The Common Gallinule is a bird in the Rallidae family which has been split in July 2011 from the Common Moorhen by the American Ornithologists' Union.
The most obvious physical difference between the two forms is the shape of the birds’ red forehead frontal shield.
​The Old World species Common Moorhen show an elliptical, rounded frontal shield while the New World species Common Gallinule show a wedge-shaped frontal shield, wide and flat at the top, tapering toward the base.

1st & 2nd photo: Shark Valley, Everglades National Park, Florida, USA, 23 November 2012
3rd photo: Eagle Lakes Community Park, Naples, Florida, USA, 21 November 2012
4th photo: Merritt Island, Florida, USA, 23 March 2022