A visit to Edinburgh Zoo with work allowed me to catch up with both free-flying Night Herons today. These birds are thought to be around 18 and 25 years of age (see here) and are presumably regular visitors to the Zoo's sealion enclosure. Well, that's where they were today, both sitting sunning themselves in the Scot's pine overhanging the pool. I did not have time to check them thoroughly for rings, but from their beak deformities they should be individually identifiable with ease.
The first pic shows a bird with a crossed bill tip with a slightly
protruding lower mandible. I assume it has two colour rings on its left
Here are some pictures I found on a photography forum of what appear to be the same two birds taken in March of last year.
These Night Herons are of the North American subspecies hoactli, so here is a shot of a real wild hoactli taken in Monterey Harbour, California in April 2010. Its beak is certainly a little more appropriately shaped... The differences between this race and the European subspecies are subtle, but the shape of the cap and thickness of the white line above the eye differ, as does the colour of the bare parts in the breeding season apparently.
Finally, a shot of one of the new residents...