Categories after AERC classification:
A species recorded in a wild state at least once since 01.01.1951 (natural occurrence)
B species recorded in a wild state between 1801 and 1950 (natural occurrence, former status)
C species introduced by man, purposely or accidentally, which have established self-supporting populations (secondarily natural occurrence)
D species, as to which doubt exists whether they ever occured in a natural way (uncertain origin)
E species from captivity, as well as dragged in or introduced, which have not established self-supporting populations (unnatural occurrence)
Among the national avifauna count species of categories A, B and C (cats D and E see appendix)
The species’ status in Poland:
L aktualnie lęgowy (powyżej 100 par)
l aktualnie lęgowy (do 100 par)
(l) aktualnie nielęgowy (w latach 2008-2015)
P regular visitor
Z zalatujący (pojawiający się rzadko – gatunek podlegający weryfikacji)
z extremely rare vagrant (less than five records)
( ) former status (category B)
[ ] uncertain origin (category D)
x unnatural occurrence (category E)