I've got 2 mallards, hatched May 3rd, and a big ol' goose, and a black swedish duck. Anyway, I went out to tell them it was bedtime, and get them off my pond, and there were 3, not 2 mallards. The 'extra' mallard was much paler than my mallards, and flew off when I got too close. What is the deal? Is that mallard going to convince my mallards to fly away? Is it going to bring icky diseases to my ducks? or should I just let them hang out????