Size does not matter, but features do: Clark's nutcrackers (Nucifraga columbiana) weigh features more heavily than geometry in large and small enclosures

Two groups of Clark's nutcrackers (Nucifraga columbiana) were trained to locate a hidden goal which was consistently located at one corner of a fully enclosed rectangular environment with distinctive cues available at each corner. One group was trained in a small enclosure, whereas the second group was trained in a large enclosure. Once the birds were showing accurate search behavior, they were presented with non-reinforced tests in either the same sized environment as training or the novel sized environment, as well as in a square-shaped environment. The birds were able to accurately search at the two geometrically correct corners when the four distinctive features were removed showing that they had encoded geometry. Although accuracy was greater when tested in the same sized environment as during training, accuracy was above chance in both environments. Regardless of the size of training enclosure both groups showed primary control by features along with secondary control by geometry. Furthermore, when the features and geometric cues provided conflicting information as to the goal location, both groups weighed featural cues over geometry, and this was independent of whether the size of the testing environment was maintained or manipulated. These results show that for Clark's nutcrackers the size of the environment had little effect on the weighing of featural and geometric cues. Furthermore, although nutcrackers encoded both features and geometry, when spatial cues provided discrepant information as to the goal location, nutcrackers relied primarily on features. This article is part of a Special Issue entitled: CO3 2013.