Offspring growth in the California gull: Reproductive effort and parental experience hypotheses

Measures of adult feeding and foraging behaviour in the California gull, Larus californicus, were related to the growth of their offspring. Offspring showed significantly higher growth when average feeding interval, a measure of the time interval between feedings, and feeding latency following foraging decreased. The amount of time parents foraged was positively related to offspring growth and negatively correlated with average feeding interval. Either (1) increased foraging efficiency with parental age, or (2) increased reproductive effort with age, could explain age-related differences in patterns of feeding behaviour and their impact on offspring growth. However, data on foraging time support only the hypothesis of increased reproductive effort with parental age.