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World Migratory Bird Day: Birds Need Bugs, And Both Need Our Help

By Sebastian Echeverri on 9. May 2024
Sebastian Echeverri

Insects and other invertebrates are an irreplaceable part of every ecosystem on Earth. When insects are in trouble, so is everyone else – as we can see clearly from the struggles facing many birds. In the past 50 years, bird populations in North America have dropped by over 3 billion individuals. Almost all of these losses come from species that feed on insects, mirroring the ongoing declines of those insects themselves. While that can sound bleak, it is also an opportunity: by conserving insects, we can make a difference for many more animals too!

The interconnectedness of insects and birds is at the core of this year’s World Migratory Bird Day, and the Xerces Society is proud to be a partner with this movement to protect bugs and birds alike. While plenty of non-migratory birds also rely on insects for food, those species that do undertake long journeys every year are especially impacted when bugs are scarce. Whether enough insects are available can determine the timing, duration, and overall success of bird migrations.

With many in-person and virtual events in the lead up to World Migratory Bird Day on May 11th, there are plenty of opportunities to learn more about both of these groups of animals, and how we can protect them. 
 

"World Migratory Bird Day. Protect Insects, Protect Birds" Illustrations of many different birds and insects
Bird migration is a natural phenomenon that has captured the imagination of people across cultures for centuries. Yet, the very phenomenon of bird migration is under threat, particularly due to declining insect populations, upon which many migratory birds rely for sustenance. (Photo: Anna Rose for World Migratory Bird Day)

 

Many birds rely on bugs for food during the most important parts of their lives

Insects, arachnids, and other bugs are a critical part of the diets of many birds. Bugs are full of remarkable nutrients, providing birds with protein-dense, high-energy sources of food. Some birds such as warblers, flycatchers, swallows, and swifts, feed on insects for most of their lives. However, many birds that we might not think of as insect-eaters rely on insects during migration and at other important stages in their lifecycle, in particular for raising their young before they are able to fly.

For example, consider the  broad-tailed hummingbird (Selasphorus platycercus)! This species breeds in western North America and migrates south to Mexico and Central America. While their primary diet is nectar, which is low in protein, they supplement it by hunting insects in flight or perched on foliage between trees. A nesting female can capture up to 2,000 insects in a single day, a useful source of protein-rich food for raising chicks. They also hunt mosquitoes in the air or consume mites while feeding on nectar. 

 

A male broad-tailed hummingbird hovering in midair, showing his iridescent purple throat feathers
Male broad-tailed hummingbirds also rely on insects, focusing on hunting insect prey especially while defending their feeding territories in early summer, which is a very energy-intensive activity. (Photo:  Greg Schechter CC-BY 2.0)

 

Indeed, many of the birds we regularly see eating seeds from feeders secretly also need insects to survive! Seeds are fine for adult birds that have strong enough beaks to break them open, but baby birds often can’t eat them at all! During the nesting season, parents must catch insects and spiders for their chicks.

Contrary to what many people think, we often underestimate how much birds of prey rely on insects for their diet. The American kestrel (Falco sparverius) is a species found all over the world and loves soaring over fields to snatch insects from the air. It captures the big ones like grasshoppers, cicadas, beetles, dragonflies, butterflies and moths. 

Without an adequate supply of energy-rich insects, birds may struggle to complete their migrations. Insufficient nutrition can lead to weakened immune systems, reduced reproductive success, and increased mortality rates among both adult birds and their offspring.

 

A kestrel perched on a branch with a dragonfly in its beak.
About 82% of the kestrel’s diet is made up of insects, especially during breeding seasons or when they stop at certain points on their migratory routes. (Photo: USFWS Mountain-Prairie CC-BY 2.0)

 

Bird and bugs are facing the same threats

Where natural spaces, such as forests or grasslands, are transformed or destroyed by activities such as intensive agriculture or urban development, insect populations drop, often dramatically. Damage to a few key habitats can create a negative cascading effect that results in severe bird population declines, across the many species that share a migration route.

Likewise, pesticides often have dangerous consequence for wildlife. Many pesticides affect many different species, apart from their intended target. This can be either directly (by killing them) or indirectly (for example by polluting water bodies and affecting water invertebrates’ development). The use of chemicals in agricultural fields can dramatically decrease the population of kestrels and other birds that would otherwise control insect populations. And in our yards, pesticides can impact species like hummingbirds, and the insects they depend on for survival.
 

Together we can take action for birds and bugs

Why are we at Xerces so happy for birds to eat plenty of our favorite insects? While it can be sad or uncomfortable to see a bug you like get eaten, that interaction is also a part of nature. A healthy ecosystem can support enough bugs that while some are eaten by birds, plenty others survive and reproduce. Birds also help control the populations of the few insect species that can be problems for humans, such as mosquitoes and insects that can damage crops.

And many of the strange and wonderful things about bugs, such as the bold colors of monarch butterflies, the incredible jumps of grasshoppers, or the fascinating mass emergence of cicadas, have been shaped by evolving in response to predators like birds. They wouldn't be the bugs we know and love without that evolutionary history. 

Every action we take to save insects from pesticides, or to conserve nesting habitat for birds, helps the other. Together, bird watchers and bug fans can make a healthier world for everyone.

Here are ways you can stand up for these animals:

 

Authors

Dr. Sebastian Alejandro Echeverri, PhD (he/him) is your friendly neighborhood spider scientist, wildlife photographer, and science communicator. He joined Xerces in 2024 as a communications specialist for science and digital media, and is excited to continue making bugs (and bug conservation!) more accessible, inclusive, and joyful for everyone.

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