Do savannah sparrows commit the concorde fallacy?

Summary1.The nest defense behavior of a tundra population of savannah sparrows (Passerculus sandwichensis) was examined to determine the relative importance of past investment and future prospects in determining the observed patterns.2.A comparison of birds initiating nests at various times of the breeding season indicated that the change in renesting potential within a breeding season had little influence on the birds' behavior.3.For a monomorphic, monogamous passerine the prospective reproductive success for males and females is expected to be quite similar. However, the respective patterns of nest defense behavior differed considerably (Figs. 1 and 2) and most closely reflected past investment. These results are discussed in light of parental investment theory.