  We examine the feasibility of deriving neutrino mixing parameters $\delta$
and $\theta_{13}$ from the cosmic neutrino flavor composition under the
assumption that the flavor ratios of the cosmic neutrinos at the source were
$F_{\nu_e}+F_{\bar{\nu}_e}:F_{\nu_\mu}+F_{\bar{\nu}_\mu}:
F_{\nu_\tau}+F_{\bar{\nu}_\tau}=1:2:0$. We analyze various uncertainties that
enter the derivation of $\delta$ and $\theta_{13}$ from the ratio of the
shower-like to $\mu$-tracks events which is the only realistic source of
information on the flavor composition at neutrino telescopes such as ICECUBE.
We then examine to what extent the deviation of the initial flavor ratio from
$1:2:0$ can be tested by measurement of this ratio at neutrino telescopes
taking into account various sources of uncertainty.
