  With a peak luminosity of ~10^47 erg/s, the December 27th 2004 giant flare
from SGR1806-20 would have been visible by BATSE (the Burst and Transient
Source Experiment) out to ~50 Mpc. It is thus plausible that some fraction of
the short duration Gamma-Ray Bursts (sGRBs) in the BATSE catalogue were due to
extragalactic magnetar giant flares. According to the most widely accepted
current models, the remaining BATSE sGRBs were most likely produced by compact
object (neutron star-neutron star or neutron star-black hole) mergers with
intrinsically higher luminosities. Previously, by examining correlations on the
sky between BATSE sGRBs and galaxies within 155 Mpc, we placed limits on the
proportion of nearby sGRBs. Here, we examine the redshift distribution of sGRBs
produced by assuming both one and two populations of progenitor with separate
Luminosity Functions (LFs). Using the local Galactic SGR giant flare rate and
theoretical NS-NS merger rates evolved according to well-known Star Formation
Rate parameterisations, we constrain the predicted distributions by BATSE sGRB
overall number counts. We show that only a dual population consisting of both
SGR giant flares and NS-NS mergers can reproduce the likely local distribution
of sGRBs as well as the overall number counts. In addition, the best fit LF
parameters of both sub-populations are in good agreement with observed
luminosities.
