  We investigate the neutral pion photoproduction on the proton near threshold
in covariant chiral perturbation theory with the explicit inclusion of Delta
degrees of freedom. This channel is specially sensitive to chiral dynamics and
the advent of very precise data from the Mainz microtron has shown the limits
of the convergence of the chiral series for both the heavy baryon and the
covariant approaches. We show that the inclusion of the Delta resonance
substantially improves the convergence leading to a good agreement with data
for a wider range of energies.
