  We probe the effects of strong disorder (2.4 < kFl < 8.6) on
superconductivity in thin films of niobium titanium nitride and titanium
nitride by measuring the microwave electrodynamics in coplanar waveguide
resonators. We find a gradual evolution of the electromagnetic response with
disorder, deviating from Mattis-Bardeen theory, for both materials. This result
can be understood as due to changes in the quasiparticle density of states,
induced by the short elastic scattering length. The observations are consistent
with a model using an effective pair breaker, dependent on the level of
disorder.
