One tool we use to study the penguins is an automated weighing and recording system called the APMS (Automated Penguin Monitoring System). This system logs and weighs the birds automatically as they enter and leave the colony (Kerry et al. 1993). It allows us to gather information on the birds without having to manually handle them more than once.
An Adélie penguin crossing the APMS on its way into the colony
Photo by Judy Clarke
Many of the birds can be individually identified by microchips implanted under the skin. These are detected via an antenna near the weighing platform. Two infra-red beams, which are cut sequentially by the birds as they cross the APMS, tell us the direction of travel.
Data from the APMS has been collected annually since the 1991-92 breeding season. This data can tell us much information about the birds, such as their weight change throughout the breeding season, the length of time they have been foraging at sea and the amount of food they have brought back for their chicks.
The graph below shows the mean weights of in-bound and out-bound penguins that have been identified as male, female or fledgling by their implanted microchip. The weights are averaged over five-day periods throughout the chick rearing period (late December to the end of February) during a single breeding season.
Graph of arrival and departure weights of tagged males,
females and fledglings (Fig 4 c from Kerry et al. 1993)
Calculations from this breeding season showed that a total of 18 485 kg of food was delivered to the colony which successfully fledged 412 chicks. This gave a gross estimate of 45 kg of food required to raise each chick to fledging (from Kerry et al. 1993). If there is a food shortage (as was the case in 1994-95) the incoming birds will weigh less than normal and travel in and out of the colony less frequently (Kerry et al. 1995b).
The data collected annually from the APMS can be used to indicate interannual variations in parameters such as foraging trip duration. This can then be compared to other annual data, such as breeding success, to assess what factors are affecting the penguins each year. The chart below displays this kind of annual comparison. It indicates that years of low breeding success are influenced by long foraging trips during the guard stage, particularly long foraging trips of the females (Clarke et al. 2002).
Adélie penguin foraging trip duration in the guard stage in relation to breeding success
