Sometime between the years 1486 and 1502 A.D., the great-tailed grackle Quiscalus mexicanus, an exotic tropical bird from Veracruz, was introduced into the Valley of Mexico by Aztec Emperor Auitzotl. From there, this species spread to other areas of the Central Highlands, and is today one of the most common birds in that part of Mexico. The example of the great-tailed grackle, along with our knowledge of the extensive traffic of exotic birds that occurred during pre-Columbian times, leads us to suspect that the ancient Indians may have altered the ranges of other Latin American birds. The strange disjunctions and extraordinary distributions that we see today, and which have baffled ecologists for so long, are possibly the result of disturbance to the natural fauna long ago by Indians. THE STRANGE DISTRIBUTIONS of many Latin American birds have long been a mystery to biologists. Incredible disjunctions of thousands of kilometers, inexplicable small ranges, and the presence of tropical species in cold montane habitats are all anomalies which have both baffled and fired the imagination of theoretical ecologists. In recent years, a number of excellent books and papers have been written on the fauna of Latin America (MacArthur 1972, Howell 1969, Haffer 1974, Eisenmann 1955, Darlington 1938, etc.). These publications have stressed such factors as diffuse competition, tropical storms, and past climatic corridors and refugia to explain the present-day distribution of neotropical animals. Yet, while all these factors have doubtlessly influenced the Latin American fauna in many ways, one important factor has been overlooked. That is the possible role that the native Indians may have played in altering bird distributions before the European conquest.