  We investigate positive steady states of an indefinite superlinear
reaction-diffusion equation arising from population dynamics, coupled with a
nonlinear boundary condition. Both the equation and the boundary condition
depend upon a positive parameter $\lambda$, which is inversely proportional to
the diffusion rate. We establish several multiplicity results when the
diffusion rate is large and analyze the asymptotic profiles and the stability
properties of these steady states as the diffusion rate grows to infinity. In
particular, our results show that in some cases bifurcation from zero and from
infinity occur at $\lambda=0$. Our approach combines variational and
bifurcation techniques.
