We obtain the Page curves of an eternal Reissner-Nordstr\”om black hole in
the presence of higher derivative terms in four dimensions. We consider two
cases: gravitational action with general ${\cal O}(R^2)$ terms plus Maxwell
term and Einstein-Gauss-Bonnet gravity plus Maxwell term. In both the cases
entanglement entropy of the Hawking radiation in the absence of island surface
is increasing linearly with time. After including contribution from the island
surface, we find that after the Page time, entanglement entropy of the Hawking
radiation in both the cases reaches a constant value which is the twice of the
Bekenstein-Hawking entropy of the black hole and we obtain the Page curves. We
find that Page curves appear at later or earlier time when the Gauss-Bonnet
coupling increases or decreases. Further, scrambling time of
Reissner-Nordstr\”om is increasing or decreasing depending upon whether the
correction term (coming from ${\cal O}(R^2)$ terms in the gravitational action)
is increasing or decreasing in the first case whereas scrambling time remains
unaffected in the second case (Einstein-Gauss-Bonnet gravity case). As a
consistency check, in the limit of vanishing GB coupling we obtain the Page
curve of the Reissner-Nordstr\”om black hole obtained in arXiv:2101.06867.
