The limestone leaf warbler is a species of warbler in the family Phylloscopidae. When this species was first seen, beginning in 1994, it was mistaken for the similar sulphur-breasted warbler. It is smaller than the sulphur-breasted warbler, and has more rounded wings. The plumage is almost identical, with comparisons showing only a slightly colder yellow below and a greyer tinge above. Although smaller, the bill is proportionally larger than that of the sulphur-breasted warbler. Accurate measurements are not available; the holotype has a wing length of 5.2 cm (2.0 in); the paratype a tail length of 3.7 cm (1.5 in) and a bill length of 1.39 cm (0.55 in). The species is known to occur in northern Vietnam and Laos, and potentially also occurs in southern China as well. The species name, calciatilis, means "dwelling on limestone", which along with its common name is a reference to its natural habitat, which is broadleaved evergreen and semi-evergreen forest growing around limestone karst mountains. The bare-faced bulbul, described in 2009, was found in the karst of the same region.
Region
Indochina
Typical Environment
Occurs in northern Vietnam and Laos, with possible occurrence in adjacent southern China. It is tightly linked to broadleaved evergreen and semi-evergreen forests growing on limestone karst, frequenting slopes, valleys, and ridgelines with rugged outcrops. The species favors relatively intact karst forest and dense foliage where it forages in the lower to mid canopy. It may appear along forest edges and in karst scrub but is uncommon in heavily degraded habitats.
Altitude Range
100–1000 m
Climate Zone
Tropical
Ease of Keeping
Beginner friendly: 1/5
This recently described leaf warbler is specialized for limestone karst habitats and was long confused with the similar sulphur-breasted warbler. It is smaller, with proportionally a slightly larger bill and more rounded wings. Its plumage differences are subtle—cooler yellow below and greyer-tinged above—making voice and habitat strong clues for identification. Its tight association with karst forests makes it sensitive to quarrying and forest degradation.
Global distribution
Temperament
active and somewhat skulking
Flight Pattern
short rapid wingbeats
Social Behavior
Typically forages singly or in pairs, and regularly joins mixed-species flocks in forest. Breeding is assumed to be monogamous, with a small, cup-shaped nest placed in dense foliage or low shrubs, similar to other Phylloscopus warblers. Territorial during breeding, but more tolerant in the non-breeding season.
Migratory Pattern
Resident
Song Description
Delivers a high-pitched, thin series of trills and sibilant notes typical of leaf warblers. Calls are sharp, high seeps that carry in the forest but can be hard to localize.
