I have one duck that has flown over the fence and seems to be laying eggs in a hidden nest. Finding a call nest is nearly impossible. When the hen is on the nest they blend in with their surroundings as though they are invisible. Being so small they get under the smallest of vegetation at times; the nest is almost always under/in something so it can't easily be seen from above. To make things even harder, the duck often covers the eggs with grasses when she leaves the nest. Most of the time the calls use the nest boxes I set out, but sometimes... To find them I wait for them to come off the nest to eat then follow them back to the nest. Not terribly bright, the ducks lead me right to the nest.
My mallards and muscovys are easy to find with their bigger size.
