The green-tailed warbler is a small, slender and very active bird, which makes frequent jumps, wing and tail movements, while also turning its head from side to side. The head, neck and throat are gray, while the rest of its upperparts, are olive-green. Its underparts are grayish-white. The eye is circled by a broken white ring. Young birds have a grey iris, which changes to red in adult birds. Its relatively long, green tail is, of course, the source of its common name. The green-tailed warbler resembles a warbler (family Parulidae) in size and overall appearance, and indeed this is where it was originally classified. However, genetic studies now place it in the tanager family (Thraupidae), along with its sister species, the white-winged warbler (Xenoligea montana).
Unlike many species in this family, the green-tailed warbler is more insectivorous than frugivorous. In the cloud forest, it is a delight to observe it feeding on small insects living inside moss and lichens, where its olive-green color perfectly blends with the surrounding vegetation, especially in areas with bamboo vines. Although it has been recorded in montane broadleaf and pine forests (up to nearly 3,000 meters elevation), the green-tailed warbler is also found at lower altitudes, including some areas of dry scrub, desert thorn scrub, and dry broadleaf forest near sea level.
The green-tailed warbler usually forages in thick vegetation near the ground, alone or in pairs, but also regularly joins mixed-species foraging flocks in pine habitat. The calls of the green-tailed warbler consist of a set of squeaky notes, similar to the typical alarm calls of songbirds including a sharp sip – sip – sip. Long-term studies that have marked individual birds have shown that green-tailed warblers can show high site fidelity. Some individuals have been recaptured several times at the same sites, up to seven years later! The green-tailed warbler is quite curious, and often responds quickly to a birder’s spishing sound. It builds a bowl-shaped nest where it lays 2 to 4 pale green eggs.
“From an ébano verde tree with bromeliads, moss and small orchids completely covering its branches, came the sound of an insect. Then another sound. Suddenly there were many songs: toads, frogs, crickets. In this setting the Green-tailed Warbler made its appearance.” Anabelle Stockton de Dod
“…so quiet that it is found only by those accustomed to search for the shyer species of birds.” Alexander Wetmore and Samuel H. Swells
Two subspecies have been described: Microligea palustris palustris, for most of the island, especially mountainous areas, and Microligea palustris vasta, a paler and smaller form on Beata Island (and possibly in other low, dry forest areas in the southern Dominican Republic).
Currently, the green-tailed warbler is not listed by the IUCN or the Dominican Republic as a threatened species. However, a recent study recommends its inclusion in these lists due to a marked decrease in its abundance of over 60%, documented between 1997 and 0 in Sierra de Bahoruco. Its relative high abundance in mid to high elevation forests makes the conservation of these montane forests key to the continued health of its populations.