A Whistle

Newbie here - Just a poem as a riddle.

I hear him out the window,
Or out on the street,
He‘s fast like an arrow,
He clearly got speed.

I‘m sure you know him too,
He‘s a companion of many,
His language a whistle,
It‘s almost uncanny.

Though this may make no sense,
For you nor for me,
But when the air is tense,
You‘ll find him be.

On mountains, on sea,
In plains and in towns,
He‘s fast and he‘s free,
Filling the air with his sound.

Have you figured his name?
It is one of fame-
Since every child knows,
Who carries the crows.

I believe that you know,
That you got his name pinned,
‘Cause when you go with the flow
You go with the wind.