What does "[got] a bird-dog on" mean?

The below Urban dictionary entry makes clear the meaning 'of a guy who is primarily interested in romancing another fellow's girl' - with strong reference to the Everly Brothers' song of that name:

Hey bird dog, lay off of my quail,

Hey, bird dog, go chase your own tail

See entry: http://www.urbandictionary.com/define.php?term=bird%20dog

Bird dog is also a term used in American football for a player who stares down an opponent in the way a dog stares out a bird.

The Bird Dog was a local radio DJ in Austin area of Texas. I asked Steve Earle this very same question a few years back in Perth Scotland.

Bird dog as I know it refers to the radio disc jockey show of the era.

Radio blasting and the BIRD DOG (Disc Jockey) show is on his radio,

They way I see it as an American listening to the song, besides that's what Steve said.

The first four lines of "Guitar Town" are: " Hey pretty baby are you ready for me It's your good rockin' daddy down from Tennessee I'm just out of Austin bound for San Antone With the radio blastin' and the bird dog on "

The very next two lines of are: " There's a speed trap up ahead in Selma Town But no local yokel gonna shut me down ".

It's very clear from this context that Steve's "bird dog" slang means radar detector. Dan in Montreal PS I was in Grade 11 in Toronto when the Everly Brothers "Bird Dog" went #1. PPS In no time!!!

Ok, life long Tennessee boy here. While radar detectors are no longer worth anything because of laser technology. When this song came out everyone had one. Yes, I have heard them called bird dogs by truckers especially. Everyone I knew had one when I was younger. They were not much count unless you were on the interstate because the damn things would go off every time you passed a set of automatic doors.

A “bird dog” on a plane is a radio directional finder. It is (or was) used to navigate, especially to find land when over the ocean or other large bodies of water.

It was repeatedly mentioned in an episode of “Quantum Leap” called “Ghost Ship” in 1992. They were flying through the Bermuda Triangle, and the bird dog was their only means of navigating when other instruments went crazy.

Obviously, that doesn’t apply here, unless he was homing in on a radio station in Austin, Texas (i.e., the signal was getting stronger as he got closer to the city).

https://www.flyingfishaircraftparts.com/products/aircraft-specialty-lines-rdf-2-radio-direction-finder-meter-bird-dog-asl-11933!

a Bird Dog Radio Direction Finder Meter by Aircraft Specialty Lines (https://i.stack.imgur.com/YbFDh.jpg)! (https://i.stack.imgur.com/6Kovn.jpg)