-
For captions, the bare minimum i’d put is the species name, location, and like Gabriel said, any particular behavior or other info that makes your shot more interesting (but don’t spread the jam too thin), then see if the contest specifies any other infos to include.
WPY is probably the contest putting the highest value on captions, for they’ve awarded images that couldn’t possibly win without explanation on what was being photographed and why it was special.
Also if you can think of any objections the jury might hold against your photo, I would also use the caption to try debunk them.
For example “I wonder if this is a natural behavior” => explain how you’ve encountered the animal, what happened
For example “this background looks weird, i wonder if that was just painted out in photoshop” => explain you’ve used selective lighting or an artificial background, etc.