We present evidence for binocular summation in pigeons in a choice reaction time paradigm. Considering binocular vision as the result of a race between the equivalent eyes, pigeons can adopt both a 'subject by subject' and a 'trial by trial' race model, and binocular advantage can be attributed merely to a probability summation. Pigeons were tested on a visual discrimination task in which the time for detection was gradually reduced and a quick response was required. The time presentation of a small black spot could vary from 2000 ms to the shortest value (157-226 ms) allowing maintenance of a satisfactory performance criterion.