This is the 2205th most frequent Polish word.
ptaków
"Ptaków" means "of birds" in English.
The word 'ptaków' is the genitive plural of 'ptak,' used here to indicate a quantity or possession of birds.
W parku widziałem wiele ptaków.
In the park, I saw many birds.
Here, 'ptaków' is in the genitive plural form, showing possession ('singing of birds').
Słucham śpiewu ptaków każdego ranka.
I listen to the singing of birds every morning.
In this sentence, 'ptaków' is the genitive plural, used after the verb 'boję się' to denote the object of fear.