"They travelled until they came to the Blackbird of Cilgwri"
Blackbird
Creative Commons AttributionBlackbird - Credit: jipe_dk

In ascending order of antiquity, the five ancient animals and birds whose advice is sought are: the Blackbird (referred to in other translations as the ousel or ouzel); the Stag of Rhedynfre;  the Owl of Cwm Cawlwyd;  the Eagle of Gwernabwy; and the salmon of Llyn Lliw.

In contemporary Welsh, Cilgwri is the name given to the Wirral Peninsula in northwest England, situated between the estuaries of the River Dee and the River Mersey. Rhedynfre (‘Fern hill’) is the old Welsh name for the village of Farndon in Cheshire. The situation regarding Cwm Cawlwyd is less clear: Lady Charlotte Guest’s translation of The Mabinogion notes ‘there is a place of this name in Caernarvonshire, and another in Carmarthenshire’, but it has also been suggested that Cwm Cawlwyd is the Strathclyde area of Scotland. The location of Gwernabwy and Llyn Lliw are also unclear; one suggestion is that the first has some connection with Bodernabwy on the Llŷn peninsula in northwest Wales, and that the second is somewhere in the estuary of the River Severn.

Another ‘ancient animal’, the Toad of Cors Fochno, is referred to in the story ‘The Ancients of the World’ in William Jenkyn Thomas's collection of fairy stories, and in R.S. Thomas’s poem ‘The Ancients of the World’:

The ousel singing in the woods of Cilgwri
Tirelessly as a stream over the mossed stones
Is not as old as the toad of Cors Fochno
Who feels the cold skin sagging round his bones.