that they cannot fly so lightly or so far as their near allies, the pigeons, which, like them, feed on the ground. For the Pigeons have already made many steps forward in life. Their wings are strong, so that they can fly for great distances; their toes are slender and well fitted for perching; and though it is true that our tame pigeons and the wild rock-pigeons from which they are descended do not build nests, but lay their eggs in dovecots or church towers, or, if they are wild, in holes in the rocks, yet the beautiful blue-gray wood-pigeon, with her pure white collar and soft cooing note, builds a nest in the trees-- “The stock-dove builds her nest Where the wild flowers’ odours float;” though it is but a rough one, made, as well as her weak feet and bill can do it, of a few stout twigs, laid so loosely that her two little white eggs may be seen from below, and even sometimes fall through. [Illustration: Fig. 42. Wood-pigeon on her nest.]