  We investigate the pion-mass dependence of the nucleon mass within the
covariant SU(2) baryon chiral perturbation theory up to order p4 with and
without explicit Delta(1232) degrees of freedom. We fit lattice QCD data from
several collaborations for 2 and 2+1 flavor ensembles. Here, we emphasize our
Nf=2 study where the inclusion the Delta(1232) contributions stabilizes the
fits. We correct for finite volume and spacing effects, set independently the
lattice QCD scale by a Sommer-scale of r0 = 0.493(23) fm and also include one
sigma pi-N lQCD data point near Mpi = 290 MeV. We obtain low-energy constants
of natural size which are compatible with the rather linear pion-mass
dependence observed in lattice QCD. We report a value of 41(5)(4) MeV for the
sigma pi-N term in the 2 flavor case and 52(3)(8) MeV in the 2+1 flavors case.
