Measurements of blood progesterone levels during the breeding season of adelie penguins (Pygoscelis adeliae) to determine if foraging trips are synchronised

During the breeding season of adelie penguins, breeding birds undergo periods of fast while their mate is out foraging. A late return by either member of a pair can cause nest failure as late returning females may cause the male to abandon the eggs to avoid starvation or if the male is late in returning at the hatching of eggs, the chicks may starve. Pairs synchronise their foraging trip times to avoid these risks. The possibility of a hormonal level acting as a signal level for returning to the nest was investigated by measuring plasma progesterone levels. Adelie penguins at the Northern rookery, Cape Bird were captured and banded during the courtship/copulation stage. Nests were mapped and monitored on a daily basis to check for the presence of adult birds and date of egg laying. Blood samples were taken at key times during the breeding season. Progesterone and placebo pellets were inserted subcutaneously in the back of the neck of male birds just before they left for the second foraging trip. These birds had their blood sampled at implanting and on return from foraging. All blood samples were analysed for levels of progesterone.