Ask the Swan Specialist
Date: 29 April 2007
Thanks for the question. We'll answer one question at a time. First, it is physically impossible for the mallard to have done any thing with the swans. Species don't usually have this happen. There are some species on earth that can impregnate each other, but swans and ducks are not among them.
Secondly, how do you know that the swans were sterile? Are they both males or both females?? Obviously, if they are both male and female, in about 35 days you will find out if the egg is fertile and if you indeed have a sterile or non-sterile pair of swans.
If the swans are both male, they will not lay an egg, but they will mate and will go through building a nest and sit on the nest. The same applies for two female swans. They will mate, and yes, they will go ahead an lay eggs (infertile), and sit on the eggs. In each of these cases, they will get tired when they figure out that nothing is happening and will leave the nest. Nature tells them to do this, so it may take them about a month to realize that they are not going to be parents. Therefore, DO NOT do anything with the egg, it may be fertile.
At this time, there isn't much you can do to protect the egg. If a raccoon, bobcat, coyote, fox or any other predator wants the egg bad enough, they will get it. The swan parents are there to protect and they will protect it as long as they don't lose their lives. A swan, like any other parent, will defend a nest to a point, but if the inevitable happens and they can no longer defend and risk their own life, they will abandon the nest. If you find that you have a fertile pair of swans, you might want to consider a closed pen with access to both land and water for next year's breeding season.
Third, as far a swans running off Canada geese, Good Luck. This happens sometimes and sometimes it does not. We have a 40 acre lake at Lake Morton, Lakeland which serves as our research area with more than 160 swans. The City brings in exotic species such as African, American and Barnacle Geese as well as different duck species. The swans get along fabulously with both. So, don't count on that this is going to be a long term cure to your goose problem.
Finally, you need to feed the swans cracked corn and poultry layer pellets. Bread is not a good food source and it can alter their blood sugar level. A hot dog bun once a day is not going to do any harm and this will be a good way to get close each day to see if the swans are injured or anything is wrong. This will be your bonding time to check the swans physically for any signs of injury or illness.
If we can be of further assistance, please do not hesitate to contact us.