Satellite remote sensing in monitoring change of seabirds: use of Spot Image in king penguin population increase at Ile aux Cochons,Crozet Archipelago

The king penguin colony at Ile aux Cochons, Crozet Archipelago (southern Indian Ocean) is the largest in the world. The change in its surface area was investigated by means of satellite remote sensing using spot scene. The satellite picture enabled us to locate the colony and to determine that the surface area occupied by the colony has increased by 56% between 1962 and 1988. The increase in the surface area occupied by the colony was confirmed by a map realised in 1982 (by the Institut Géographique National). The high resolution system available on the spot system which allows at present at 10 m ground resolution, and 5 m in the near future, can thus be a useful tool for monitoring medium to long-term changes in marine bird populations breeding in colonies composed of birds spaced a constant distance from one another. Based on the surface area occupied by the colony and the published data on the population size on Possession Island, as well as information on the breeding frequency of the species, we estimated that the total breeding population is about 1,000,000 pairs for the whole archipelago and that about 70% of birds breed at Ile aux Cochons.