The deeper connections get stranger and more specific. Birds weave spider and insect silk into their nests, and some place those nests near stinging insects such as wasps for added protection — a living security system. More than 200 bird species rub crushed ants into their feathers as part of grooming. The ants likely release chemicals that deter parasites, essentially serving as a natural pesticide. Many vertebrates time their breeding seasons to match peaks in insect abundance, so their young hatch when food is plentiful.

The housekeeping services stretch back millions of years. Insects once lived inside dinosaur nests, cleaning them out, according to Grames. The same service continues today in the nests of some owls and kingfishers.

The project began in 2022 with the creation of the National Science Foundation–funded Status of Insects: An International Research Coordination Network. That network grew directly out of Grames' doctoral work in Elphick's lab.

Declining insects, declining vertebrates

Despite all this, few scientific studies have considered what declining insect populations mean for vertebrates — beyond a simple reduction in food supply. That blind spot worries the authors, because some insect populations have dropped sharply in recent decades, and the consequences will ripple outward to the animals that depend on them.

"We're losing insects at a rate of about 1% to 2% per year," Grames said. "When you scale that up across a few decades, we're talking about a major change to ecosystems. Insect conservation should be a top priority for anyone worried about the future of biodiversity."

A loss of 1% to 2% per year may sound modest. Compounded over 30 years, it implies a dramatically smaller insect population — and with it, fewer nest-building materials for birds, fewer cleaning crews in nests, fewer moths tending sloth fur, and fewer natural pharmacies for wound care.

Bridging two scientific worlds

The authors argue that effective conservation requires understanding these diverse roles, and that means breaking down barriers between disciplines. Elphick, an ornithologist by training, hopes the review will push scientists who study vertebrates to work more closely with those who study insects.

"If you want to have vertebrates, then you've got to be thinking about insect conservation, and we don't do that nearly enough," he said.

The review itself models that collaboration. With authors from eight countries spanning entomology, ornithology and ecology, it treats insects not as a separate conservation concern but as infrastructure for vertebrate life. Protecting a bird, in this framing, means protecting the wasps near its nest, the ants in its feathers and the silk in its walls.

As the paper makes clear, much of the evidence on these relationships remains scattered across decades of individual studies. Consolidating it is a first step. The next one — measuring how fast these connections break as insects decline — is a task the authors hope more researchers will now take up.