Wrens are birds in the Wren family of birds.
The Wren is the subject of many songs and folktales, possibly going all the way back to Aesop. An Irish song about the Wren can be found in Ulysses by James Joyce:
The wran, the wran, the king of all birds,
On St Stephen's Day he was caught in the furze
Although he is little his family is great;
Stand up old lady and give us a trate
We're hunting this wren all day
Through muddy water and yellow clay,
From bush to bush and from tree to tree
And at Shroneburee he broke his knee.
So up with the kettle and down with the pan
And give me a penny or two-pence to bury the wran
Ulysses James Joyce p481 (8-15)
How did this tiny creature become the high king of all the birds? Well that's not hard to say:
One day the birds were deciding who to elect as their king. It was decided that whoever could fly highest would be crowned. All the birds flew up in the air. The Wren became tired and settled on the Eagle's back. The Eagle flew higher than every other bird but at the last moment when it was finally too tired to continue, the wren, nestled in the eagles feathers, hopped up above the eagle and was subsequently crowned.
a Manx version of this story .