<p>This study examined the effect of effort on pigeons' choice behavior between alternatives that require waiting and alternatives that require a response during part of the waiting period. Four pigeons were exposed to a concurrent chain schedule with wait and effort links in the terminal links (TL). The wait link followed a fixed-time (FT) schedule, requiring only waiting until reinforcement. The effort link followed a conjunctive fixed-ratio (FR) and FT schedule, requiring specific responses before waiting for reinforcement. The length of the waiting period between the starting TL and reinforcement was the same for both the wait and effort links. Two conditions were applied with FR values of 10 (lower-effort condition) and 20 (high-effort condition) for the conjunctive schedule in the effort link. In general, three birds preferred the effort link in the low-effort condition, whereas the remaining bird did not. However, under the high-effort condition, all birds preferred the wait link. This suggests that the tendency to choose between these alternatives differs depending on the behavioral effort required during the waiting period.</p>