[5][6] Two subspecies are recognised:[6] Based on cladistic analysis of mtDNA cytochrome b and 12S rRNA sequences, the Nicobar pigeon is sometimes called the closest living relative of the extinct didines (Raphinae), which include the famous dodo (Raphus cucullatus).

[8] The following cladogram, from Shapiro and colleagues (2002), shows the Nicobar pigeon's closest relationships within Columbidae, a clade consisting of generally ground-dwelling island endemics.

The primitive molecular clock used to infer the date the ancestors of the Nicobar pigeon and the didines diverged has since turned out to be both unreliable and miscalibrated.

The Spotted green pigeon (C. maculata) is a more recently extinct species from an unknown Pacific locality; it probably disappeared in the 19th century and most likely succumbed to introduced European rats.

It is placed in Caloenas as the least awkward possibility; its true affinities are presently indeterminate and it is perhaps more likely to represent a distinct genus of the Indopacific radiation of Columbidae.

The cere of the dark bill forms a small blackish knob; the strong legs and feet are dull red.

The 2004 Indian Ocean tsunami caused massive damage on the Nicobar Islands, and to what extent Batti Malv was affected is still not clear.

An April 2007 survey by the Indian Coast Guard vessel ICGS Vikram found the lighthouse tower "totally covered" in vines, indicating rampant regeneration of vegetation – but perhaps also that damage to the island's forest was severe, as a cover of creeping plants is typical of early succession stages, while a photo of the lighthouse taken before the tsunami shows rather mature forest.

Its flight is quick, with regular beats and an occasional sharp flick of the wings, as is characteristic of pigeons in general.

The white tail is prominent in flight when seen from behind and may serve as a sort of "taillight", keeping flocks together when crossing the sea at dawn or dusk.

The offshore islets which it requires are often logged for plantations, destroyed by construction activity, or polluted by nearby industry or harbours.

Also, increased travel introduces predators to more and more of the breeding sites, and colonies of the Nicobar pigeon may be driven to desert such locations or be destroyed outright.