If you are speaking about probing, this is the least reliable method of sexing as the sex organs are not fully developed until the cygnets turn one year of age.

The most reliable method is conducted by a licensed veterinarian who takes a feather sample with genetic material attached. The older and larger the cygnets are enhances the probability that genetic material is present. Undeveloped feathers make the collection more difficult, so we would suggest that the cygnets are at least two to three months of age or older before DNA testing. Because there is a fee to this testing, we suggest that the cygnets are older to increase their chance of survival and eliminate costly tests that are useless if the birds do not survive in the first critical months.

Finally, you will need to have some way of identifying the cygnets prior to the testing and following the test which may take up to two weeks to receive the results from the lab. Microchipping or leg bands may be the best, although if the cygnets are too small the microchips may migrate and cannot be read and leg bands may constrict the growth of the leg causing severe injury or the bands may get caught on something entrapping the cygnet.

Since a cygnet should not be separated from the parents until 8-10 months of age, putting off the sequencing until that age will not be a problem. The Regal Swan