One thing that did grab me though, which doesn't seem to be in the literature too much (though is mentioned in Birding World's orange-billed tern article from July 2003), is the fair amount of adult birds that do not have fully black legs - pretty crazy orange markings in some birds to rather more subtle markings on the foot base on others. In a flock of 122 Elegant Terns on a San Francisco beach on 9th August 2012, 20% of adults in this flock did not have what I would class as black legs. If you don't remember the putative Cayenne/probable hybrid/generally mashed up looking tern at Cemlyn in June 2006, then have a look at some images here - those leg markings remind me of what several Elegants looked like last week. Perhaps the Anglesey bird was therefore the offspring of a mixed Elegant x Sandwich Tern pairing, as I've not experienced that spangled leg look in any of the other species I've seen - and over the years I've seen a fair few Sandwich, Royal and Lesser Crested Terns.
|adult Elegant Tern with jazzy orange, spangled legs|
|same bird as above, with dependent offspring still begging for food|
|Note the shortened bill on this bird, as it is not a full adult (dark centred tertials and coverts).|
Just a few shots to show the white rumps. I didn't find any birds that showed obviously grey rumps. Admittedly the light was quite bright at times which made assessing this pretty tricky.
And, just to finish off, here are what the 1st year birds look like. Notice the varying leg colour - one bird that I saw had wholly salmon pink legs, to some with seemingly all dark legs.