O’REILLY, K.M.*; IMHOLT, S.M.; COVERDILL, A.J.; WHEELWRIGHT, N.T.: Testosterone and Parental Care in Savannah Sparrows

The influence of testosterone on parental care was studied in Savannah Sparrows (Passerculus sandwichensis). Nests were videotaped when the chicks were five days old. Over 214 hours of videotape taken during three field seasons were analyzed to determine duration and frequency of nest visits by male and female parental sparrows in a marked population at Kent Island, New Brunswick, Canada. Females provided significantly more parental care than males. Blood samples were obtained from the videotaped males and testosterone levels were compared to the amount of parental care provided by the fathers and mothers. Testosterone levels varied from 4.31 ng/ml to 0.05 ng/ml, decreasing as the breeding season progressed (P < 0.001, N = 65). No significant correlation was found between testosterone levels and male parental care as measured by duration and number of visits. However, females mated to males with elevated testosterone levels spent significantly more time at the nest (P = 0.033, N = 40), although the number of visits did not increase significantly. Secondary females mated to bigamists spent significantly more time at the nest and made more visits than primary females.