According to Charles Wolfe "Sweet Fern was a song AP found in his collecting trips into the east Tennessee hills; more commonly known as Sweet Bird, it was written and copyrighted in 1876 by Thomas Westendorf and George Persley. It shows up in a number of southern folksong collections and had even been recorded the year before (1928) by West Virginia singers Orville Reed and Richard Harold.

According to the Meade, Spottswood and Meade discography 'Country Music Sources', Fred Pendleton and Arville Reed recorded 'Sweet Bird' as a vocal duet under their own names in December 1927 and as The Virginia Night Owls in March 1928. Sid Harkreader and Grady Moore also recorded it in March 1928. Richard Harold recorded it in October 1928 with guitar and fiddle backing, but musicians names were not listed. The Carters issued recordings under the 'Sweet Fern' title in 1929 (twice), 1935 and 1936. Fields Ward and His Grayson County Railsplitters also recorded a version in 1929 under the title 'The Birds Are Returning'. There were several recordings in the 1930s under a variety of titles by Bob Cranford and A.P. Thompson (1931), Sweet Violet Boys (Prairie Ramblers) (1936), Aunt Idy Harper and the Coon Creek Girls (1938) and (Charlie) Monroe's Boys (1939).

The Carter's biographers Mark Zwonitzer and Chas. Hirshberg report in "Will You Miss Me when I'm Gone":

"meanwhile Gladys (AP and Sara's daughter) always insisted her father authored the song. "I can tell you where Daddy wrote a song one time." she said in 1990. "Right over behind the house here. The blackberries were ripe. . . and there's a little old bird up in the tree a-singin' and Daddy was a-throwin berries,and he come back-- Sweet Fern. He got the tune to it from that bird a-singin' to him and (the berries a-hittin' the bucket. And he come back and said "Sary,I thought up a song, and he wrote it and they made that record."
'the historian and the daughter are probably both right, in a way. Like as not, AP did get some lyrics for Sweet Bird. . . and like as not, he did get the idea for the call-and-response arrangement from his blackberry expedition. And like as not, Sara and Maybelle took AP's notion and remade the melody and instrumentals into something barely suggested by the old sheet music."

SWEET FERN- Carter Family 1929

Springtime is coming sweet lonesome bird,
Your echo in the woodland I hear;
Down in the meadow so lonesome you're singing,
While the moonlight is shining so clear.

Chorus: But I know he's away in a far distant land,
A land that's far over the sea;
Go fly to him singing your sweet little song,
And tell him to come back to me.
Sweet Fern, Sweet Fern,
Oh, tell me is my darling still true;
Sweet Fern, Sweet Fern,
I'll be just as happy as you.

Yodel: O-dell-eeho-eeho-layhee, edell-leo-leo-layhee,
Ay-leo-lay-dee-hee-oh-leolayhee.

2. Oh tell me sweet fern is he thinking of me
and the promise we made long ago;
He said he'd return from far over the sea
oh why do the years go so slow. Chorus/Yodel

3. And upon my finger he placed a small ring
on the day he was leaving his home;
I said I would be his own dear little girl
and would love him wherever he'd roam. Chorus/Yodel