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Offspring sex and duration of post-fledging parental care in the sexually size dimorphic Nazca Booby (Sula granti)

Abstract:

The larger sex in sexually size dimorphic bird species generally requires more food than the smaller sex does, but parents often fail to meet the needs of their larger offspring. Here we analyze nest attendance of Nazca Booby (Sula granti, a seabird with female-larger sexual size dimorphism) parents and offspring during the period of mobile dependence, when offspring can fly but still attend the nest to receive meals. We tested the null hypothesis that parental care to male and female offspring during this period does not differ, complementing previous data on the pre-fledging period. We used attendance to infer the duration of parental care by mothers and fathers, separately, with respect to offspring sex. The duration of the parental association with their offspring during this period, and offspring growth, did not differ by offspring sex, and parental care apparently ended when offspring vacated the natal colony. The number of days parents were observed at their nest site during the post-fledging dependency period did not differ by offspring sex. Our results indicate similar parental care for male and female offspring during the post-fledging dependency period, despite female offspring probably requiring more care than males to reach the same level of condition. © The Neotropical Ornithological Society.