The nightjar
(Book)

"Alice Wyndham has been plagued by visions of birds her whole life...until the mysterious Crowley reveals that Alice is an 'aviarist': capable of seeing nightjars, magical birds that guard human souls. When her best friend is hit by a car, only Alice can find and save her nightjar. With Crowley's help, Alice travels to the Rookery, a hidden, magical alternate London to hone her newfound talents. But a faction intent on annihilating magic users will stop at nothing to destroy the new aviarist. And is Crowley really working with her, or against her? Alice must risk everything to save her best friend--and uncover the strange truth about herself."--Amazon.