This is the original individual at Rincon de Cobo on 22 Feb 08. It was identified as Elegant Tern (Thalasseus elegans) on the basis of bill structure (broad-based, strongly decurved), two-tone bill colouration, long shaggy crest and bulkier appearance relative to Cayenne Tern (T. acuflavidus eurygnathus). Some of these photos were posted on Birdforum and Surfbirds ID forums, with a link to the photos elsewhere on this website sent to ID frontiers.
All bar one of those who posted commented favorably, agreeing with the identification. The other signalled doubt, e.g. in terms of the worn dark primaries that were thought to indicate a bird moulting out of summer plumage (i.e. on a Southern Hemisphere moult cycle), something that ought not to be feasible for a Northern Hemisphere tern - unless it had altered its breeding and moulting cycle (e.g. for reasons of having spent several summers in the Southern Hemisphere, among breeding Thalasseus colonies).
This birds looks off to me for an Elegant. The bill is rather thickset, and the color washed out and odd. I am puzzled too as to why the structure is so similar to that of an adjacent Cayenne, shouldn't an Elegant stand out as being rather different in structure? Slimmer maybe, not so thick bodied. I am not sure exactly what bothers me about this bird, but it just doesn't look right and I see thousands of Elegants both in North and South America each year. Alvaro Jaramillo.