+1 I agree, looks like it's panting...
Both of mine were panting today - I had my 2 out in the yard with me earlier, and it was near 90° outside.
I was sitting in the shaded grass on a deck chair, and both of the ducks were sitting under my chair to keep cool.
I had a bowl of clean, cool water out with us that they would drink from often, and there was a nice breeze blowing as well, but it was still hot out.
Occasionally, they'd head over to their kiddie pool for a bit, then back under my chair.
Sounds like your little one is too warm as well.
Hope he feels better!
Cheers'
Dan