Missing bugs spell trouble for birds

Inspect under the porch light at your home or vacation cottage and ask yourself: Are there as many moths and other insects hanging on the wall as there used to be?

Entomologists who have long collected insects in Europe recently reported that since the 1980s, flying insects have declined by 80%, confirming widespread observations of cleaner windshields on both sides of the Atlantic.

While people had noticed that populations of the charismatic monarch butterfly and honey bee crashed in the past decade, it wasn’t until last year that similar data were revealed on many other insect species from various locales.

Insects are the main food of most birds, and an 80 percent decline is massive – four out of five bugs gone. In fact, birds that catch bugs in the air, called “aerial insectivores,” have been declining faster than most other birds.

Swallows, swifts, flycatchers and relatives of the whip-poor-wills and nighthawks have been disappearing rapidly since the 1980s, by as much as 70 percent for some species in the northeastern U.S. and neighboring Canada. In Europe, the same phenomenon has been documented extensively for farmland birds. Because the types of birds that rely most heavily on flying bugs have been declining the fastest, it was not really a surprise to learn that the bugs are disappearing. One must also ask if our huge decline in bats, blamed entirely on the emerging “white nose” disease, has also been exacerbated by the loss of their sole food source.

But why? No one has the answer to this mystery yet.

One possibility is the widespread adoption of a new generation of pesticides, called neonicotinoids, that are extremely harmful to insect behaviors such as mating and homing. Another possible contributor is the advent of genetically modified soybeans, which are resistant to the herbicide Round-Up. The beans are sprayed heavily with the weed killer, eliminating all plants that bugs used to eat around farm fields and turning croplands into biological deserts.

Global climate change since the 1980s, such as shifting rainfall patterns and earlier spring warming, could be a factor. Perhaps an unknown disease is sweeping through insect populations, as is the case with chitrid fungus in global amphibians. Or has suburban sprawl finally crossed a tipping point, reducing available habitat below what is necessary to sustain insect populations?

Researchers will get to the bottom of this latest biodiversity scare soon, using the scientific method to generate unbiased facts that an educated citizenry can act upon.

Hopefully, we’ll figure it out before olive-sided flycatchers and whip-poor-wills decline past the point of no return. In the meantime, it is more important than ever to plant native vegetation on your property, favoring the native insects that birds feast upon. Consider leaving a portion of your yard messy, like the rough on a golf course, and you will be rewarded with a brighter thank-you display from the lightening bugs.

Cristol teaches in the Biology Department at the College of William and Mary and can be contacted at dacris@wm.edu. To discover local birding opportunities visit williamsburgbirdclub.org.

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