The Peg-billed Finch, Acanthidops bairdii, is a passerine

Passerine

A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...

 bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

  which is endemic to the highlands of Costa Rica

Costa Rica

Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....

 and extreme western Panama

Panama

Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

. Despite its name, it is not a true finch

Finch

The true finches are passerine birds in the family Fringillidae. They are predominantly seed-eating songbirds. Most are native to the Northern Hemisphere, but one subfamily is endemic to the Neotropics, one to the Hawaiian Islands, and one subfamily – monotypic at genus level – is found...

, but now recognized as a member of the tanager

Tanager

The tanagers comprise the bird family Thraupidae, in the order Passeriformes. The family has an American distribution.There were traditionally about 240 species of tanagers, but the taxonomic treatment of this family's members is currently in a state of flux...

 family (Thraupidae), after being long placed in the Emberizidae

Emberizidae

The Emberizidae are a large family of passerine birds. They are seed-eating birds with a distinctively shaped bill.In Europe, most species are called buntings. In North America, most of the species in this family are known as sparrows, but these birds are not closely related to the sparrows, the...

. It is the only member of the genus Acanthidops. The scientific name commemorates the American ornithologist Spencer Fullerton Baird

Spencer Fullerton Baird

Spencer Fullerton Baird was an American ornithologist, ichthyologist and herpetologist. Starting in 1850 he was assistant-secretary and later secretary of the Smithsonian Institution in Washington, D.C...

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Description

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

Supercilium

The supercilium is a plumage feature found on the heads of some bird species. It is a stripe which runs from the base of the bird's beak above its eye, finishing somewhere towards the rear of the bird's head. Also known as an "eyebrow", it is distinct from the eyestripe, which is a line which runs...

. 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.

Habitat

This is an uncommon bird at the edges and clearings of mountain forests, and in scrubby second growth, bamboo

Bamboo

Bamboo is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family....

 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

Cerro de la Muerte

Cerro de la Muerte is the highest point in the Costa Rican section of the Inter-American Highway. Its name means "Mountain of Death", since in the past crossing the mountains from the Valle Central meant a three or four day journey, on foot or on horseback, and many ill-prepared travelers...

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Behaviour

The finch is seen singly, in pairs, family groups or in mixed-species feeding flock

Mixed-species feeding flock

A mixed-species feeding flock, also termed a mixed-species foraging flock, mixed hunting party or informally bird wave, is a flock of usually insectivorous birds of different species, that join each other and move together while foraging...

s with other small birds such as warblers

New World warbler

The New World warblers or wood-warblers are a group of small, often colorful, passerine birds restricted to the New World. They are not related to the Old World warblers or the Australian warblers....

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Breeding

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.

Feeding

It feeds on insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s and spider

Spider

Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...

s, grass and bamboo seeds. It will also squeeze nectar from flowers and juice from berries.