Beka Cooper Terrier - a novel by Tamora Pierce

To the surprise of both the veteran 'Dogs' and her fellow 'puppies', Beka requests duty in the Lower City. The Lower City is a tough beat. But it's also where Beka was born, and she's comfortable there. Beka is assigned to work with Mattes and Clary, famed veterans among the Provost's Dogs. They're none too happy about being saddled with a puppy for the first time in years.
However, Beka has something unique to offer: she hears things that Mattes and Clary never could - information that is passed in murmurs when flocks of pigeons gather.