Here is a very literal English translation (as I already said, I never was a poet, nor was I a native English speaker either)

SONG/SINGING OF THE BIRDS

When they see the brightest star
Rise up
In the happiest night
The singing little birds
Are going to celebrate it
With their honeyed voices.

The imperial eagle
Flies off high in the sky
And sings its melody,
It says "Jesus was born
To save us from sin
And to give us joy"

The sparrow answers it:
"Tonight, Christmas night,
Is the one of great happiness"
The greenfinch and the siskin
Say singing too
"Oh, what a joy I feel"

The linett sang
"Oh, how beautiful
Mary's child is!"
And the thrush answers:
"Death is defeated,
Now my life was born!"

The nightingale trills
"He's prettier than the sun,
Brighter than a star"
The black restart and the stonechat
Celebrate the baby
And the Virgin his mother.

The wren was singing
For God's glory
And was embroidering
The canary follows
Their music's sounding like
A great, celestial melody.

Then the lark enters
Saying:"Birds, come
Celebrate the dawn"
And the whistling blackbird
Was celebrating
The greatest Lady

The great tit said :
"It's neither Winter nor Summer
But it's Spring indeed
Since a flower was born
That spreads its perfume everywhere
And fills the whole earth with it.

The francolin was singing
"Birds, who wants to come
Today at the break of day,
To see the great Lord
In his splendour,
In a cowshed?"

The hoopoe is singing
"Last night came
The greatest King"
The turtle dove and the pigeon
Surprise everyone
By singing without sadness.

Woodpeckers and bullfinches
Fly in the orchards
Singing their joy;
The quail and the cuckoo
Have come from far away
To admire the Messiah

And the partridge was singing
"I'm going to build my nest
In this cowshed
To see the Child,
All shaking
In Mary's arms"

The magpie, the thrush or the jay
Say "Here's the month of May!"
The goldfinch answers
"Every tree is growing green again
Every branch is blooming
As if in Spring"

The chaffinch whispers
"Glory today and tomorrow"
I feel great happiness
When I see this diamond
So beautiful and so shining
In Mary's arms

The barn owl and the owl
As they see the day break (the sun peep through)
Withdraw, embarrassed;
The tawny owl and the eagle owl
Say "I can't look;
Such splendors dazzle me"