“Dominica Forest Thrush”

Frontiers of Taxonomy: The Forest Thrush Complex.

The internal taxonomy of the Forest Thrush complex is unresolved and in need of revision.  Recent research suggests that it may consist of multiple species, with the populations on Montserrat and Guadeloupe comprising one species with three subspecies, and the populations on Dominican and St. Lucia both likely recognizable as separate species—although the St. Lucia form evidently died out in the late 1900s.

The “Dominica Forest Thrush”, T. l. dominicensis, differs visibly and vocally from those of Montserrat and Guadeloupe.  Visibly, the Dominica form is darker brown overall and has a white belly, and a finer scaling pattern on the breast and flanks.  Vocally, its song is simpler, choppier, and less musical than “Northern’s”, and includes a sharp upslurred note frequently interspersed (and likely differs in other ways, but few recordings of Forest Thrush songs are available for a more thorough review).

The “St. Lucia Forest Thrush”, T. l. sanctaeluciae, has not been reliably reported in recent decades and is likely extinct.  Although Forest Thrushes are secretive and difficult to see, they are not difficult to hear, so the failure of intensive searches to locate any singing individuals strongly suggests that sanctaeluciae no longer exists.  Documentation of its appearance and song is not readily available, so its distinctness is difficult to evaluate, but geography and the isolation of dominicensis suggest that sanctaeluciae must have been at least as divergent genetically as dominicensis—probably more so given that it was separated by a much greater distance, including the island Martinique, where no subspecies of Forest Thrush has been recorded.

The populations of Montserrat and Guadeloupe—currently designated as T. l. dorotheae and lherminieri—generally resemble one another, but show significant divergence in measurements and genetic markers.  However, the research of Arnoux et al. (2014) indicates that the populations of eastern and western Guadeloupe are more divergent from one another than from the Monstserrat population, which indicates that there should be two subspecies recognized on Guadeloupe.  With recognition of the Dominica and St. Lucia forms as distinct, and named accordingly, the natural designation for the remaining group would be “Northern Forest Thrush,” T. l. lherminieri.