Foraging dynamics in Stellerʹs jays: size and viability of cacheable food items

Several species of birds and mammals cache food items, which in harsh conditions may translate into improved survival or reproductive success. Animals may benefit from evaluating the quality of cache items in terms of size, nutrition and storage viability. Stellerʹs jays, Cyanocitta stelleri, which cache seeds for later consumption, may handle multiple food items with their beak prior to making a selection. By picking items up, individuals may use visual and tactile cues to evaluate size and shell condition. The number of items an individual jay handles is repeatable, reflecting consistent individual-specific foraging behaviours that may differentiate success at selecting high-quality cache items. In this study we quantified population-level preferences for food items based on size and shell integrity, and individual Stellerʹs jay sampling behaviour when presented with these choices. Using field trials with free-ranging subjects, we quantified sampling frequency in a variety of choice tests and measured individualsʹ success at choosing higher-quality items. We found that Stellerʹs jays selected items of greater weight and items with intact shells, and preferences for these properties were of comparable magnitude. Jays sampled more nuts during choice sets involving cracked and intact shells, resulting in individuals selecting more profitable nuts for caching. These results may suggest that Stellerʹs jays evaluate cache items based on both current and future expected energetic values, and that sampling behaviour may enable them to choose more valuable forage items.