  In this paper, we study the convergence of Yang-Mills-Higgs fields defined on
fiber bundles over Riemann surfaces where the fiber is a compact symplectic
manifold and the conformal structure of the Riemann surface is allowed to vary.
We show that away from the nodes, the YMH fields converges, up to gauge, to a
smooth YMH field modulo finitely many harmonic spheres, while near the nodes
where the conformal structure degenerates, the YMH fields converges to a pair
consisting of a flat connection and a twisted geodesic (with potential) after
finitely many times of blowing-up's. In particular, we prove a generalized
energy identity and give a refined analysis of the neck.
