We developed an identification setup enabling automatic detection of the passage of free-living King Penguins implanted with small radio frequency transponders at Possession Island, Crozet Archipelago. An unique feature of the system is the use of antennas allowing automatic detection and identification on pathways up to 8-m wide without the use of flipper bands. We present results on demographic parameters of the King Penguin, and we found an unexpectedly survival rate of immature penguins. Such an identification system can be used for other birds, mammals, or reptiles that use regular pathways.