Common Moorhen, Gallinula chloropus
When I photographed these birds on a Christmas visit to London in 2009, they were considered to belong to a world-wide species, Gallinula chloropus, with the American common name of Common Moorhen. In 2011, the American Ornithological Union split the world-wide species in two, with the Old-World birds retaining the original common and scientific names, while the New-World birds were given the scientific name Gallinula galeata and the common name Common Gallinule, adopted from an earlier American name for the larger species.
It was a cold Christmas season in London in 2009, and the pond at Clissold Park in Hackney, where I photographed the birds shown above and below, was frozen over for most of the time I was there -- hence these pictures of Common Moorhen on ice.
The endangered endemic Hawaiian subspecies shown above, ‘alae ‘ula in Hawaiian, Gallinula chloropus sandvicensis in science-ese, is distinguished by the very broad red shield on the forehead, and the breeding-season red extending further down the legs. Maintaining its fragile hold on existence, it is a possible candidate for recognition as a separate species. Meanwhile, I believe it would presently be classified as part of the Old-World species Gallinula chloropus, or Common Moorhen, as would the other Pacific Island subspecies of the formerly world-wide species that bore those names.