Purple Gallinule

The purple gallinule (Porphyrio martinicus) is a "swamp hen" in the rail family Rallidae. Also known locally as the yellow-legged gallinule.
This is a medium-sized rail, measuring 26–37 cm (10–15 in) in length, spanning 50–61 cm (20–24 in) across the wings and weighing 141–305 g (5.0–10.8 oz). Males, averaging 257 g (9.1 oz) in mass, are slightly larger than females, at 215 g (7.6 oz) on average. The adult purple gallinule has big yellow feet, purple-blue plumage with a green back, and red and yellow bill. It has a pale blue forehead shield and white undertail. Darkness or low light can dim the bright purple-blue plumage of the adult to make them look dusky or brownish, although the forehead shield color differentiates them from similar species such as common gallinules.

http://en.wikipedia.org/wiki/American_purple_gallinule