[Michael Juster]

The answer to Aldhelm's Riddle 43 is "raven." The Aenigmata were written in the second half of the seventh century in southern Britain, maybe around 675.

Aldhelm's raven is a Christian symbol of rebellion against God (Genesis 8:6-7), but in Riddle 43 it probably has more than a hint of the pagan symbolism too. There were not clean lines between the traditions for many centuries--Aldhelm himself associated God with the pagan tradition by referring to God as "the Thunderer." Nonetheless, in the Christian literature of the time the raven was associated with independence, treachery and intelligence, not so much death, so it would not be incongruous for a raven to deliver this message--perhaps it could even be seen as making amends for not responding to the word of the Lord in the Old Testament.

[I cross-posted with the previous two posts, fyi]

Ravens (corvus in Latin) were common in Late Antique and early medieval literature--the more benign blackbird was not common, I believe, until later than Beowulf. I think Tim/Alan & Heaney are probably right in calling the bird a raven, but you should hold your expectations for clarity down--I think this passage is one of the ones primarily attributable to Alan.