  We study excitations of the spin-1 Bose gas at finite temperatures and in the
presence of a not so strong magnetic field, or equivalently, when the gas
sample is partially polarized. Motivated by the success of two-fluid
hydrodynamics of scalar superfluids we develop a three-fluid hydrodynamic
description to treat the low frequency and long wavelength excitations of the
spin-1 Bose gas. We derive the coupled linear hydrodynamic equations of the
three sounds and evaluate them numerically in a self-consistent mean field
approximation valid for the dilute gas at the intermediate and critical
temperature regions. In this latter region we identify the critical mode.
