Caching and Recovery in Scrub Jays: Transfer of Sun-Compass Directions from Shaded to Sunny Areas

Abstract

Current models of navigation and homing (e.g., Wallraff 1974, Wiltschko and Wiltschko 1987) assume that compass orientation not only guides the birds on their homeward flight but is also used to build a navigational map. This is taken to be directionally oriented mental picture of the spatial distribution of navigational factors. Recent findings of Wiltschko and Balda (1989) indicate that compass orientation is also of major importance in foraging. For example, Scrub Jays, Aphelocoma coerulescens, were observed in an octagonal outdoor aviary when caching and recovering their seeds. When their internal clock was shifted 6 hr between caching and recovery, they altered the sectors of their search by the predicted 900 thus showing that they used the sun compass. This suggests that birds might generally have a directionally oriented view of space that is used for a wide variety of tasks. In our earlier experiments (Wiltschko and Balda 1989), caching as well as recovering took place in sunshine. Although the Scrub Jays live in a relatively dry, open environment, they may have opportunities to cache in the shade and recover in the sun or vice versa-the distribution of shaded and sunny areas could be quite different at the times of revisiting cache sites. This raises the question whether a jay can remember a cache site relative to a sun compass direction when it was unable to see the sun directly while caching. Is it possible that a bird includes a site in its sun compass oriented spatial map that it has never seen in sunshine? Here we report the first results of an attempt to answer this question.