Chick measurements and stable isotope signatures (Larus fuscus)

Lesser Black-backed Gull (Larus fuscus) chick growth and diet measurements taken (1) in the breeding colony of the Port of Zeebrugge (Belgium) and (2) on aviary-raised chicks. Head length from the external occipital protuberance to the tip of the bill was measured to the nearest mm with a digital caliper, and body mass was measured to the nearest g with a digital scale. Measurements in the field were taken every first, third and fifth weekday, until all remaining chicks had reached 30 days after hatching. Measurements in the aviary were taken upon hatching and, from then on, every 5 days. We inferred chick diets in the field from the stable isotope profile of their innermost right primary feather, and raised chicks in captivity on an either fully marine, fully terrestrial, or 50/50 mixture unrestricted diet.