World Migratory Bird Day highlights the link between birds and insects

The naturalist E.O. Wilson is said to have affectionately called insects “the little things that run the world” because they, despite their tiny sizes, play an outsized role in making many of Earth's natural processes happen. Insects are pollinators, pest control, decomposers, and crucial links in the food chain. Without insects, our world would be a very different and (likely less hospitable) place. 

Birds themselves run on these “little things that run the world.” An astonishing 96 percent of all terrestrial North American bird species rely on insects for at least part of their diets at some point throughout the life cycle. They are especially important for young migratory birds: a steady diet of protein-rich insects like caterpillars helps them grow quickly and fuel up for migration. 

May 11, 2024 is World Migratory Bird Day in the Americas, a day of celebration and awareness that comes at the height of spring migration as millions of birds make their way north to their breeding grounds. This year's World Migratory Bird Day theme, Insects, is a nod to the vitally important roles of bees, butterflies, caterpillars, caddisflies, and others, not only for birds but for people, too. 

Unfortunately, insects are in a state of freefall. Species diversity, abundance, and biomass (the measurement of the weight of organisms in a given area or by volume) are all declining. While much attention is focused on the decline of honey bees and Monarch butterflies, insect species across the board are struggling. And if insects are struggling, the birds that rely on them are, too. 

While nearly all birds in North America will eat insects at some point, some are more reliant on them than others. As their name suggests, the group of birds known as aerial insectivores have a diet that is heavy on insects, most of which they catch on the wing. And it's safe to assume that amid an insect freefall, aerial insectivores like the Common Nighthawk have taken a nosedive. The loss of their primary food source has hit this group of flycatchers, swallows, nightjars, and others, acutely: since 1970, 160 million aerial insectivores have been lost, accounting for a 32 percent reduction in their population. 

The conditions that are leading to insect declines are also affecting birds both directly and indirectly. Habitat loss is the main culprit: without quality habitat, neither birds nor insects can thrive. Pesticide use unleashes harmful chemicals into the environment that destroy plants and insects and can poison birds. In both cases, the challenges can be compounded for birds, who suffer not only from the direct effects but from the secondary effects of the loss of their food sources, as well. 

Just as many of the challenges facing insects are also facing birds, many of the positive actions we take to help either group will benefit both. What's good for insects is also good for birds! Here are some actions to get started.

Pass on Using Pesticides

While there are multiple factors contributing to the alarming drop in insect populations, one stands out: pesticides. The pesticides we use don't discriminate: though the target might be an unwelcome aphid infestation in farm fields or an unpleasant swarm of mosquitoes in the backyard, those aren't the only creatures encountering pesticides. 

Even when pesticide use is localized, its effects can be far reaching. Among the most insidious pesticides are neonicotinoids, or “neonics.” American Bird Conservancy (ABC) has been documenting the rise of neonics and advocating for stricter regulation of these extremely dangerous chemicals. 

Though initially created for controlling sap-sucking and leaf-eating pests in large-scale agricultural settings, neonics have worked their way into products commonly used around cities, schools, and homes. Long-lasting and water-soluble, neonicotinoids can be dispersed far beyond their intended targets, carried on the wind as spray drift or dust particles, or enter the water system through runoff or leaching into groundwater. Plants can take up the chemicals into leaves, pollen, and nectar, which can be consumed by insects and other animals. A majority of native bee species nest in the ground, leaving them vulnerable to neonics that enter the soil. Neonics are so toxic that a single seed coated in the chemical can kill a songbird. Though they have been banned in the European Union, neonicotinoids are significantly less regulated in the United States. 

Birds aren't always directly encountering the effects of pesticides. Often, the harm done to birds by pesticides comes second-hand. Over time, birds of prey can fall ill or die due to ingesting mice, rats, and other wildlife which have consumed rodenticides. Adult birds might feed insects that have come into contact with pesticides to their nestlings. Eventually, the loss of insects due to pesticides affects birds, impacting their ability to find food.

Here's how you can help address the problem of pesticides:

• Avoid using synthetic pesticides of any kind whenever possible (this includes rodenticides, herbicides, fungicides, and more). Instead, opt for organic or chemical-free methods for pest control. 
• Choose produce that is grown organically when possible. Organic growing practices do not employ the kinds of harmful pesticides that can negatively affect insects and birds. 
• Join ABC in advocating for policies that strengthen laws regulating pesticides and support the ability of local communities to determine how and what pesticides will be used where they live. 
• Learn more about the link between neonicotinoids and bird declines in an ABC webinar. 

