  A general description of string excitations in stationary spacetimes is
developed. If a stationary string passes through the ergosphere of a
4-dimensional black hole, its world-sheet describes a 2-dimensional black (or
white) hole with horizon coinciding with the static limit of the 4-dimensional
black hole. Mathematical results for 2-dimensional black holes can therefore be
applied to physical objects (say) cosmic strings in the vicinity of Kerr black
holes. An immediate general result is that the string modes are thermally
excited. The string excitations are determined by a coupled system of scalar
field equations in the world-sheet metric. In the special case of excitations
propagating along a stationary string in the equatorial plane of the
Kerr-Newman black hole, they reduce to the $s$-wave scalar field equations in
the 4-dimensional Reissner-Nordstr\"{o}m black hole. We briefly discuss
possible applications of our results to the black hole information puzzle.
