  We have measured the quantum Hall activation gaps in bilayer graphene at
filling factors $\nu=\pm4$ and $\nu=\pm8$ in high magnetic fields up to 30 T.
We find that energy levels can be described by a 4-band relativistic hyperbolic
dispersion. The Landau level width is found to contain a field independent
background due to an intrinsic level broadening and a component which increases
linearly with magnetic field.
