So far, I have seen two Grebe species around: The Pied-billed Grebe, and, far more commonly, the Least Grebe. In "Res. Ecol. Mãe-da-Lua", in 2007, the two species did occupy the same small water reservoir. On several occasions, the Pied-billed Grebe chased and ferociously attacked the Least Grebe and its chicks. Actually, I believe the Pied-billed killed at least one of the chicks.