well I don't think mallard mate for life, I had some and the drake had four hens to mate with and when I introduced another drake they didn't mind at all. Geese however I believe do mate for life, so I've heard. Sounds like the hen mallard is trying to nest. Since there is only the two of them, mallard species, they have probably gotten closer than they would have if they were in a larger group. The drake will tend to help fend off predators in some cases. At least mine did. As far as whether or not the geese are sterile, I have no idea. My neighbor had a muscovey duck that thought he was a goose, he was raised with them and would try to mate the female goose. The male goose in turn would attack the duck. Perhaps they are just confused?? I am not a professional by any means, but this is my two cents worth. Hope you figure it out.

Is this a wild or domestic duckling? It must be getting big by now! Do you still have it?

LexiF, my neighbor would agree with you. We live in a subdivision, no ponds, lakes etc...but they have a pool. There are three ducks, one male and two females that show up every spring in their back yard and they sure make a mess on the patio and in the pool. The neighbor chases them away and they end up on our front lawn, we're glad for the fertilizer they leave. However, they would not be welcome on our patio.

Nearly all of the wild geese we see today do not migrate... Back in the early 1960's Canadian Geese were on the endangered list and nearing extinction. There is a Wildlife preservation group called "Ducks Unlimited" that was formed by waterfowl hunters and they began a program of creating habitat and hatching Canadian Geese and a number of different wild duck species which they released into the wild all along the eastern flyway. (Major wildfowl migration route), The problem today is that the geese that were hatched & released have little to no social interaction with the true wild geese, so they have not adopted the habit of migrating. To compound the problem, the geese that were hatched & released do not have the natural fear of man that is present in the true wild geese, so they have no problem with living on any available pond whether its out in the country or right in the middle of an urban area and as a consequence they have become a nuisance in many places.