The parental time investment and feeding behavior of the North Atlantic gannet (Mórus bassánus (L.)) at Cape St. Mary's, Newfoundland

A study of the parental time investment and feeding behavior of the North Atlantic Gannet (M6rus bass4nus (L.)) with regard to nesting success was conducted at Cape St. Mary's, Newfoundland between May and September, 1977. During five portions of the breeding season 12 nests were observed and five characteristic behaviors of the birds were noted and scored. An analysis of parental time investment reveals that parents spend less time paired together at the nest when chicks are newly hatched and when they are growing most rapidly. During incubation and the first week post-hatch females spend a greater percentage of time at the nest than do the males but following this the roles are reversed. The frequency of nest reliefs is relatively constant throughout the season. Gannet chicks beg at a maximum rate of 1.80+0.19 times per hour when they weigh the most at eight to nine weeks post-hatch. They are fed most frequently (0.214+0.02 times per hour) during three to five weeks post-hatch while growing most rapidly. The parent that is absent from the nest most appears to feed the chick more frequently: the male during one week post-hatch and the female thereafter. As the season progresses, the chicks beg sooner after the arrival of the relieving parent at the nest and are correspondingly fed sooner. The role of parental investment as indicated by these findings is interpreted with reference to the manner in which gannets respond to the apparently seasonally abundant food supply and seasonally favorable climate in order to achieve high nesting success.