  We discuss the convergence properties of chiral expansions for the
pseudoscalar and vector charmed meson masses based on the chiral SU(3)
Lagrangian. Conventional expansion strategies as formulated in terms of bare
meson masses are shown to suffer from poor convergence properties. This changes
once the expansion is set up in terms of on-shell masses. We find a rapid
convergence of the chiral expansion from vanishing quark masses up to physical
values of the strange quark mass in this case. Detailed results are presented
at the one-loop level for the D-meson and D^*-meson masses. It is emphasized
that our results do not depend on the renormalization scale. An approximation
hierarchy for the chiral Ward identities of QCD is obtained that keeps the
proper form of low-energy branch points and cuts as they are implied by the use
of on-shell masses. Given such a scheme we analyzed the charmed meson masses as
available on various QCD lattice ensembles. In terms of the determined
low-energy constants we consider the coupled-channel interactions of the
Goldstone bosons with open-charm mesons. For the isospin violating hadronic
decay width of the D_{s0}^*(2317) we predict the range (104-116) keV.
