Chestnut-backed thornbird  (Phacellodomus dorsalis)

The chestnut-backed thornbird is classified as Vulnerable (VU) on the IUCN Red List (1).

The largest of the thornbirds (3), the chestnut-backed thornbird (Phacellodomus dorsalis) has mainly reddish-brown plumage with, as its common name suggests, a chestnut-coloured back. The reddish-brown crown has pale streaking, while the neck and underparts are more greyish-brown, with reddish-brown speckling on the breast and a reddish-brown tinge to the flanks (4).

The males and female chestnut-backed thornbird are similar in appearance (3), while juveniles can be distinguished by the lack of reddish-brown on the crown (4).

The chestnut-backed thornbird has a distinctive iris of either bluish-white or bluish-grey. The long, straight bill of this species is the longest of all species in the genus Phacellodomus (3).

The chestnut-backed thornbird tends to remain hidden, although it often produces rather loud songs (2). The vocalisations of the chestnut-backed thornbird are described as a series of ticking ‘chit-chit-chit-chit-chit’ notes given for long periods with varying intensity. These notes may be given alone, or may accelerate into loud ‘chup-chup-chupchupchuppppp’ notes, which often become quicker at the end (3).

Endemic to Peru, the chestnut-backed thornbird is known from only five or six localities in the northwest of the country (3).

The chestnut-backed thornbird occurs on the eastern slopes of the west Andes in the upper Marañón valley, south Cajamarca and La Libertad. There have also been sightings of this bird on the eastern slopes of the Cordillera Blanca mountain range in Ancash (4).

The chestnut-backed thornbird can be found in dense and tangled thorn-scrub or in the hedgerows of bushy slopes scattered with Prosopis trees. In parts of its range, this species may be found in areas with substantial disturbance, such as along dry streambeds and eroded gulleys adjacent to agricultural areas (4).

Unlike most other thornbirds, which live mainly, if not entirely, in the lowlands (2), the chestnut-backed thornbird is generally found at elevations between 2,000 and 2,800 metres. It has even been recorded to occur as high as 3,400 metres in the Cordillera Blanca mountain range (4).

The chestnut-backed thornbird is usually observed singly or in pairs, typically one to four metres above the ground, searching for arthropods (3). Like other thornbirds, it probably hunts amongst dense bushes and thickets, searching branches, twigs and foliage. It may also peer into curled, dead leaves and will rummage in piles of leaf litter (5).

The chestnut-backed thornbird constructs a large, conspicuous, cylindrical stick nest, which usually hangs from the tip of a tree branch (4). The nests of thornbirds are distinctive, typically having a sideward-facing doorway which gives access to an antechamber. A low sill or ridge separates this from the inner chamber, which contains the eggs (5).

The chestnut-backed thornbird is presumed to be a monogamous species (3), pairing with a single mate for the breeding season to provide better protection and feeding of the young (6).

Habitat destruction in the Marañón valley is the greatest threat to the chestnut-backed thornbird (4). The habitat in this region has already deteriorated significantly due to historical cultivation, and the situation is expected to worsen as cattle-ranching and the spread of oil palm plantations increase (4).

While the chestnut-backed thornbird can cope with some degree of habitat alteration, such as overgrazing and cutting for firewood, it is not known whether it can complete its life cycle in heavily cultivated areas (3) (4).

Although there are no known conservation measures currently in place for the chestnut-backed thornbird, there are several proposed conservation actions. Carrying out a survey to assess the chestnut-backed thornbird’s distribution and population size will help determine which areas need to be protected, while further research into aspects of its biology is also necessary. Finally, it is essential to protect the area around Hacienda Limón, a birding hotspot in Cajamarca (4) (7).

The bird conservation organisation BirdLife International classifies the Río Marañón area as an Important Bird Area (IBA). The IBA system highlights critical sites for the conservation of birds and biodiversity, and will hopefully help in the conservation of this elusive but beautiful species (8).

Find out more

Learn more about the conservation of birds:

• BirdLife International - Chestnut-backed thornbird:
  http://www.birdlife.org/

Find out about conservation in Peru:

• The Nature Conservancy:
  http://www.nature.org/ourinitiatives/regions/southamerica/peru