Rufous-tailed Xenops
The Rufous-tailed xenops (Microxenops milleri) is a small, specialized bird belonging to the ovenbird family, Furnariidae. Known for its distinctive coloration and acrobatic foraging habits, this species is a resident of the vast tropical forests of South America. While it may be rare or patchy in its distribution, it plays a unique role in the biodiversity of the neotropical canopy.
Key Facts
- Scientific Name: Microxenops milleri
- Conservation Status: Least Concern (IUCN 3.1)
- Size: 10 to 11 cm in length
- Weight: 12 to 13 g
- Primary Habitat: Tropical lowland and evergreen forests
- Diet: Arthropods, including Orthoptera (grasshoppers and crickets)
Taxonomy and Systematics
The taxonomic history of the rufous-tailed xenops has seen significant shifts. Originally placed in the genus Microxenops, it was merged into the genus Xenops during the 1950s. However, genetic data analyzed by 2011 revealed that the species did not belong in Xenops, leading scientists to restore the original genus, Microxenops.
Today, the rufous-tailed xenops stands as the sole member of its genus and has no recognized subspecies.
Physical Description
This bird is compact, measuring between 10 and 11 cm in length and weighing approximately 12 to 13 g. Both males and females share the same appearance. The head features a mostly blackish-brown face accented by a buff-colored supercilium (the stripe of feathers above the eye). Its crown is blackish-brown with golden-buff feather shafts.
The body is characterized by a dark rufescent brown back with wide buff streaks that fade toward the lower back. Its rump, uppertail coverts, and tail are all shades of rufous. The wings are blackish with rufescent brown edges, and the flight feathers display a wide rufous band at the base.
The underparts are particularly vibrant: the chin and throat are pale yellowish-buff with dark olive flecks, while the breast is bright buff with narrow dark olive-brown streaks. This transitions into a bright golden-buff belly with light brownish streaking. Its legs and feet range from yellowish-brown to olive, and the bill is thin and straight, with a blackish maxilla (upper mandible) and a blue-gray mandible (lower mandible).
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Distribution and Habitat
The rufous-tailed xenops is widely distributed across South America. Its range extends from southeastern Colombia, through southern Venezuela and southern Guyana, and into Suriname. It is also found in eastern Ecuador, Peru, northwestern Bolivia, and across Amazonian Brazil as far as Mato Grosso. While there are undocumented sight records in French Guiana, the South American Classification Committee of the American Ornithological Society currently lists its presence there as hypothetical.
This species primarily inhabits terra firme (non-flooded) tropical lowland and evergreen forests, though it is also found in várzea (seasonally flooded) forests. While typically found below 600 m (2,000 ft), it has been recorded at elevations up to 1,100 m (3,600 ft) in Colombia and 1,000 m (3,300 ft) in Ecuador.
Behavior and Ecology
Movement and Social Structure
The rufous-tailed xenops is a year-round resident within its range, meaning it does not migrate. It is often seen foraging alone or as part of mixed-species feeding flocks.
Feeding Habits
Specializing in arthropods, the rufous-tailed xenops has been documented eating Orthoptera. It forages primarily in the sub-canopy and canopy of the forest. To find prey, it gleans from bark, leaves, and moss, often hitching along slender vines and branches. Remarkably, it frequently hangs almost upside down to reach the undersides of branches.
Vocalization
The song of the rufous-tailed xenops is described as a short, fast, high-pitched trill. The volume of this trill rises and falls as the sound increases and decreases.
Conservation Status
The IUCN classifies the rufous-tailed xenops as Least Concern. Although its population size is not precisely known, it is believed to be stable due to its very large geographic range. While it is considered rare to locally common with a patchy distribution, it occurs in numerous protected areas, and no immediate threats to the species have been identified.
| Feature | Details |
|---|---|
| Scientific Name | Microxenops milleri |
| Family | Furnariidae (Ovenbirds) |
| Size | 10–11 cm; 12–13 g |
| Range | Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, Venezuela |
| Habitat | Lowland evergreen forest (Terra firme and Várzea) |
| Diet | Arthropods (e.g., Orthoptera) |
| IUCN Status | Least Concern |
Frequently Asked Questions
What is the diet of the rufous-tailed xenops?
The rufous-tailed xenops feeds on arthropods, and members of the order Orthoptera (such as grasshoppers and crickets) have been specifically documented in its diet.
Where can the rufous-tailed xenops be found?
It is found in the tropical lowland and evergreen forests of several South American countries, including Brazil, Colombia, Ecuador, Peru, Bolivia, Venezuela, Guyana, and Suriname.
How does the rufous-tailed xenops forage for food?
It forages in the forest canopy and sub-canopy, gleaning insects from bark, leaves, and moss. It is known for hitching along slender branches and hanging upside down to reach prey.
Is the rufous-tailed xenops an endangered species?
No, it is categorized as Least Concern by the IUCN. It has a large range, a stable population, and is found in many protected areas.
What makes the rufous-tailed xenops taxonomically unique?
It is the only member of its genus, Microxenops, after genetic data led to its separation from the genus Xenops in 2011.