  We study a collection of polar self-propelled particles or polar flock on a
two dimensional substrate with birth and death. Most of the previous studies of
polar flock with birth and death have assumed the compressible flock, such that
the local density of flock is completely ignored. Effect of birth and death of
particles on the flock with moderate density is focus of our study. System is
modeled using coarse-grained hydrodynamic equations of motion for local density
and velocity of the flock and solved using numerical integration of the
nonlinear coupled partial differential equations of motion and linearised
hydrodynamics about the broken symmetry state. We studied the ordering kinetics
as well as the steady state properties of the immortal flock and flock with
finite birth and death rate. The ordering kinetics of the velocity field
remains unaffected whereas the density field shows a crossover from asymptotic
growth exponent $5/6$ for the immortal flock to diffusive limit $1/3$ for large
birth and death rates. In the steady state, the presence of birth and death
rate leads to the suppression of speed of sound wave and density fluctuations
in the system.
