What do HY, SY and ASY mean?
HY means “Hatching Year”. These are the new martins born during the current spring and summer; they have not yet made their first migration to South America. SY means “Second Year”; these are the subadult martins that have spent only one winter in South America. ASY stands for “After Second Year” and includes all martins that have spent at least two winters in South America; they molt into their adult plumage during their second winter in South America.
