Remember that Child was collecting ballads from a number of sources. In broad Scots (a true dialect), and even several plain old northern accents, the lyric is certainly "walkin' her lane...makin' his mane". And, sure, you can both see and hear a prisoner complaining about his fate, especially if he's putting on a deliberate act to get you to set him free, as in the song.

Remember, Child wasn't quite as willing as, say, Robert Burns, to get down and dirty with commoners. Wealthy, well-educated Scottish and English contributors knew broad speech from their area, but likely spoke to scholars intending to publish in standard English ("If you go to the pub, you'd hear it sung broad, but in *our* home, we use the King's English."). So some of Child is very Anglicised, and some is not.

I think in "The Twa Corbies" the birds are definitely griping, from context, and that two birds' cawing certainly resembles human moaning or whining, just by the sound.