bird-dog

also
v. Informal, -dogged, also -dogged, -dog·ging, -dog·ging, -dogs, -dogs.

v.intr.
To follow a subject of interest, such as a person or trend, with persistent attention.

v.tr.

1. To observe or follow closely; monitor: Police bird-dogged the suspect's movements.
2. To seek out (talent or clients, for example): bird-dogs recruits for the team.

verb

To keep (another) under surveillance by moving along behind: dog, follow, shadow, track, trail. Informal tail. See precede/follow.