Right, I've found the words as recorded by Plethyn. I think we're supposed to have automatic line-breaks on the new improved Mudcat so let's see ...

Y Deryn Du *

Y deryn du a'i blufyn sidan
A'i big aur, a'i dafod arian,
A ei di drosta'i i Gydweli
I sbio hynt y ferch rwy'n caru.

Dacw'r ty^, a dacw'r sgubor,
A dacw glwyd yr ardd yn agor,
A dacw'r goeden fawr yn tyfu
O dan ei bôn rwy' am fy nghladdu.

Un, dau, tri pheth sy'n anodd imi
Yw rhifo'r sêr pan fo hi'n rhewi,
A dodi'm llaw i dwtshio'r lleuad
A deall meddwl f'annwyl gariad.

Llawn iawn yw'r w^y o wyn a melyn
Llawn iawn yw'r môr o swnd a chregyn,
Llawn iawn yw'r coed o ddail a blode
Llawn iawn o gariad ydw inne.

(Blackbird on silken wing,
Golden beak, silver tongued,
Fly from me to Kidwelly
To see how fares the girl I love.)

(There's the house, there the barn,
There's the open garden gate,
Over there the great tree growing
'Neath its shade may I be buried.)

(One, two, three things are difficult for me -
Counting the stars on a frosty night,
Reaching up to touch the moon,
Knowing the heart of my dearest love.)

(So full is an egg of white and yellow,
So full the sea of sand and shells,
So full the woods of leaves and flowers,
So full of love am I.)

* Aderyn is "a bird" or simply "bird". Correct Welsh for "the bird" would be "yr aderyn" but orally it becomes "y 'deryn" so the song is known as "Y Deryn Du". Along with several others, I might add; there are a lot of Welsh songs involving blackbirds - particularly as love messengers.

Your version had a couple of errors, but a lot of the other variations are simply a matter of dialect.

Aderyn du a'i blufyn sidan,
A'i big aur a'i dafod arian,
A ei di drosta'i i Gydweli, (close gap in dros ta'i)
I holi hynt yr un rwy'n garu. (no ' after un)

holi = enquire
sbia = espy

Un, dou, tri pheth sy'n anodd i mi,
Yw cyfri'r ser pan fo hi'n rhewi,
A doti'n llaw i dwtsha'r LLEUAD, (close gap in dwtsha'r)
a deall meddwl f'annwyl gariad.

This is just a slightly more dialectal version than Plethyn's (above) ... and probably the more 'original'.

As I said above, the last three verses tend to turn up in various songs and are typical of very traditional forms of verse. The last one, for instance, shows up in "Ar Lan y Mor" (which I think Nigel P. was interested in recently). I think v. 2 is what is classed as a Triban, which lists three things (often impossible, sometimes comic).

Hope that helps.

sian