Oaks support more life-forms than any other North American tree genus, providing food, protection or both for birds to bears, as well as countless insects and spiders... With 90-plus North American species and about 435 worldwide, Quercus is the Northern Hemisphere’s largest tree genus, made up mostly of trees that are very large and very long-lived, two factors among several that help explain the oak’s power...Oak trees support 897 caterpillar species in the United States. At Mr. Tallamy’s 10-acre property in southeastern Pennsylvania, he has recorded 511 — dwarfing the number supported by other native trees there... [but not many butterflies, AFAIK: Hairstreaks, Red-spotted Purples, and Duskywings.]An oak can produce three million acorns in its lifetime — tons of protein, fat and carbohydrates — and a mature tree can drop as many as 700,000 leaves every year.. The resulting litter is habitat for beneficial organisms...Oaks and jays evolved together about 60 million years ago, in what is now Southeast Asia. Jays grew so adapted to life alongside oaks that a small hook at the tip of their bill “is designed to rip open an acorn husk,” Mr. Tallamy writes. The bird’s expanded esophagus (a gular pouch) can hold up to five acorns — each one buried in a different spot.
I didn't know about the mutualism of blue jays and oaks. You learn something every day.