We have a mating pair of royal mute swans. We usually end up with some babies every year which hatch around the beginning of May. We thought she had eggs early this year since we had a nice spring, but it is June and she is still sitting on two eggs(the other two disappeared). Do swans know when their eggs are infertile? She had knocked a few out of her nest over the years, which we have put back in, only to have her knock them out again. Should we take the eggs away at some point? Will she sit all summer? Also, do swans at some point get too old to have viable eggs?
Yes, swan parents know when the eggs are viable. Incubation begins after the last egg is laid. So, a human count of when incubation begins is usually not accurate.
Because of the severe weather late into the breeding season this year, we are seeing many late hatchings. So, this late nesting should not be of major concern and the eggs should not be disturbed.
The swans will leave the nest once the probability of viability ceases. Nature will not allow oversitting on eggs that have no chance of hatching due to the safety of the parents (i.e., predators).
Yes, female swans do reach an age when they no longer produce eggs. Birds are programmed with the exact number of eggs produced throughout their lifetime as well as the number they produce each breeding season.
Additionally, the younger the female swan is when she first produces eggs, the sooner she stops producing eggs later in life. Conversely, the older the swan is when first producing eggs, the later in life she will produce. This is all about hormones. The Regal Swan