Female Choice of Mates: A General Model for Birds and Its Application to Red-Winged Blackbirds (Agelaius phoeniceus)

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Abstract
A model of female choice in birds is developed with special reference to red-winged blackbirds. Male characteristics relate to female fitness, and may influence mate choice only if they greatly affect female fitness, are variable and are accurately assessable prior to mating. Female choice in redwings: should not be influenced by the female''s estimate of the male''s future nest defense effort because nest defense seems to have little effect on severity of predation and parasitism losses; should not be influenced by an estimate of the male''s future time investment in feeding young because this investment is small for redwings and the female''s estimate must be inaccurate; should be influenced by the territory''s vulnerability to predation because predation rates are high, variable from area to area and predictable; and should not be influenced by the territory''s vulnerability to cowbird parasitism because parasitism losses are lower and less predictable than predation losses; it should be influenced by the food available to a female on the territory, because starvation rates are substantial, marshes are variable in [plant] productivity, and productivity should be predictable before mating. Male genetic quality could also influence female choice, but this factor''s importance cannot be evaluated as it is not known how strongly offspring fitness is influenced by male genetic quality nor how accurate is the female''s genetic quality estimate. Empirical tests indicate that territory quality influences female choice more than male genetic quality and that male defense effort has little influence.