The reason their feathers are shiny green/bronze is because of structural coloration! Rather than having pigments inside their feathers, Nicobar pigeons have tiny, nanometer-scale ridges on the surface of their feathers. When light reflects off the feather it is distorted in such a way that it appears green/bronze and shiny. Structural coloration is rather common in birds; almost all green and blue feathers are the same way, but the Nicobar pigeon takes it to a whole new level.
Unlike many flocking birds, Nicobar Pigeons are known to fly in columns, sometimes almost single file. The white tail of mature birds serves as a ‘taillight’ for the bird behind it, helping the flock to stay together.
The female Nicobar pigeon lays a single white egg, which is long and elliptical in shape. The egg is incubated by both adults and hatches after around two and a half weeks. The chick is initially helpless and fed a rich crop milk fluid, regurgitated by the adults, who continue to tend the chick until it fledges at about three months.
Nicobar pigeons are Near Threatened on the IUCN Red List. Their population is in decline mainly due to habitat destruction. Illegal capture and hunting is not a primary threat due to the pigeon’s wide range, but will become more of a problem as their habitat decreases. Introduced predators are another aspect that is harming these pigeons.