This is the 1623rd most frequent Polish word.
młodego
"Young" (genitive or accusative singular form of "młody").
The word 'młodego' is in the accusative case, describing the gender and case of 'ptaka', which is masculine singular.
W ogrodzie widziałem młodego ptaka.
I saw a young bird in the garden.
Here, 'młodego' is used in the genitive case in a construction that would often require the meaning of 'with the young'.
Rozmawialiśmy z młodego sąsiadem.
We talked with the young neighbor.
In this case, 'młodego' is in the genitive case to denote possession or attribution, echoing 'for the young'.