Green’s Dictionary of Slang

1. a woman singer.

1890		Nat. Police Gaz. (NY) 14 June 2/3: Kit tie Burke, known as the‘"Irish Thrush,’ is making a hit out West .
1938		W. Winchell On Broadway 26 Apr. [synd. col.] Toni Lane, the thrush, is at French hosp after a motor accident.
1947		B. Schulberg Harder They Fall (1971) 93: The Latin thrush who beat up the bandleader’s wife.
1953		L. Durst Jives of Dr. Hepcat (1989) 3: From the top of the hill stroll the mellow frames threaded on down and nobody lame. There’s [...] a lush little thrush called Sweetie Pie.
1961		Mad mag. June 44: [in Winchell parody] Tondelyo Furd, the dee-lovely, dee-lightful Broadway and Hollywood nightclub thrush.
1989		H. Rawson Dict. of Invective (1991) 71: canary. A woman, sometimes a whore, and frequently but not necessarily a singer, a.k.a. chirp or thrush.

2. the female pubic hair.

1940s		in Randolph & Legman Ozark Folksongs and Folklore (1992) I 97: Well, I took her ’round the waist an’ I gently laid her down [...] While the blackbird and the thrush were a banging in the brush, / I wound up her little ball of yarn, yarn, yarn.
1992		Randolph & Legman Ozark Folksongs and Folklore I 97: The blackbird is the penis, and the thrush is the woman’s downy pubis.