A comparison of four corvid species in a working and reference memory task using a radial maze.

Birds were tested in an open-room radial maze with learned spatial locations that varied from trial to trial (working memory) and locations that remained spatially stable (reference memory). Three of the species, the Clark's nutcracker (Nucifraga columbiana), pinyon jay (Gymnorhinus cyanocephalus), and Western scrub jay (Aphelocoma coerulescens) store food to varying degrees. The other species, the Eurasian jackdaw (Corvus monedula) does not. Pinyon jays and scrub jays performed better than the nutcrackers and jackdaws in both working and reference memory components of the maze. The pinyon jay and jackdaw performed as would be expected on the basis of their natural history and previous research, but the scrub jay and nutcracker did not. Results are consistent with phylogenetic relationships among the 4 species, but could also be explained by differences in response strategies or interference in processing both types of memory components of the maze.