duck throwing up may be poisend from.farmers feild

[ducks rcc]

What do I do I let my dream out and he went in the field while the females stayed and sat on there eggs I went to go put him back in the pen and he throw up .. I picked him up and he started throwing up I'm scared he's my favorite duck and the only one who is friendly any ideas? I also put him in the water bowl and held his head under water so he could swallow some clean water