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Acanthidops bairdii - Peg-billed Finch - Poas Volcano, Costa Rica - 7-23-2012 - Brad Weinert (7984324459)

Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Cladus: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Subsectio: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauria
Ordo: Saurischia
Cladus: Theropoda
Cladus: Neotheropoda
Infraclassis: Aves
Ordo: Passeriformes
Subordo: Passeri
Infraordo: Passerida
Superfamilia: Passeroidea

Familia: Thraupidae
Genus: Acanthidops
Species: Acanthidops bairdi

Acanthidops bairdi Ridgway, 1882

Holotype: USNM 85549, 10 Oct 1880.
Type locality: Volcán de Irazú, Costa Rica.


Acanthidops bairdii orth. err.
Haplospiza bairdi (Ridgway, 1882)


Ridgway, R. 1881. Notes on some Costa Rican Birds. Proceedings of United States National Museum. 4 no.235: 333–337. Government Printing Office. Washington [1882]. DOI: 10.5479/si.00963801.235.333 BHLReference page. Original description p. 336 BHL

Vernacular names
English: Peg-billed Finch
español: Yal costarricense
français: Bec-en-cheville gris

The peg-billed finch, Acanthidops bairdi, is a passerine bird endemic to the highlands of Costa Rica and western Panama. Despite its name, it is not a true finch, but now recognized as a member of the tanager family (Thraupidae), after being long placed in the Emberizidae. It is the only member of the genus Acanthidops. The scientific name commemorates the American ornithologist Spencer Fullerton Baird.


The peg-billed finch was formally described in 1882 by the American ornithologist Robert Ridgway from a specimen collected near the Irazú Volcano in Costa Rico. To accommodate the new species Ridgway introduced the genus Acanthidops and coined the binomial name Acanthidops bairdi.[2][3] The genus name combines the Ancient Greek akanthis meaning "spiky" with ōps meaning "face". The specific epithet honours the American naturalist Spencer Fullerton Baird.[4] No subspecies are recognised.[5]


The peg-billed finch is a long-tailed species, 13.5 cm long and weighing 16 g. It has a distinctive long upturned bill with a black upper mandible and yellow lower mandible. The adult male is slate grey, becoming paler on the belly. The female is olive-brown above, becoming paler below and with a grey tinge to the head and upper back. She has bright cinnamon wing bars and buff supercilia. Young birds are similar to the female, but have paler plumage and weaker wing bars.

It has a dry pzeek call, and the male's song consists of high whistled notes ending with a buzz, chee shee shee shee paah.

This is an uncommon bird at the edges and clearings of mountain forests, and in scrubby second growth, bamboo clumps, and bushy pastures from 1500 m altitude to the timberline. In the wet season it can descend to 1200 m altitude. Its numbers have reported to be high when the bamboo is flowering on favoured sites such as Cerro de la Muerte.

The finch is seen singly, in pairs, family groups or in mixed-species feeding flocks with other small birds such as warblers.

The nest, built by the female, is a cup of plant material into which she lays typically four eggs. The female alone incubates for 12–14 days to hatching.

It feeds on insects and spiders, grass and bamboo seeds. It will also squeeze nectar from flowers and juice from berries.

BirdLife International (2012). "Acanthidops bairdi". IUCN Red List of Threatened Species. 2012. Retrieved 26 November 2013.
Ridgway, Robert (1882). "Notes on some Costa Rican birds". Proceedings of the United States National Museum. 4 (235): 333–337 [335–336]. doi:10.5479/si.00963801.235.333.
Paynter, Raymond A. Jr, ed. (1970). Check-List of Birds of the World. Volume 13. Cambridge, Massachusetts: Museum of Comparative Zoology. p. 111.
Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 29, 99. ISBN 978-1-4081-2501-4.

Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (July 2020). "Tanagers and allies". IOC World Bird List Version 10.2. International Ornithologists' Union. Retrieved 5 November 2020.


Stiles and Skutch, A guide to the birds of Costa Rica, ISBN 0-8014-9600-4

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