Whiskered Tern

With 400mm at f5.6, it would require you 1/640 speed to have at least descent BIF shoot, now thats for the big slower birds. But for more agile smaller birds, you need more shutter speed than normal. Somehow you will suffer less light gathering, thus you will then compensate it with higher ISO.

Thanks Karan, though this was done handheld, it was a 1/8000 sec speed. with ISO 800 @ f5.6, 400mm, that would somehow freeze this tern suspended in the air.