The decline of the Colombian grebe is attributed to wetland drainage, siltation, pesticide pollution, disruption by reed harvesting, hunting, competition, and predation of chicks by rainbow trout (Oncorhynchus mykiss).[3] The primary reason was loss of habitat: drainage of wetlands and siltation resulted in higher concentrations of pollutants, causing eutrophication across Lake Tota. This destroyed the open, submergent pondweed (Potamogeton) vegetation and resulted in the formation of a dense monoculture of water weed (Elodea).[4]
By 1968, the species had declined to approximately 300 birds. Only two records of this bird were made in the 1970s; one seen 1972, and the last confirmed record from 1977 when three birds were seen. Intensive studies in 1981 and 1982 failed to find the species and it is now considered extinct.[5]