A female House Sparrow feeding beetle larvae to fledgling. Photo: Maurice Baker

When seeing a spider in a house, most people instantly kill it or move it away, even though spiders eat many of the harmful bugs in our environment. The same is true for insectivorous birds that control harmful pests.

These bug-eating species are more crucial to the natural ecosystem than people may think.

In the study, researchers revealed that birds consume 400 to 500 million metric tons of bugs such as beetles, flies, ants, moths, aphids, grasshoppers, crickets and other insects annually on a global scale.

And it is noted that this is the lower end of the range as these estimates are based on 103 experimental studies from around the world.

The amount consumed by the birds equals as much energy as a megacity, Martin Nyffeler, of the University of Basel in Switzerland, explained.

The study detailing these findings, "Insectivorous birds consume an estimated 400-500 million tons of prey annually," was published in Science of Natural, Vol. 1.

Prime time for protein

The insectivorous’ bug-heavy diet, mostly during the insects’ breeding period when there is an influx of protein, is part of the natural suppression of harmful insects that protects forests, grasslands and other areas from being negatively impacted by the harmful insects.

During periods of insect breeding, 90 percent of the birds in temperate or colder climates rely on this protein for their diet while 60 percent of birds in tropical regions rely on the insects for protein during that period, according to the research.

This results in consuming large amounts of anthropods.

Encompassing 75 percent of the entire prey biomass, forest birds consume the highest number of anthropods compared to birds in other climates such as tropical grasslands, temperate grasslands, croplands, deserts and the arctic tundra.

“In forests, they have an ecological and economic impact by destroying countless forest pests—in particular, lepidopteran larvae (butterfly and mouth caterpillars)—that they feed to their young,” Nyffeler said in a statement to Laboratory Equipment. “Especially in situations where forest pest densities are low, birds help to suppress potentially harmful insect species below damaging levels.”

The harmful insects that these forest birds eat consist of the gypsy moth, western spruce budworm, oak leafroller moth and other bark beetles, the researchers stated.

Natural suppressor for the ecosystem

Control of these harmful insects not only influences the ecosystem itself, it also has an influence on tropical plantations.

Reports suggest that in tropical coffee plantations located in areas such as Costa Rica, Guatemala, Jamaica and other areas where coffee is grown birds aid in the suppression of agricultural pests. And the birds successfully suppress the most damaging insect pests in the coffee plantation.

But birds cannot accomplish this suppression alone.

Spiders and other beneficial bugs also play a key role in suppressing harmful bugs from affecting these environments.

“To summarize all of this, birds in concert with other natural enemies (spiders, ants, insect parasitoids) make a contribution to insect pest suppression. If natural enemies provide pest suppression ecosystem services, less pesticides have to be used,” Nyffeler said in an email. “But birds alone don’t save the world. Likewise, spiders and ants don’t save the world.”

Shedding light on a declining species

This study was not done to engineer new ways of crop pest prevention, but to illustrate the importance of these declining bird species in the natural ecosystem.

Ultimately, their decline further threatens the natural ecosystem, and nature losses a protector.

According to the researchers, birds are now considered an endangered class of animal as they have been impacted by afforestation, agricultural efforts, pesticides, the threat of domestic cats, light pollution, climate change and more factors.  

“In a world without birds, man (homo sapiens) will find other solutions by applying more pesticides etc. The world will go on,” Nyfeller concluded. “But it will be a more ‘artificial world’ where the natural regulation mechanisms no longer function and are replaced by artificial solutions. It will be a poorer world when we no longer will hear the birds sing.”