Well, the web says that though native to sub-Saharan Africa, they have been introduced around the world, including the Americas. Quick cell phone photo:
Just one block out of the Roca Verde Gate, Atenas, Costa Rica
Zooming in for a closer look
Atenas, Costa Rica
These don’t have much of a “helmet,” but they are possibly juveniles and I am certain they are the same bird I saw wild in The Gambia, West Africa. Here they were near a stream, but actually in the ditch of a residential street.
For more information, see Helmeted Guineafowl, Wikipedia
Should I add them to my Birds photo gallery? I’m debating. They may be an invasive species?