Time: A Hidden Dimension in the Polygyny Threshold Model

Abstract

Temporal unpredictability in habitat quality has important consequences that affect both males and females of polygynous birds. Males must establish territories before females mate and low habitat predictability during the interim may cause many males to make poor choices. Many males may settle in habitats deemed unsuitable by females later in the season, particularly if the boundary between suitable and unsuitable habitat is structurally indistinct. The optimal ordering of male habitat choices is likely to depend on how predictable habitat quality is in each habitat type as well as on the relative quality of each habitat at the time males make their choices. Habitat uncertainties should cause females to base their mating choices on the most predictable components of success rather than on predictions of overall success. They may cause females to delay choosing males in some habitats until more reliable cues become available if uncertainties in predicting success are initially high but decrease substantially during the mafe selection period. In some cases secondary and monogamous females may achieve similar success but for different reasons. If each class of female is predominantly affected by a different nestling mortality agent, then estimates of how well secondary females do relative to monogamous females may be strongly influenced by unpredictable annual deviations from average conditions when they are based on only a few seasons worth of data. In such circumstances short-term tests of the polygyny threshold model are invalid. Polygynous mating systems involve temporal as well as spatial and ecological components. The polygyny threshold model for explaining such mating systems has been viewed up to now only with regard to spatial variations in habitat and male quality. Since temporal uncertainty is an important component of polygynous mating systems, the inclusion of a temporal dimension in the polygyny threshold model is necessary for fully understanding how males and females choose from among alternative reproductive options within such systems.