Is a oak tree a heterotroph?

Okay, first of all, the Words "oak" and "omnivore" both start with vowels, so there should be "an" before them, not "a." Second, an omnivore can only be a secondary consumer, which eats primary consumers, which eats producers. Oak trees are producers, so their acorns are eaten by squirrels, which are primary consumers, which are eaten by foxes and stuff.