National Geographic : 1944 Jun
A Bag of Bird Portraits () National Geographic Society Kodachrome by Arthur A. Allt, Why the Two-story House? To Oust a Social Parasite A Cowbird laid an egg in this Yellow Warbler's nest beside one of the owner's. Refusing to be imposed upon, the Warbler added another nest, burying the Cowbird's speckled contribution where it could not hatch. The Warbler then laid eggs in the second-floor nursery and here busily cares for triplets.