Species

Justification
This species was endemic to Lake Atitlán, Guatemala, but is now Extinct. Its extinction occurred sometime between 1983 and 1986, caused by myriad alterations to its habitat.

Taxonomic source(s)
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Brooks, T. 2000. Extinct species. In: BirdLife International (ed.), Threatened birds of the world, pp. 701-708. Lynx Edicions and BirdLife International, Barcelona and Cambridge, U.K.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

Taxonomic note
The taxon has been considered a large and flight-impaired⁷ subspecies of Pied-billed Grebe Podilymbus podiceps². Hybridisation between the two taxa may have been a factor in the final extinction of P. gigas³.

Distribution and population
Podilymbus gigas was endemic to Lake Atitlán, Guatemala (LaBastille 1974). Its population dropped from c.200 to 80 in the 1960s, but recovered to a high of 232 in 1975 (LaBastille 1984). However, various factors drove the population down to 30 by 1983, and it was extinct by 1986 (LaBastille 1990).

Ecology
It inhabited one freshwater lake.

Threats
Initial population declines were a result of competition and predation by large-mouth bass Micropterus salmoides, introduced into the lake in 1960 (LaBastille 1984). However, increasing pressure on breeding sites from local reed-cutting and from tourism development, along with the murder of the government game warden for the national park during the political unrest of 1982 and falling lake levels following the earthquake of 1976, are likely to be the factors which drove the population to extinction (LaBastille 1990). Drowning in gill nets and disturbance by increasing boat traffic have also been suggested as contributory factors (Collar et al. 1994).

Conservation actions underway
Still listed on Appendix I of CITES.

References
LaBastille, A. 1974. Ecology and Management of the Atitlán Grebe, Lake Atitlán, Guatemala. Wildlife Society, Unknown.

Hunter, L. A. 1988. Status of the endemic Atitlán Grebe of Guatemala: is it extinct? Condor 90: 906-912.

Livezey, B. C. 1989. Flightlessness in grebes (Aves: Podicipedidae): its independent evolution in three genera. Evolution 43: 29-53.

Collar, N. J.; Crosby, M. J.; Stattersfield, A. J. 1994. Birds to watch 2: the world list of threatened birds. BirdLife International, Cambridge, U.K.

Howell, S. N. G.; Webb, S. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford.

LaBastille, A. 1984. Drastic decline in Guatemala's giant pied-billed grebe population. Environmental Conservation 11: 346-348.

LaBastille, A. 1990. WW Norton and Company, New York, USA.

Text account compilers
Brooks, T., Khwaja, N., Mahood, S.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Podilymbus gigas. Downloaded from http://www.birdlife.org on 26/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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