  In low-collisionality plasmas, anisotropic heat conduction due to a magnetic
field leads to buoyancy instabilities for any nonzero temperature gradient. We
study analogous instabilities in degenerate {\it collisional} plasmas, i.e.,
when the electron collision frequency is large compared to the electron
cyclotron frequency. Although heat conduction is nearly isotropic in this
limit, the small residual anisotropy ensures that collisional degenerate
plasmas are also convectively unstable independent of the sign of the
temperature gradient. We show that the range of wavelengths that are unstable
is independent of the magnetic field strength, while the growth time increases
with decreasing magnetic field strength. We discuss the application of these
collisional buoyancy instabilities to white dwarfs and neutron stars. Magnetic
tension and the low specific heat of a degenerate plasma significantly limit
their effectiveness; the most promising venues for growth are in the liquid
oceans of young, weakly magnetized neutron stars ($B \lesssim 10^9$ G) and in
the cores of young, high magnetic field white dwarfs ($B \sim 10^9$ G).