Invite Beneficial/Native Insects into Your Garden

We often are told to grow native plants in our gardens because they benefit birds, and that's true: native plants in their own right provide the shelter, nesting sites, and much of the food birds need. But the insects they attract are the icing on the cake for birds! Birds' arrival on their breeding grounds is strongly linked to the availability of their preferred food sources. 

A majority of North America's insects have diets so specialized their mouths are actually designed to eat certain plants! These insects are often eaten by birds who also have particular tastes, adaptations, and nutritional needs. Native oak tree species support more than 900 moths and butterflies in the family Lepidoptera. Their caterpillars are the nutritious staple chosen by many bird parents for their nestlings (and the parents themselves often partake, too.) Caterpillars make up two-thirds of the diets of many wood warblers, like the Near Threatened Golden-winged Warbler. Scientists have observed that a single pair of nesting chickadees fed as many as 9,000 protein-packed caterpillars to their brood. 

Many insects have such specialized diets that they are named for the plants that nourish them. While the Jack Pine Budworm is considered a pest with the capacity to wipe out the trees if left unchecked, to the Kirtland's Warbler, the larvae of these moths are a necessity. Their taste for budworms helps keep the insects from doing damage to trees, and the insects fuel the chicks' development, preparing them for their first journeys south at the end of the breeding season.

There are many ways to provide the native plants birds and insects need:

• Learn about the plants native to your area and incorporate them into your landscape. You don't need to grow oaks in your yard to help insects and birds. There are a variety of plants, from shrubs to perennial flowers, that can provide food for insects. Native milkweed species are vital for Monarch butterflies and they're likely to attract other insects that birds love to eat. Spicebush berries are beloved by birds from Wood Thrush to Eastern Bluebirds. They're also the host plant for the beautiful Spicebush Swallowtail butterfly — their larvae make an excellent snack for bluebirds. 
• Maximize the space you have. Even small areas can make a big difference for insects and birds. If you lack the space to grow a full garden, window boxes or planters with native plants like bee balm can be a pitstop for hummingbirds and other species. 
• If your yard is looking messy, “leaf” it alone: those layers of leaves are a nursery for moths, fireflies, beetles, and other insects, and provide protection from predators. Bonus: The leaves also act as fertilizer for your yard as they break down. Discover other tips for keeping your backyard habitat bird-friendly year-round.
• Get inspiration for your garden from ABC staff!

Support Policies and Initiatives that Bring Back Habitat

As is often the case when talking about birds, it all comes back to habitat. The loss and degradation of important habitat for insects — which is often important for birds, too — is one of the largest drivers of plummeting insect populations. Without suitable habitat, insects simply cannot survive. 

Migratory birds are doubly impacted by habitat loss and the associated decline of insect availability. Habitat loss from overgrazing, agriculture, and development has taken a heavy toll on their nonbreeding grounds in Central and South America, their breeding territory in North America, and at stopover points in between.

In the Southwestern U.S., riparian zones (forested areas along streams and rivers) in desert landscapes have been heavily developed and are disappearing quickly. That spells trouble for the Southwestern Willow Flycatcher, which has lost 90 percent of its range. For species that are feeling the pressure of habitat loss, the loss of food sources is felt even more acutely.

Help maintain and restore habitats for birds and insects:

• Minimize habitat destruction on your own property when undertaking projects. Every shovelful of dirt contains an ecosystem. Consider your potential impact. 
• Support the habitat management and restoration efforts taking place in your own community.
• Advocate for a strong Farm Bill. This piece of legislation is the single largest annual source of conservation funding in the world. The Farm Bill, passed every five years, supports the restoration of grasslands and includes incentives for farmers to operate with conservation in mind. Restoring grasslands benefits insects and some of North America's most imperiled and quickly declining bird species.
• Turn off the lights at night. Many of us don't think about the sky as habitat, but for birds and many insects, what happens mid-flight is just as important as what happens on the ground. Birds and many insects are negatively affected by bright, artificial lights. Those lights can lure birds off their migratory routes and result in window collisions, and they can disrupt the natural behaviors of insects like fireflies and moths and even lead to mortality.

Appreciate the Little Things That Run the World

They may be creepy and crawly, but insects are essential to our existence. They provide the ecosystem services that we rely on every day, often without realizing it: decomposing organic matter and reducing the spread of disease, pollinating plants that grow into the food we eat, and so much more. They also allow birds to flourish, another essential service for those of us who care about them! 

Learning more about insects and their relationships to the plants around us and the birds we love can deepen our appreciation for the intricate webs of life within ecosystems. It can also encourage us to see ourselves in that same ecosystem, fulfilling a role that, if we take the right steps, can be beneficial for insects and birds.