According to Petcareguides.org Canaries ability to kill Troll is historical

The Troll Market is located under the Brooklyn Bridge. The BPRD had been searching for it for a long time but never found it. Luckily, directions were found when Johann Kraus possessed a tooth fairy. Coercing a cat eating troll into showing them the way, they made it to the gateway. But the troll refused, even under threat of use of canary. But Krauss uses his ectoplasm to unlock the door.