Yes, the drake-hen ratio should be 1 drake for 3-9 hens. She may be hiding her eggs outside. But nothing happens until she starts to sit on them. Quite honest it is late in the season for having duckling. They need a month to incubate, which brings it to mid October. Then they need about 3 months to get their feathers, which bring it to mid January. This means you have to provide a warm space for them for the entire time. They wont be able to moving around much, and therefore not developing their muscles and legs in a proper way. This wont harm them, just delay them. I always tell people to look 4 months ahead and tell me what the weather will be then. Make your decision accordingly. There is always spring just around the corner. As cute it may be to have ducklings now, it may not be that practical.