bird-dog

bird-dog \BURD-dawg\, verb:

1. To follow, watch carefully, or investigate.
2. In slang, to steal or attempt to steal another person's date.

noun:
1. One of various breeds of dogs trained to hunt or retrieve birds.
2. A person hired to locate special items or people, especially a talent scout who seeks out promising athletes.

"Connors thinks my department is so incompetent that he's sending someone to bird-dog my investigation?
-- Judith A. Jance, Partner in Crime

Smart organizations will assign an employee to bird-dog the consultant from the start and learn everything there is to know about a service or application.
-- Dan Tynan, Escaping Services Addiction, Infoworld, August, 2006.

Bird-dog derives from breeds of dogs used in hunting that are known for their tenacious sense for following birds. The sense "to attempt to steal someone else's date" originates in the 19th century.