A study of cues used by large-billed crow in picture recognition

Abstract

There has been much research into the ability of large-billed crows (Corvus macrorynchos) to recognize pictures, but little is known about what cues in a picture they use for recognition. We trained four adult crows to select pictures of specific species of bird, and we examined the effects of picture modification on their selections. Two of them were trained to select pictures of sparrow from other species of birds in a two-alternative forced choice test; the other two were trained to select pictures of pigeon. After selecting the 'correct' bird, they were tasked to select novel and modified pictures. We found that the crows' discrimination was greatly affected by the color of the image, but that they could not select the correct image only from its colors; they also used features such as shapes and patterns to select the correct image. In addition, we found that the cues used to recognize the pictures may have differed between individuals.