  The lowest Landau level of bilayer graphene has an octet of internal degrees
of freedom, composed from spin, valley and orbital two-level systems. Dominance
of $n=0$ orbitals over $n=1$ orbitals in low energy quantum fluctuations leads
to distinct fractional quantum Hall characteristics compared dominance of $n=1$
over $n=0$. The competition between $n=0$ and $n=1$ orbitals depends
sensitively on particle-hole asymmetry and on Lamb shifts due to exchange
interactions with the negative energy sea, which must be accounted for
simultaneously in assessing the orbital competition. We identify the
circumstances under which $n=1$, which supports strong even-denominator FQH
states with non-abelian quasiparticles, emerges robustly as the low-energy
Landau level.
