This is a complicated question depending on species, age of swans, gender and resource availability.

Normally, all adult swan pairs (male and female) species of breeding age (and no anatomical, genetic or other physical disability ) will produce eggs annually. The exception is the Australian Black Swan species which produce two clutches of eggs each year, one in the spring and one in late summer.

If the swan pairs are too young, prior to 2 years of age or an older pair, then egg production may not be viable.

Typically, swans that begin producing young at a younger age tend to stop producing eggs earlier in their breeding lifetime. Conversely, if the pairs start breeding at a later age, then the cessation of egg production stops at a later time in their breeding lifetime.

Swans, like many wildlife species practice a form of contraception known as quasi-stability or carrying capacity of the habitat resources. Swans will never overpopulate their habitat. When resources are scarce, young breeders and those not as successful as some of the older established pairs will not produce offspring until resources are adequate. Conversely, swans will not allow the flock numbers to decrease below what the flock numbers are supposed to be or the species could be come extinct.

Finally, swans will pair and mate with same gendered swans if the opposite gendered swans are not available. Obviously, male swans will not produce eggs and female swans will produce eggs, but not fertile in these gendered pairings. In the case of the females, they may or may not produce eggs annually in this type of pairing. So, there are a lot of factors to be considered when addressing this question. The Regal Swan
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