Rivers Merge [Free Verse]

Rivers merge.

Trees may fork,
but rivers merge.

True, sometimes rivers split
to form an island,
and when they near the sea
they may branch out 
like the roots of a tree.

How the river knows 
it's near the sea
is unclear to me,
but it is the river's nature.

As is the tendency 
of rivers to merge
toward unity of flow.

But what is my nature?