Assessing chick condition
A sample of chicks (taken from 30 nests during the guard stage, or 50 individuals during the crèche stage) are randomly selected from throughout the colony. The chicks are removed from the nest site by hand during the guard stage or caught with a net during the crèche stage, put into a bag and weighed. The flipper is measured using a specially modified ruler and the chick is then released back to the capture site. From these measurements a chick condition index (CCI) is calculated. This can be used to see how well the chicks are growing and to compare chick condition between colonies and years.
Measuring productivity (chicks per breeding pair)
At the end of the season, the number of chicks that have survived is counted to calculate productivity (number of chicks produced per breeding pair).