Whether you love or despise bugs, they’re important to birds (and humans). We’ll broaden your appreciation for Bugs in this and upcoming blogs.

The inter-relationship between Bugs and Birds is important in many ways. Some examples: Bugs are bird food. Over half of global bird species rely on bugs as their majority food source, and some rely on them almost completely. Bugs are pollinators. Insect pollination is required to produce fruit and seed for birds’ plant diets. Birds control bugs. Globally, birds eat the equivalent in bugs to the weight of meat and fish consumed by humans!

While some of us are enamored by bugs, human emotions also include fear and hatred. Most bugs, however, are misunderstood and pose no threat to us. So let’s learn more to better appreciate their benefit to birds and ourselves.

Carolina Chickadee carrying crane fly to nestlings
Carolina Chickadee carrying crane fly to nestlings

Photo by Karen Campbell

Bug numbers

“If variety is indeed the spice of life, then insects are the spiciest creatures on earth.” That is the opening introduction to the Field Guide to Insects of North America by birder extraordinaire Kenn Kaufman. In the US, there are nearly 91,000 insects and 4,000 spider species that are described, and an additional 73,000 undescribed. That’s over 100 times more known bug species than birds and it is likely 170 times or more!

“Bug” is a generic word with many definitions. I’m using it to define the Arthropods, invertebrate animals that include insects, spiders, and crustaceans.

The sheer number of bug species, combined with their small size, diversity, and multiple life stages make it challenging to identify most bugs to species in the field or by photos. Identification to a family or genus is often a tremendous success and often requires experts (try BugGuide.net or iNaturalist). As a birder, I expected to put a name to every bug at first, but I’m over that. Bug observation is fascinating anyway, and it’s so easy to get new lifers!

Red-winged Blackbird eating mayflies

Photo by Will Hilscher

Bugs as Bird Food

While birding, we observe bird behavior as they hunt for bugs. Songbirds leaf glean at the tops of trees during migration. Swallows and swifts catch flying insects on wing over fields. Ground feeders toss leaves and debris in their search. Woodpeckers excavate bark. Shorebirds probe vegetation and mud along the edge of ponds and streams. But we rarely see what the bird has captured, let alone identify it. Scientifically, birds’ bug diets are challenging to research. Much of what is known is by collecting birds and inventorying their stomach contents.

Bugs are especially important as a food source for nestlings. One recent study estimated that a brood of Carolina chickadees will be fed over 5,000 bugs while in the nest. (The same study showed that chickadees become food-limited if the surrounding biomass is < 70% native plants.) The insect orders most frequently fed to nestlings are flies, bees/ wasps, moths/ butterflies, grasshoppers/ katydids, beetles, and true bugs.

Have you seen a bird with a green “worm” in its bill? The insect larval stages make up the most significant part of nestling diets. They are easily digestible, have high protein content, and are easier for adults to find with less effort. Nestling birds receive necessary water for survival through their bug diet.

In future blog posts we’ll instill an appreciation of bugs and further cover their relationships with birds.

Karen Campbell, a member of Lehigh Valley Audubon and FocusOnNatives.com provided the content for this article.