At the beginning of April, a pair of swans began building a nest on the municipal pond in Bolesławiec, attracting considerable interest from residents. At the very beginning of the season, measures were taken to protect the birds – immediately after construction began, the nest was covered, in order to limit disturbance and provide greater comfort during the breeding period.
An Attempt to Create a Safe Space
Covering the nest was intended to limit pressure from walkers, dogs and other animals. Such measures are increasingly used in urban habitats of waterfowl, where contact with people is very intense.
Despite these efforts, by mid-June it appears that there will most likely be no cygnets this season either.
What Happened to the Brood?
Under natural conditions, mute swans incubate their eggs for approximately 35–41 days. This means that cygnets from the municipal pond in Bolesławiec should have appeared by the end of May or the beginning of June at the latest. The absence of cygnets in mid-June therefore suggests that the brood was not successful.
Why Are There No Chicks?
In May, there were six eggs in the swans’ nest. Despite the nest covering, several factors may have contributed to the loss of the brood:
Predation
The eggs may have been destroyed by predators such as martens, rats or corvids, which can get into even partially protected nests.
Stress Despite the Covering
The covering reduces disturbance but does not eliminate it completely – particularly in places with heavy pedestrian traffic.
Natural Breeding Failure
In mute swans, some or all of the eggs may be unfertilized, or embryos may die during incubation.
A Quiet End to the Season
Although the pair of swans consistently tried to incubate the eggs and had favorable conditions, the absence of cygnets in mid-June means that this year’s brood most likely ended in failure. Unfortunately, this is yet another time the pair has been unable to have offspring.
This does not change the fact that the swans remain a permanent feature of the municipal pond in Bolesławiec and attempt to raise offspring every year.
Update
After the article was published, a reader contacted us and told us that the problem behind the lack of offspring among the swans at the municipal pond most likely lies in unfertilized eggs. In his opinion, this can be checked – the eggs only need to be X-rayed, and it will be known with 100% certainty.
Of course, this would require interfering with the nest and disturbing the birds, which will defend it, but it is the only way to prevent the female swan from having to remain on a nest from which nothing will hatch anyway. The reader told us that he had contacted both the city office and the Klekusiowo center regarding the matter, where he shared his suggestions.
According to the reader, there are currently four eggs in the nest. The female swan is leaving the nest increasingly often. It appears that she will abandon it soon.
