On a previous post I discussed upon the divinity of Rhiannon as a Celtic Moon Goddess. There is a singular detail regarding her figure that had always attracted me a lot, a detail recounted on her appearance in one of the Mabinogi tales: "Pwyll Prince of Dyffed", her power to summon birds upon her.
She appears accompanied by magical birds whose enchanted songs could " awaken the dead and lull the living to sleep".
Let's notice they are "three birds", once again the triad symbolism appears here, an association with the Triple Goddess.
Birds like butterflies often symbolize the flight of the spirits to the otherworld. They possessed supernatural powers, and throughout Celtic mythology, divine entities frequently shape-shift between human and bird form.
Even her mentioned roles on the Mabinogion also carry the triad symbolism so familiar to Celtic mythology: the Otherworld Mistress, the Calumniated Wife and finally the Sovereign Queen.
The myth of Rhiannon represents the transitional point from the pagan rituals of the Horse Goddess cult, into its sublimated form: the chivalric mysteries of courtly love, so present on the Arthurian Cycle.
The myth of Rhiannon is recalled in the first and third Branches of the Mabinogi, although her presence is also felt at the end of the Second Branch. Aside from her son Pryderi, and the latter’s avatar Lleu in the Mabinogi of Math, it can be seen that Rhiannon is without doubt one of the most significant characters in the Four Branches as a whole. She plays a leading part in the First and Third Branches, and her presence can be felt to varying degrees elsewhere in the Mabinogi as well.
In Welsh mythology, the Adar Rhiannon; "birds of Rhiannon", are considered thus like supernatural creatures. They belong to goddess Rhiannon and were coveted by the giant Ysbaddaden Bencawr. Let's take a look on each appearance.
Culhwch and Olwen
In the early Arthurian tale, Culhwch and Olwen, the hero Culhwch ap Cilydd seeks the beautiful Olwen, daughter of the giant chief, Ysbaddaden Bencawr. The giant gives Culhwch and his companions forty impossible tasks to be completed before parting with his daughter. The thirteenth task is the gaining of Rhiannon's birds that they may sing at the wedding feast. "These birds have a wonderous song and are ...to wake the dead, and send the living to sleep..."
Branwen, daughter of Llŷr
They are also mentioned in the second branch of the Mabinogi, the tale of Branwen, daughter of Llŷr. Following a catyclasmic war against the Irish, the British king Bendigeidfran orders his seven surviving men to decapitate him, and to return his head to London. Before doing so, they feast at Harlech for seven years, and are regaled by the three birds of Rhiannon:" And there came three birds, and began singing unto them a certain song, and all the songs they had ever heard were unpleasant compared thereto; and the birds seemed to them to be at a great distance from them over the sea, yet they appeared as distinct as if they were close by; and at this repast they continued seven years.'.
Let's notice according to "The Fairy-Faith in Celtic Countries", by W.Y. Evans-Wentz,  that the birds were not in Harlech, they were out over the sea in the atmosphere of Rhiannon's realm in the bosom of Cardigan Bay.
The birds are described as singing 'across the waters' which is the only direct evidence we have for Rhiannon's otherworldly home; the 'Happy Isles of the Blessed'. Thus Rhiannon may origainlly have been the 'Great Queen' of such a realm; a realm to which her steeds transported the spirits of the dead who were entertained on the way by the singing of the 'Great Queen's' magical birds. Her association with Epona and thus between horses and birds also seems to be a recurring theme in Celtic myths.
The Story of the Lady of the FountainThere may also be a hint of Rhiannon's magical birds in the Mabinogion of 'The Story of the Lady of the Fountain'. The Arthurian champion Cynon relates one of his adventures to Oweni and Cei: He comes to a magical glade where a spring emerges.
Water from the spring must be poured on the slab and there will be a mighty peal of thunder and hailstones will fall from the sky. Then the weather becomes fair, but the tree is denuded of its leaves. At this point a flock of birds fly in and they will alight within the bare branches of the tree and sing. Their melody will be the sweetest sound ever heard by any mortal ear. Some time within the course of the song the black knight — guardian of the fountain — will appear to challenge the usurper. For the shower of hailstones will have stripped the black knight's lands bare, denuding it of all life. Only by defeating the challenger can the balance be restored.
Cynon is defeated by the knight but Owein then re-traces Cynon's tracks and experiences the same things but he defeats the black knight. From their description it seems highly likely that the birds described here are the adar Rhiannon (the birds of Rhiannon).
Cambrian poets of an earlier age often allude to the birds of Rhiannon; they are mentioned in the Triads. In a poem of Taliesin's we find Manawyddan and Pryderi joint-rulers of the Underworld, and warders of the very same Cerridwen's magic cauldron of inspiration which the gods of light attempted to steal or capture.
Another of their treasures were the "Three Birds of Rhiannon", which, we are told in an ancient book, could sing the dead to life and the living into the sleep of death. Fortunately they sang seldom. "There are three things," says a Welsh triad, "which are not often heard: the song of the birds of Rhiannon, a song of wisdom from the mouth of a Saxon, and an invitation to a feast from a miser."