Symbolic Communication Between Two Pigeons, (Columba livia domestica)

Science. 1980 Feb 1;207(4430):543-5. doi: 10.1126/science.207.4430.543.

Abstract

Through the use of learned symbols, a pigeon accurately communicated information about hidden colors to another pigeon. Each verbal exchange was initiated with a spontaneous request for information. The two pigeons engaged in a sustained and natural conversation without human intervention.