My last trip abroad was to the US and specifically Florida. Unfortunately I visited just a week or so before the main spring migration and birding was not as productive as you would imagine. Particularly, warblers were difficult to locate, however in the area that I stay, Palm Warblers are always easy to find and they make good photographic subjects.  On one overcast and dull evening in the local park I had a magical encounter with a small flock, obviously on migration they were feeding constantly on small insects and flies.  There are two sub-species of Palm Warbler, Eastern and Western and both migrate through the Florida peninsular.