  Given a continuous open surjective morphism $\pi :G\to H$ of \'etale
groupoids with amenable kernel, we construct a Fell bundle $E$ over $H$ and
prove that its C*-algebra $C^*_r(E)$ is isomorphic to $C^*_r(G)$. This is
related to results of Fell concerning C*-algebraic bundles over groups. The
case $H=X$, a locally compact space, was treated earlier by Ramazan. We
conclude that $C^*_r(G)$ is strongly Morita equivalent to a crossed product,
the C*-algebra of a Fell bundle arising from an action of the groupoid $H$ on a
C*-bundle over $H^0$. We apply the theory to groupoid morphisms obtained from
extensions of dynamical systems and from morphisms of directed graphs with the
path lifting property. We also prove a structure theorem for abelian Fell
bundles.
