subjects were 12 experimentally naive White Carneaux pigeons purchased from the Plametto Pigeon Plant , Sumter , SC. the pigeons were maintained at 75-80% of their free-feeding weights with Puirna Pro Grains, mostly provided during experimental sessions. the pigeons wer housed in individual wire mesh cages with water and grit freely available. The colony was maintained under a 12-hr/12-hr light/dark cycle