  Bifurcation loci in the moduli space of degree $d$ rational maps are shaped
by the hypersurfaces defined by the existence of a cycle of period $n$ and
multiplier 0 or $e^{i\theta}$. Using potential-theoretic arguments, we
establish two equidistribution properties for these hypersurfaces with respect
to the bifurcation current. To this purpose we first establish approximation
formulas for the Lyapunov function. In degree $d=2$, this allows us to build
holomorphic motions and show that the bifurcation locus has a lamination
structure in the regions where an attracting basin of fixed period exists.
