Age codes
23rd February, 2021
For each bird in the gallery, you can find brief information about its sex and age. While sex of the bird is quite straightforward to understand, those alphanumeric codes of age of the bird does not necessarily need to be clear to everyone. But in many northern temperate ringing schemes, correct assessment of the bird’s age is one of the basic and required information a bird ringer must collect. The most common way used in northern temperate regions to age birds is to use the “calendar year” system. Basically, it tells you how many calendar years the bird has lived in (not its age in years – a very common misconception).
So, if a bird is born during let us say May of year one, we can age it as in its first calendar year until December 31st. But immediately the next day, January 1st, it becomes “second calendar year” until the next December 31st. Situation becomes more complicated after the first breeding season of such hypothetic bird – then, most passerines acquire adult plumage which does not change with age furthermore. Therefore, we cannot differentiate between further age groups and we call such bird “older than first calendar year” in autumn and “older than second calendar year” in spring (fig. 1).
Fig. 1: Schematic diagram of the progress of moult in a typical passerine with partial postjuvenile moult (e.g., some chats and finches). Click image to see full resolution.
The system is based on study of each individual bird’s traits used in ageing (mostly moult, which is essential knowledge for ageing) which differ between age groups. For most small passerines we are often only able to differentiate between two most common categories – bird in its first year of life and birds that are older. In some species, we cannot do even that, because in such species postjuvenile moult is complete and there are no plumage differences between the young and adult birds (as in most sparrows and larks; fig. 2).
Fig. 2: Schematic diagram of the progress of moult in a passerine with complete postjuvenile moult (e.g., most sparrows and larks). Click image to see full resolution.
This system is only possible because of vast majority of northern temperate birds breed during quite short period, usually spring and summer. Therefore, all the birds are of relatively same age. In regions where the breeding season is prolonged or spans even two calendar years, calendar year system is not being used as it can lead to nonsense values.
Each bird in the gallery then have in information like this:
- Example temperate: Sex: m, age: 2CY+ (euring: 6), trapped: (…)
In blue is the calendar year code and red is its appropriate euring category. Only birds from tropical region have a simpler age codes being either juvenile or adult (and no euring code ofrcourse). The age codes differ slightly across Europe as some ringing centrals prefer to have the plus sign before, some after and some use slightly different numbering. Most common examples are in this table with some explanation as well as “American” coding.
| This website | Euring | Czech | Ottenby | American | meaning | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| pullus | 1 | pull | NA | L (4) | Usually a bird on nest with downy feathers (or downy young in case of precocial birds - ducks or waders). | |||||
| full grown | 2 | f.g. | NA | U (0) | A bird which is able to fly, not in juvenile plumage but exact age unknown (often birds with complete postjuvenile moult during autumn). | |||||
| 1CY juv | 3J | 1K | NA | J (3) | A bird born certainly this calendar year, still in juvenile plumage. | |||||
| 1CY | 3 | 1K | 1cy | HY (2) | A bird born certainly this calendar year. | |||||
| 1CY+ | 4 | +1K | 2cy+ | AHY (1) | A bird not born this calendar year but some before. Exact age unknown. | |||||
| 2CY | 5 | 2K | 2cy | SY (5) | A bird born certainly previous calendar year. | |||||
| 2CY+ | 6 | +2K | 3cy+ | ASY (6) | A bird not born this or previous calendar years but some year before. Exact age unknown. | |||||
| 3CY | 7 | 3K | 3cy | TY (7) | A bird born certainly the year before previous calendar year. | |||||
| 3CY+ | 8 | +3K | 4cy+ | ATY (8) | A bird not born this, previous or before previsou calendar year but some year before. Exact age unknown. | |||||
| 4CY | 9 | 4K | 4cy | NA | And so on... | |||||
| 4CY+ | 10 | +4K | 5cy+ | NA | ||||||
| 5CY | 11 | 5K | 5cy | NA | ||||||
| 5CY+ | 12 | +5K | 6cy+ | NA | ||||||
| 6CY | 13 | 6K | 6cy | NA | ||||||
| 6CY+ | 14 | +6K | 7cy+ | NA | ||||||
Euring code is the way age is coded in all European schemes. Whether each particular scheme uses 3cy+ or +2K in its central database and in communication with its ringers, it is still coded by the same code somewhere as a code number 6. Therefore, knowing appropriate euring codes to your local ageing scheme can clarify you the age of the bird[1] in case you find system on this webpage unfamiliar. Or of any other European scheme.
I hope this information helped you.
Enjoy the gallery.
[1] More information about EURING codes can be found here: agecodes.pdf [10.32 kB] at BTO website.