This is the 878th most frequent Russian word.
воздухе
"Воздухе" is the prepositional case of "воздух," meaning "air."
The word 'воздухе' is the prepositional case of 'воздух', used here to indicate 'in the air', describing the location of the birds.
Птицы красиво парят в воздухе.
The birds gracefully soar in the air.
In this sentence, 'воздухе' refers to 'clean air', marking the environment that facilitates breathing.
В чистом воздухе легко дышится.
It is easy to breathe in clean air.
'Воздухе' is in the prepositional case to define the location where the scent is present, painting a vivid image of the surroundings.