The woodpecker trusts no living species save his own, and drills high up into a hollow tree-trunk for his home. The cactus wren and crissal thrasher build in the geographical centres of tree choyas, so protected by 500,000 spines that no hawk or owl can reach them. This catalogue could be extended to a great length; but why pile evidence upon evidence! It cannot be correct to assume that the nesting activities of birds are based upon instinct alone. That theory would be untenable. New conditions call for independent thought, and originality of treatment. If the ancestral plans and specifications could not be varied, then every bird would have to build a nest just "such as mother used to make," or have no brood. All bird students know full well how easily the robin, the wren, the hawk and the owl change locations and materials to meet new and strange conditions. A robin has been known to build on the running-board of a switch-engine in a freight yard, and another robin built on the frame of the iron gate of an elephant yard. A wren will build in a tin can, a piece of drain tile, a lantern, a bird house or a coat pocket, just as blithely as its grandmother built in a grape arbor over a kitchen door. All this is the hall mark of New Thought. Whenever children go afield in bird country, they are constantly on the alert for fresh discoveries and surprises in bird architecture. Interest in the nest-building ingenuity and mechanical skill of birds is perpetual. The variety is almost endless. Dull indeed is the mind to which a cunningly contrived nest does not appeal. Tell the boys that it is _all right_ to collect _abandoned_ nests, but the taking of eggs and occupied nests is unlawful and wicked. The Play-House of the Bower Bird. Years ago we read of the wonderful playhouses constructed by the bower birds of Australia and New Guinea, but nothing ever brought home to us this remarkable manifestation of bird thought so closely as did the sight of our own satin bower bird busily at work on his own bower. He was quartered in the great indoor flying cage of our largest bird house, and supplied with hard grass stems of the right sort for bower-making. With those materials, scattered over the sand floor, the bird built his bower by taking each stem in his beak, holding it very firmly and then with a strong sidewise and downward thrust slicking it upright in the sand, to stand and to point "just exactly so." The finished bower was a Gothic tunnel with walls of grass stems, about eighteen inches long and a foot high. In making it the male bird wrought as busily as a child building a playhouse of blocks. Our bird would pick up pieces of blue yarn that had been placed in his cage to test his color sense, but never red,-- which color seemed to displease him. As the bird worked quietly yet diligently, one could not help longing to know what thoughts were at work in that busy little brain.