Polygyny and Decision Theory: Testing of a Model in Lark Buntings (Calamospiza melanocorys)

Abstract

The data collected in 1976 fit the model with respect to location and conservative timing of bigamous matings. Via habitat manipulation, the changes predicted by the model were induced with respect to the location and timing of bigamous and trigamous (never observed under natural conditions) matings. The model correctly predicted the individual payoffs (number of fledglings) under both natural (1976) and induced (1977) conditions. The lark bunting female probably does not make a strict decision with respect to 1 season''s maximum utility (number of fledglings) but weighs the seasonal maximum utility against future utilities in terms of the probability of surviving to the next season (which is directly affected by the presence or absence of male assistance). Conservative behavior indicates that the objective of the decision is a maximal lifetime utility which within 1 season combines an optimal number of fledglings and the assistance of a male.