  We study the dynamics of unipotent flows on frame bundles of hyperbolic
manifolds of infinite volume. We prove that they are topologi-cally transitive,
and that the natural invariant measure, the so-called " Burger-Roblin measure
", is ergodic, as soon as the geodesic flow admits a finite measure of maximal
entropy, and this entropy is strictly greater than the codi-mension of the
unipotent flow inside the maximal unipotent flow. The latter result generalises
a Theorem of Mohammadi and Oh.
