First recorded by Inez & Charlie Foxx (US #7/R&B #2 1963).
Other hit version by Carly Simon & James Taylor (US #5/UK #34 1974).
From the wiki: “The original single was credited to Inez Foxx with vocal accompaniment by her brother Charlie, as they alternated the lyric on a syllabic basis. Considered something of a novelty song, it was a great success for them upon its release by Sue Records, reaching #2 on the U.S. R&B chart and #7 on the Billboard Hot 100 in late 1963.
“Carly Simon and James Taylor recorded a remake of ‘Mockingbird’ in the autumn of 1973. The track was released as the lead single from Simon’s album Hotcakes, although it was Taylor’s idea to remake ‘Mockingbird’, which he knew from a live performance by Inez and Charlie at the Apollo Theater in 1965, and which song Taylor and his sister Kate Taylor had often sung for fun as teenagers. The Simon-Taylor version rose to #5 on the Billboard Hot 100 in March 1974.”
Carly Simon & James Taylor, “Mockingbird” (1974):