“The woods around Penllyne Castle, Glamorgan, had the reputation of being frequented by winged serpents, and these were the terror of old and young alike. An aged inhabitant of Penllyne, who died a few years ago, said that in his boyhood the winged serpents were described as very beautiful. They were coiled when in repose, and "looked as though they were covered with jewels of all sorts. Some of them had crests sparkling with all the colours of the rainbow." When disturbed, they glided swiftly, "sparkling all over," to their hiding places. When angry, they "flew over people's heads, with outspread wings bright and sometimes with eyes, too, like the feathers in a peacock's tail." He said it was "no old story," invented to "frighten children," but a real fact. His father and uncles had killed some of them, for they were "as bad as foxes for poultry." This old man attributed the extinction of winged serpents to the fact that they were "terrors in the farmyards and coverts.”
I once went for a look round the area but found no sign of the elusive beasts. The description if them sounded very much like the fire lizards in Anne Macffrey's Dragon rider books I have always thought.
Oll goes into some depth on the mystery in his post and he did attempt some interviews. His conclusion the creatures as reported are unlikely to exist.