  A version of the second main theorem of Nevanlinna theory is proved, where
the ramification term is replaced by a term depending on a certain composition
operator of a meromorphic function of small hyper-order. As a corollary of this
result it is shown that if three distinct values of a meromorphic function f of
hyper-order less than 1/n^2 have forward invariant pre-images with respect to a
fixed branch of the algebraic function t(z)=z+a_{n-1} z^{1-1/n}+...+a_1
z^{1/n}+a_0 with constant coefficients, then f(t(z)) = f(z) for all z. This is
a generalization of Picard's theorem for meromorphic functions of small
hyper-order, since the (empty) pre-images of the usual Picard exceptional
values are special cases of forward invariant pre-images.
