Green’s Dictionary of Slang

1. a persistent, tenacious person.

1922		S. Lewis Babbitt (1974) 147: Busier than a bird-dog, not wasting a lot of good time in day-dreaming or going to sassiety teas or kicking about things that are none of his business, but putting the zip into some store or profession or art.
1949		L.P. Boone in AS XXIV:1 36: Bird dog [...] the worker who stays with a difficult task until it is completed.
1973		C. Gaines Stay Hungry 216: He looked around for a place to hide the shoe box [...] by the time he got it stuffed behind a file where a bird dog couldnta found it Thor was back.

2. (US Und.) a contact man for stock and bond thieves.

1931		in W.L. Stoddard Financial Racketeering in DU.
1936		R. Chandler ‘Guns At Cyrano’s’ in Red Wind (1946) 236: Who’s Courtway? Your bird dog?

3. one who lures victims into positions of vulnerability; also as v., to lure a victim.

1935		Sun (N.Y.) 19 Feb. 28/1: The ‘dynamiter’ may use a ‘bird dog,’ a tout who furnishes prospects and talks up the securities among his acquaintances.
1966		R.E. Alter Carny Kill (1993) 78: That’s why you’re so goddam energetically trying to bird-dog it on to me.
1995		R. Campbell Wizard of La-La Land (1999) 213: ‘So, was Kenny a recruiter?’ ‘He might have done some of that, but mostly he was a bird dog.’.

4. (US campus/teen) a young man, bereft of a partner of his own, who attempts to steal a woman from someone else.

1946		F. Eikel Jr ‘An Aggie Vocab. of Sl.’ in AS XXI:1 31: bird dog, n. One who accompanies a couple and is therefore superfluous.
1958		Everly Bros. ‘Bird Dog’ 🎵 Hey, bird dog get away from my quail. / Hey, bird dog you’re on the wrong trail. / Bird dog you better leave my lovey-dove alone.
1970		(con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 101: There were pajama parties and sock hops [...] Only bird dogs cut in on a slow dance.
1974		J. Lahr Hot to Trot 184: Let the bird-dog stew.

5. an assistant, esp. in police or journalism.

1952		W.R. Burnett Little Men, Big World 83: Mush Head’s got all the bird dogs on it. Headline stuff. You know.
1960		D. Hamilton Death of a Citizen 111: I wasn’t going to play delivery boy or bird dog for either of them.
1960, 1975		Wentworth & Flexner DAS.
1986		R. Campbell In La-La Land We Trust (1999) 63: I’m no bird dog for a newspaper.
2023		(con. 1962) J. Ellroy Enchanters 141: I’m guessing he’s a bird dog for [police chief] Bill Parker.

6. a watcher, an observer.

1952		W. Sheldon Troubling of a Star 170: What are you doing smelling around like a bird dog? [...] Trying to get a free peep show on me and Sachiko, eh?
1959		E. De Roo Young Wolves 89: I’m on the athletic scholarship committee, a bird dog for State.
1986		L. Heinemann Paco’s Story (1987) 31: Freelance newspaper bird dogs [...] pulling a nice fast buck for Time and The Washington Post.

7. (US) a third party, posing as a lover, hired by a couple to facilitate the necessary legal provisions (‘just cause’) leading to a divorce.

2021

J. Ellroy Widespread Panic 25: ‘You’re just the bird dog for my divorce’.