  In this article I briefly describe how deep radio surveys may provide a means
to identify variations in the upper end of the initial mass function (IMF) in
star-forming galaxies at high redshifts (i.e., $z\gtrsim$3). At such high
redshifts, I argue that deep radio continuum observations at frequencies
$\gtrsim$10 GHz using next generation facilities (e.g., EVLA, MeerKAT, SKA/NAA)
will likely provide the most accurate measurements for the ionizing photon
rates (star formation rates; SFRs) of normal galaxies since their non-thermal
emission should be highly suppressed due to the increased inverse Compton (IC)
losses from the cosmic microwave background (CMB), leaving only thermal
(free-free) emission detectable. Thus, a careful analysis of such observations
in combination with future ALMA and JWST data, measuring the rest-frame
far-infrared and UV emission from the same population of galaxies, may yield
the best means to search for variability in the stellar IMF at such epochs.
