  The Vicsek model of flocking is studied by computer simulation. We confined
our studies here to the morphologies and the lifetimes of transient phases. In
our simulation, we have identified three distinct transient phases, namely,
vortex phase, colliding phase and multi-domain phase. The mapping of Vicsek
model to XY model in the $v \to 0$ limit prompted us to explore the possibility
of finding any vortex kind of phases in the Vicsek model. We have obtained
rotating vortex phase and measured the lifetime of this vortex phase. We have
also measured the lifetimes of other two transient phases, i.e., colliding
phase and multi-domain phase. We have measured the integrated lifetime
($\tau_t$) of all these transient phases and studied this as function of
density ($\rho$) and noise ($\eta$). In the low noise regime, we proposed here
a scaling law $\tau_t N^{-a} = F(\rho N^{-b})$ where $F(x)$ is a scaling
function like $F(x) \sim x^{-s}$. By the method of data collapse, we have
estimated the exponents as $a=-0.110\pm0.010$, $b=0.950\pm0.010$ and
$s=1.027\pm0.008$. The integrated lifetime $\tau$ (defined in the text
differently) was observed to decrease as the noise approaches the critical
noise from below. This behaviour is quite unusual and contrary to the critical
slowing down observed in the case of equilibrium phase transitions. We have
provided a possible explanation from the time evolution of the distribution of
the directions of velocities.
