Lawyer and amateur beekeeper Andrew Lloyd sprang into action after the bees swarmed down Liverpool Street on Thursday afternoon and settled on a small tree.

"Being swarming season they were flying around," Mr Lloyd told AAP.

"Then I saw they'd swarmed onto a branch of the tree at a reasonable height to collect."

Mr Lloyd - who had earlier been in court - rushed home to Glebe to pick up a cardboard legal document box, his bee veil and some gloves.

Then he returned to the city and, using his ladder and a stool from a nearby cafe, cut off the branch and gathered the bees into the box.

Experts say the bees would have temporarily landed on the tree while some went looking for a spot to set up a permanent new hive.

Mr Lloyd - who's been keeping bees for five years and supplies a local cafe and restaurant with his honey - relocated the swarm to his place at Glebe where they'll live on the garage roof.

Urban Beehive co-owner Doug Purdie says if someone sees bees swarming they should contact a local beekeeper or the Amateur Beekeepers Association NSW which runs a swarm collection service.

"What people shouldn't do is spray them with water or insecticide or anything like that," Mr Purdie told AAP on Thursday.

Swarming season usually runs from October to November.

Mr Lloyd's unusual day had a final sting in the tail when he collected a motorcyclist with his car after boxing up the bees.

"He (the rider) probably had a dislocated shoulder, but I gave him a jar of honey to sweeten the deal," the solicitor said.

Australian Associated Press