Amazilia alfaroana was first collected in 1895 on the Volcán de Miravalles, in the Cordillera de Guanacaste, north-west Costa Rica (Underwood 1896), and to this day this remains the only known record of this species. In del Hoyo and Collar (2014), which represents BirdLife’s current taxonomic treatment of the species, this taxon was placed as a subspecies of Indigo-capped Hummingbird, A. cyanifrons, a species otherwise endemic to Colombia; while A. alfaroana has also been suggested to be a hybrid by other authorities (see Kirwan and Collar 2016 for a discussion of this). However, following a re-evaluation of the specimen, Kirwan and Collar (2016) have placed A. alfaroana as a separate species, and this treatment is to be recognised by BirdLife International and HBW in 2017.
There have been some further visits to the Volcán de Miravalles that have not been successful in finding A. alfaroana (Stiles and Skutch 1989), but it is not certain how targeted or intensive these were to finding the species (Kirwan and Collar 2016). Recent forest loss at this locality has been minimal (Global Forest Watch 2014) and so any potential remaining population is suspected to be stable, but there remains the likelihood that the species did suffer as a result of habitat loss in the past (Kirwan and Collar 2016). Taking this into account, if the species does persist then the population size is suspected to be extremely small (<50 mature individuals).
This suspected small population size, combined with the lack of any sightings of the species for over 100 years means that the species could warrant a listing of Critically Endangered under criterion D, as the lack of any known targeted surveys for the species mean that it may persist. It would not be appropriate to list the species as Critically Endangered (Possibly Extinct) or Extinct as there has not been sufficient targeted survey effort to be confident enough to move the balance of probability towards its potential extinction.
However, given that there is this extreme paucity of clear information regarding this species it also potentially warrants listing as Data Deficient until further information becomes available. Listing as Data Deficient is only appropriate if it is thought the species’ true status could be anything between Least Concern and Critically Endangered (or Extinct). On balance the species most likely therefore warrants listing as Critically Endangered.
We welcome any comments regarding the listing of this species.
del Hoyo, J.; Collar, N. J. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Global Forest Watch. 2014. World Resources Institute. Accessed on (18/05/2017) www.globalforestwatch.org.
Kirwan, G. M.; Collar, N. J. 2016. The ‘foremost ornithological mystery of Costa Rica’: Amazilia alfaroana Underwood, 1896. Zootaxa 4189(2): 244-250.
Stiles, F. G.; Skutch, A. F. 1989. A Guide to the Birds of Costa Rica. Cornell University Press, Ithaca, NY.
Underwood, C. F. 1896. A list of birds collected or observed on the lower, southern, and south-western slopes of the Volcano of Miravalles and on the lower lands extending to Bagaces in Costa Rica, with a few observations on their habits. Ibis 2(7): 431–451.