Both the past and the present affect risk-sensitive decisions of foraging rufous hummingbirds

There is substantial evidence that an animal's current energy budget affects its preference for food patches that provide a constant reward relative to patches that provide a variable reward, when both patches have the same mean reward. Animals currently on a positive energy budget are expected to choose the constant option, whereas animals on a negative budget are expected to use the variable option. There is increasing evidence that prior experience can affect an animal's current decisions. We investigated choices made by rufous hummingbirds when they were tested with strong or weak sucrose solutions after several days of foraging on those strong or weak solutions. Foraging from weak concentrations prior to and during testing led to a higher preference for the variable option, whereas foraging from strong concentrations led to an increased preference for the constant option. We suggest that the energetic conditions experienced by animals prior to testing had a significant impact on the animals' risk-sensitive decisions, and their memories of those prior conditions may have played an additional role. This implies that the conditions animals are maintained under prior to testing may significantly affect the outcome of risk-sensitivity experiments. Key words: decisions, foraging, hummingbirds, past, risk-sensitive. [Behav Ecol 21:626-632 (2010)]