The Atitlán Grebe (Podilymbus gigas), also known as Giant Grebe, Giant Pied-billed Grebe, or Poc, is an extinct water bird, a relative of the Pied-billed Grebe. It was endemic at the Lago de Atitlán in Guatemala at an altitude of 1700 m asl. Thanks to the field work of the American ecologist Anne LaBastille, its decline is comprehensively known. LaBastille observed this species for a period of over 25 years. She has also written a book about this bird called Mama Poc.
The Atitlán Grebe reached a length of about 46"?50 cm. The call and appearance were similar to the Pied-billed Grebe. The plumage was mainly dark brown with white-flecked flanks. The underparts were dark grey flecked with white. The head was almost black and the neck was flecked with dark brown in the spring and white in the winter. The legs were slaty grey. The bill had a bold black vertical band in the middle. The color of the bill varied from white in the spring to brown in other seasons. The irises were brown. It had small wings and was flightless.
The nest consisted of 4 to 5 white eggs. Both parents have shared the rearing of the hatchlings.
The decline of the Atitlán Grebe began in 1958 and again in 1960 after Smallmouth bass (Micropterus dolomieu) and Largemouth bass (Micropterus salmoides) were introduced into Lake Atitlán. These invasive species reduced the crabs and fish which the grebes depended on for food and the fish even killed the grebe chicks. The population of the Atitlán Grebe declined from 200 individuals in 1960 to 80 in 1965. Thanks to the conservation efforts of Anne LaBastille, in 1966 a refuge was established where this species was able to rebound. The population recovered to 210 in 1973. Unfortunately after the earthquake in Guatemala in 1976, the lake bed fractured. An underwater drain led to a fall of the water level and to a further severe decrease of the number of grebes. In 1983 only 32 individuals were left, of which the largest part were hybrids with the Pied-billed Grebe. The last two birds were seen in 1989, and after they disappeared the Atitlán Grebe was declared officially extinct.
- Alaotra Grebe, probably extinct since the late 1980s for analogous reasons.