Now they must hurry or the wrens will come and drive them out of house and home. One of the bluebirds remains in the nesting-place, or very near it; for if the house be empty of inmates, the wrens make quick work of pulling out such straws and nesting material as have been gathered. If the people of the farm or other home be on the watch they can lend a hand at this time. Offered inducements by way of many boxes or nesting-places, with handfuls of fine litter, will attract the wrens, and the bluebirds will be untroubled. It may be that a cold snap will come up in a driving hurry after the nesting is well under way. In this event the birds will disappear, probably to the deep, warm woods, or the shelter of hollow trees, until the storm be past, when they will come again and take up the work where they left off. This sudden going and coming on account of the weather has always been a mystery to those who study the bluebirds. Some imagine they have a castle somewhere in the thickest of the woods, where they hide, making meals on insects that love old, damp trees. Caves and rock chambers have been explored in search of the winter bluebirds, but not a bird was found in either place. They keep their own secrets, whether they fly far off to a warmer spot, or whether they hide in cell or castle. If the work is not anticipated by human friends, and the nesting-places cleaned out in advance of the birds, they will tidy up the boxes themselves, both birds working at it. What do they want of last year's litter with its invisible little mites and things that wait for a genial warmth to hatch out? House-cleaning is a necessity with the bluebirds. When the nest is done it is neat and compact, composed of sticks and straws with a softer lining. The birds accept what is ready to hand, making no long search for material. Being neighbor to man and our habitations, it uses stable litter. The three to six pale blue eggs contrast but slightly with the mother's breast. The little ones grow in a hurry, for well it is known that more broods must be attended to before summer is over. Sometimes the nest is placed at the bottom of a box or passageway, and the young birds have difficulty in making their way to freedom. The old birds in such a case are said to pile sticks up to the door, and the little ones walk up and out as if on a ladder! The mother soon takes to preparing for another brood, and the father assumes all the care of the young just out, leading them a short distance from the mother, and teaching them to hunt insects and berries. The little ones are not blue, as any one may see, but brown with speckled breasts. These speckled breasts of young birds are fashionable costumes for many other than bluebirds. They remind one of infantile bibs, to be discarded as soon as the young things eat and behave like their elders.