Northern Beardless Tyrannulet, Camptostoma imberbe

Northern Beardless Tyrannulet, Camptostoma imberbe. Photograph taken within the greater Alamos area, Sonora, December 2017. Photograph and identification courtesy of David F. Smith, Alamos, Sonora.

The Northern Beardless Tyrannulet, Camptostoma imberbe, is a member of the Tyrannidae Family of Tyrant Flycatchers, which has four hundred twenty-five members placed in one hundred one genera, and one of two global species of the Camptostoma Genus. “Beardless” refers to the absence of rictal bristles, which are present on most flycatchers, at the base of the bill. “Tyrannulet,” or a diminutive of “tyrant,” alludes to its aggressive chasing of potential small predators that attempt to prey on its eggs or young. They are known in Mexico as mosquerito imberbe.

The Northern Bearded Tyrannulet is plainly colored, and the sexes are visually identical. They are grayish olive above with a slightly darker crown and nape. Their underparts have a grayish-olive breast, a paler throat, and a paler belly washed with pale yellow. They have blackish wings with dull white wing-bars and edges. Their supercilium is pale, they have dull white lores, a narrow distinct eye-line, and a very narrow indistinct white eye-ring. Winter birds are more olivaceous above and yellowish below. Their bill is arched, compressed, curved, narrow and short with a black upper mandible, a dusky pink lower mandible that darkens toward the tip; their iris is dark brown; and, their legs and feet are dark brown, blackish brown or lead-colored.

The Northern Bearded Tyrannulet is found within deciduous forests, and brushlands with trees that are at least 8 m (26 feet) in height, with flowing waters adjacent but not always present, at elevations up to 2,100 m (6,900 feet). They are North America’s smallest flycatcher. They consume insects, small berries, and seeds. They are difficult to locate in the wild and are known for their song and normally heard before they are seen. They are monogamous breeders with the females constructing an elaborate, domed, globular nest with a side entrance. They vigilantly care for their young. They have life spans of up to six years. They are elusive, have been poorly studied and very little about their biology or behavioral patterns has been documented.

The Northern Beardless Tyrannulet is easily mistaken for several other flycatchers including Verdin, Vireo, Warblers and Flycathers of the Empidonax Genus.

The Northern Bearded Tyrannulet is found throughout Mexico with the exception of western Sonora, northwest Sinaloa, the north Central Plateau, and highlands of southeast Chiapas. Their northern populations are short-distance migrants.

From a conservation perspective the Northern Beardless Tyrannulet is currently considered to be of Least Concern, with stable, widely-distributed populations. However, their populations have been significantly negatively impacted by the removal of lowland tropical deciduous forests of coastal Mexico due to widespread farming, cattle-raising, and exploitation of forest resources for wood and other forestry products. Pairs are known to abandon nest sites due to repeated human disturbance.