The zooplankton and flamingo populations of 20 high elevation (3,700-4,700 m) lakes in the Andes of southern Peru were assessed on one to three occasions each. Some of these lakes have cyprinodont fish (Orestias spp.), others do not. Lakes with fish usually have a sparse zooplankton dominated by cyclopoid copepods and chydorid cladocerans; the others tend to have an abundant zooplankton dominated by Calanoid copepods and daphnids or by Artemia. Chilean flamingos (Phoenicopterus chilensis) are usually absent or scarce on lakes with fish and present in large numbers where fish are absent. We suggest that the distribution of this flamingo in the Central Andes, and in South America generally, is determined primarily by the distribution of fish, with which it competes for invertebrate prey. The patterns above are complicated by the impact on Orestias populations of man, of fish-eating birds, and of introduced, non-native fish (Salmo gairdneri, Basilichthys bonariensis).

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