We report finite-ring calculations revealing that spin-1 ferromagnetic easy-plane chains in a symmetry-breaking field are well described by a weakly interacting Bose gas. The thermally-induced central peak (CP) previously observed by neutron scattering from CsNiF3, and interpreted in terms of solitons, is traced back to annihilation/creation processes of the excitations. Its temperature variation shows a pronounced interaction-mediated saturation. The essential features of the spin dynamics and of the field and temperature dependence of the specific heat can be explained without solitons. We predict corresponding CP phenomena in a large variety of spin systems.