The song thrush of Europe is perhaps a borderline case. It feeds in part on snails. To get the soft edible animal out of its shell, it carries or drags the snail to a favorite rock, its anvil, and there hits it against the anvil until the shell is broken and its contents exposed. The question is, can this be considered as using a tool? If the song thrush moved or prepared the rock, which it does not do, there would be no question that it was a tool. The sea otter brings a stone from the bottom of the ocean and places it on its floating body to use as a similar anvil in cracking hard objects, and this undoubtedly is the use of a tool. At the other extreme are many species of birds that beat their prey on branch or ground, wherever they happen to be. The song thrush is certainly an advance over that, and can, I think, be considered as using a tool in a primitive way. A few other species, too, bring shellfish to special places. Gulls on our coasts pick up mussels and clams and, flying over a rock or some other hard surface, drop the shellfish, and follow it down. If the shell is broken, the dish is ready for the gull; if the shell is not broken the gull takes the shellfish up to a higher altitude and tries again. In places where hard-surfaced roads are conveniently located gulls have learned to use them as shell-breaking places, and such roads become littered with shells. Crows of more than one species also use the same routine in breaking open shellfish, and they, too, have learned to use special hard surfaces, such as masonry walls, on which to drop the shellfish. PAINTING A BOWER The satin bowerbird of Australia, a species known to science as _Ptilonorhynchus violaceus_, has also been considered as a case in point when discussing the use of tools. The birds are somewhat larger than a robin, the male glossy blue-black, the female greenish. The male of this species constructs an elaborate bower, presumably for courtship purposes. It makes it of sticks and twigs, and decorates it with bright and curious objects such as shells, feathers, bits of bone, and fruits, as do several other species of bowerbirds. But the satin bowerbird is unique in painting the inside of its bower. Fruit is crushed in its bill, and the bird, using its bill as the tool or paintbrush, smears the fruit juice on the sticks on the inside of the bower. While this is a wonderfully strange habit, and apparently unique in the bird world, it is doubtful if this behavior can be considered as using a tool. If the satin bowerbird used a twig, or a wad of moss or fiber, which it does not do, in spreading the paint, the case would be clear.