Pirre warbler  (Basileuterus ignotus)

The Pirre warbler is classified as Vulnerable (VU) on the IUCN Red List (1).

A rare warbler occupying a tiny area on the border between Panama and Colombia, the pirre warbler (Basileuterus ignotus) is a distinctively-marked, largely olive bird. The crown is chestnut, with black margins, and the forehead is pale greenish-yellow, with a long, pale stripe above the eye (2) (3). The ear coverts are dusky olive (4), while the underparts are largely creamy-yellow, except for some greyish-olive on the breast (5). 

The pirre warbler may also be identified by its song, which is a simple, high pitched, sputtering “tssi-i-i-tit” (3).

With a very small range, estimated at no more than 180 square kilometres, the pirre warbler is only found on Alturas de Nique and Cerro Tacarcuna in Darién, Panama, and north-west Chocó, Colombia (2).

Generally occurring between elevations of 1,350 and 1,650 metres, but sometimes as low as 1,200 metres, the pirre warbler inhabits the lower growth of humid elfin forest (2).

A rare and little-studied species, very little is known about the biology and behaviour of the pirre warbler. However, like other birds of the family Parulidae, also known as the New World warblers or the wood warblers, the pirre warbler probably eats insects, which are gleaned off leaves or stems as its weaves its way through the foliage of bushes and trees. Fruit or flower nectar may also be consumed (6). 

There is also almost nothing known about reproduction in the pirre warbler. However, New World warblers tend to be fiercely territorial during the breeding season. They typically form monogamous, but often polygamous, pairs, with the female doing most of the nest construction, as well as the incubation, which lasts for 10 to 14 days. The chicks usually remain in the nest for 8 to 12 days before fledging (6).

Although there are currently no known major threats to the pirre warbler, its extremely small range makes it vulnerable to habitat loss. Future human developments, including the construction of the Pan-American Highway, may threaten this species’ habitat. Forest in the region is currently being cleared and degraded by mining, agriculture and cultivation of coca (2).

The majority of the range of the pirre warbler is contained within the Darién National Park, Panama, and this species also occurs in Katíos National Park, Colombia. However, habitat loss continues in these protected areas, although mostly at lower altitudes (2). 

Recommended conservation measures for the pirre warbler include conservation management schemes to control activities threatening birds in Darién, further studies in the Panamanian part of its range, which has not been surveyed since the 1970s, and the creation of a protected area in the Colombian sector of Cerro Tacarcuna (2).

Find out more about the pirre warbler:

• BirdLife International - pirre warbler (May, 2011)
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=9186