The reproductive performance of black-billed magpies: is it related to mate choice?

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Abstract
The influence of age and dominance on measures of reproductive effort were investigated in 26 breeding pairs of captive black-billed magpies, Pica pica. Pairs with adult males constructed nests faster, initiated clutches earlier, and produced larger clutches than pairs with juvenile males. Age of females did not influence these variables. The results suggest that the reproductive output of males varies with age more than that of females. Thus when choosing a mate, females have a wider range of parental quality to choose from than do males. This may explain why females are more discriminant than males in mate choice. Paternal quality of breeding males was tested experimentally. During incubation, adult males searched longer for food, approached a potential predator more closely, and attacked a territory intruder more often than did juvenile males. This suggests that adult males invest more in parental care than juvenile males. It may also be a reason for female preference of adult males. There were no differences in the above variables between dominance classes of males in either age group. However, since competition among individuals was excluded by the captive situation, the significance of dominance status was probably minimized.
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