'cy' means 'calendar year' :t:@Nutcracker,
thanks for the confirmation.
I think 'cy' refers to the moult cycle the birds is in, independently from the time of the year.
'cy' means 'calendar year' :t:
When it moults. That's easily definable.I'm a big fan of using cy instead of 1st W etc too. When does one summer plumage change to the following winter one?
I'm a big fan of using cy instead of 1st W etc too. When does one summer plumage change to the following winter one? I think it's more accurate to say what calendar year of it's life a gull is in, without introducing the false precision of summer and winter plumages.
When it moults. That's easily definable.
Calendar years work reasonably well for most Northern Hemisphere species (crossbills, pigeons*, sparrows excepted), but in the Southern Hemisphere, birds within a cohort, or even a single clutch, hatching in different years becomes a very real likelihood - deciding whether say, a Kelp Gull is first or second cy needs knowledge of the exact date it hatched, which is impossible to determine.
* I've seen a newly fledged, 2 cy Wood Pigeon on 2 January :t:
Not sure moult is easily definable - When it moults what? Which tracts of feathers? Moult in herring gulls can take up to 6 months to complete, so do you go from the start or the end of the moult period?
Point taken about the southern hemisphere spp though - I hadn't considered that at all, and it definitely muddies the waters. Still, I think for species when the year of hatching can be determined, the cy system is better.