After the nest has been built, which typically takes 2-3 weeks, the egg laying process begins with an egg being laid every 12-24 hours. Once all the eggs have been laid, which can take 2-3 weeks, they will all be incubated (ie sat on to start the growth process) at the same time with hatching usually 42 days (6 weeks) later.
Swans hatch up to 7 eggs at a time with the expectation of losing several of them. It is not uncommon for all the cygnets to be lost to predators, nor is it uncommon for most of them to survive – it all depends on the location and the natural protection afforded them. As the parents grow older they learn from the experience of previous years.
All female swans feast before nesting as they know food will be harder to come by once they are on the nest – it is normal for them to lose weight during the nesting period.