Assessing chick growth from a single visit to a seabird colony

We tested an approach to the collection of seabird chick growth data that utilizes a one-time sampling of chick measurements obtained during a single visit to a seabird colony. We assessed the development of Black-legged Kittiwake Rissa tridactyla chicks from a sample of measurements made on a single day during six years and compared these results to linear growth rates (g/day), determined from repeated measurements of the same chicks. We used two one-time sampling methods to obtain indices of chick-condition, 1) overall body-size (wing, head-plus-bill, tarsus) vs. mass, and 2) wing vs. mass; both were consistent with repeated measurements in identifying annual variations in chick growth. Thus, we suggest that chick-condition indices obtained from measurements collected on a single visit to a seabird colony are a useful tool for monitoring chick growth, especially at colonies where multiple visits and/or repeated measurements of individual chicks are impractical.