Formerly considered a race of the American Coot (F. americana), the Slate-colored Coot is sometimes known as the Andean Coot. I prefer Slate-colored because it actually describes the bird. It is used by Clements/eBird, HM4, and SACC. Andean Coot (used by IOC & HBW) is a misnomer in that this species is also found in the lowlands while other coot species are confined to the Andes. This bird comes in two morphs, one has a yellow bill with a red shield and green legs as seen here, and the other has a white bill, shield, and whitish legs. On our recent visit, we found both types side-by-side in the same pond. Most authorities (HBW, IOC & HM4 but not Clements/eBird) recognize two subspecies with F. a. atrura lacking white in its tail and ranging in coastal Peru south to Lima replacing the nominate white-tailed race further south. Canon PowerShot SX50 HS
References:
Fjeldså, J. (1983) Geographic variation in the Andean Coot Fulica ardesiaca. Bull. Brit. Orn. Club 103:18–22.
Fjeldsa, J. and Krabbe, N. (1990) Birds of the High Andes. Zoological Mus. University of Copenhagen & Svendborg.
Jarmillo, A. (2003). Birds of Chile. Princeton Univ. Press. Princeton.
Slate-colored Coot (Fulica ardesiaca), In Neotropical Birds Online (T. S. Schulenberg, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/slccoo1
Taylor, B. (2018). Andean Coot (Fulica ardesiaca). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53700 on 23 January 2018).