  In this work, taking the QED effect into account, we investigate the shadows
of the Kerr black holes immersed in uniform magnetic fields through the
numerical backward ray-tracing method. We introduce a dimensionless parameter
$\Lambda$ to characterize the strength of magnetic fields and studied the
influence of magnetic fields on the Kerr black hole shadows for various spins
of the black holes and inclination angles of the observers. In particular, we
find that the photon "hairs" appear near the left edge of the shadow in the
presence of magnetic fields. The photon hairs may be served as a signature of
the magnetic fields. We notice that the photon hairs become more evident when
the strength of magnetic fields or the spin of the black hole becomes larger.
In addition, we study the deformation of the shadows by bringing in
quantitative parameters that can describe the position and shape of the shadow
edge.
