A System that automatically weighs, identifies and determines the direction of penguins moving between their breeding colony and the sea is described. Data obtained from it for a complete colony (589 nests from which 412 chicks were fledged) and related to the foraging ecology of the Adélie penguin Pygoscelis adeliae are presented for the period hatching to fledging. These were obtained at Bechervaise Island (total Adélie penguin population 1816 nests) near Mawson Station Antarctica during the 1991/2 breeding season. The System logged more than 80,000 penguin crossings over a period of three months. Results show that from hatching (20 Dec-10 Jan) onward males and females deliver a similar mass of food to the chick per visit despite males being approximately 480g (11.5%) heavier when empty. A mass of forty five kg was delivered to the colony for each chick raised to fledging. The average fledging weight was 3.1kg. The value of the System for large scale data collection in long term monitoring and ecological studies is discussed.