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)