I know of seabird researchers who were wanting to identify the fish being
brought back for young puffins and terns, so they trained the field staff by
showing them slides of likely prey species. The many photos were of fish
specimens that had been tossed in the air, to give the anticipated
perspectives of observers. Staff learned to quickly use a few characters
such as fin shape to ID the prey; they usually only had a brief distant
glimpse of the bird with prey before it darted into a burrow or fed the
young.

Kevin Li
Ballard, USA