Energy Expenditure in Reproductive Effort of Male and Female Killdeer (Charadrius vociferus)

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Abstract
The reproductive investment strategies of the sexes during the breeding season are detailed for Killdeer (Charadrius vociferus), a monogamous plover. I measured the energy investments of the sexes in reproductive, mating, and parental effort. As predicted, males expend more mating effort than females; however, the sexes expend equal amounts of parental effort. Total energy expenditure in reproductive effort (mating and parental effort) during a successful nesting attempt was also equal for the sexes. However, early parental effort expenditures by females, early mating effort expenditures by males, and high rates of nest failure combine to result in female reproductive energy expenditures being significantly higher over the breeding season. This suggests that energy expenditure alone is not adequate for accurate comparisons of the relative investments of the sexes. Studies investigating male and female investments need to consider the degree and pattern of nest failures along with patterns of energy expenditure. The advantages to male and female Killdeer of sharing parental care is demonstrated using adult removal experiments. In general, a deserted parent expends more energy in parental effort than a bi-parental parent and has significantly lower reproductive success. However, males are able to hatch chicks, whereas females lose or abandon their nests within a few days of mate removal. Thus, monogamy in Killdeer appears to result from high nest failure rates, the necessity of two parents for any reproductive success, and the generalizable nature of Killdeer parental care.