errrm, they're exactly the same species. You have a couple of very similar species such as American Purple Gallinule and American Coot both of which although supposedly weak flyers have made the transatlantic crossing to the UK on several occasions. It's even likely that your Moorhens have also but they canot be distinguished from the Old World version.

. im just saying that in hours of watching whole bunches of them ive never seen one make it more than a few inches over the water.
Try cherry bombs - that'll get em flying!!!
