In the coniferous forests of oregon, eight species of woodpeckers coexist. four species select their nesting sites based on tree diameter, while the fifth species nests only in fir trees that have been dead for at least 10 years. the sixth species also nests in fir trees, but only in live or recently dead trees. the two remaining species nest in pine trees, but each selects trees of different sizes. this pattern is an example of
(a) resource partitioning.
(b) commensalism.
(c) predation.
(d) predator-mediated competition.
(e) a keystone species.