The young are browner and lack the red shield. It has a wide range of gargling calls and will emit loud hisses when threatened. As mentioned elsewhere these are extremely common and very friendly where I live and are fun to watch as they zig-zag across the ground running to see if people walking by have food for them.
The Common Gallinule (Moorhen) is a bird in the Rail family that lives around well-vegetated marshes, ponds, canals, etc. It's a distinctive bird, with dark plumage apart from the white undertail, yellow legs and a red facial shield.