I have three female Pekin ducks, two cayugas (1 male, 1 female) and a male indian runner. This morning I let them into their pen from the coop. The pen is surrounded by a tall chain link fence and has large pine trees over it. I ran to the store for 30 min and came back and the Indian runner was gone. I don't think he can fly and nothing looked suspicious. The other ducks were acting completely normal. I live in central Illinois. Help!