Jan Bergstrom, Birding

It has been an incredibly wet spring and early summer. The torrential downpours have resulted not only in a flood of water, but a flood of insects.

The relationship between birds and insects is interesting. The Minnesota Department of Natural Resources reported in June that loons were abandoning nests due to the incredible numbers of black flies that were feeding on them as they incubated their eggs. Black flies need moving water, of which there's been plenty, in which to lay their eggs.

Other birds are likely suffering as well. People often think birds, with their stiff coating of feathers, are not bothered by biting insects. These feathers provide some protection, but many parts of a bird's body, such as the head and ventral area, are covered with smaller, less dense, and more easily penetrable feathers. Featherless babies or those covered with down are especially vulnerable.

Black flies are not the only insects causing problems for birds this year. Many other biting insects are also having a banner year. The mosquito population is exploding and will stress the birds by feeding on them. They will also likely increase the number of deaths from West Nile disease, which can affect all birds, but especially those of the Corvidae (crows, jays, ravens and magpies) family.

Higher insect populations also lead to the deaths of birds indirectly through increased use of pesticides.

A study, "Worldwide Integrated Assessment of the Impact of Systemic Pesticides on Biodiversity and Ecosystems," published in June in a peer-reviewed scientific journal collected data from 150 published studies. It found neonicotinoids, which act as a nerve toxin to animals and are suspected in the decline of honeybees, are also responsible for the deaths of birds and other animal species.

Another pesticide, DDT, has been banned in the United States but is still manufactured here for use in countries where it has not been banned. This includes habitat for many of our neotropical migrants such as scarlet tanagers and Baltimore orioles. Worldwide, pesticide use is increasing.

Interestingly, pesticide use could be reduced if bird populations were encouraged. Birds are nature's pesticide and crucial in controlling normal insect populations. Intensified agricultural practices have eliminated the woodlots that were often found adjacent to fields. With this loss of habitat, birds disappeared, creating the need for more and more pesticides to deal with the insects that inevitably feed on the crops.

When there is an explosion in the population of a particular insect, birds usually do not have an effect on the excess numbers unless the explosion lasts for more than one year. The first year will provide more food for the birds' young, likely resulting in a higher survival rate for the fledglings. The following year, there will likely be more birds to reproduce, so if there is still an overpopulation of insects, these first-year birds will likely have a higher success rate in their own breeding. This can continue as long as the insect population increases, but may result in a decline in the bird population when the insect population returns to normal.

An exception to this lack of effect in first year increases occurred in Utah in 1858, according to folklore and historical accounts. When Brigham Young led the first Mormon settlers to Salt Lake City, they had a mild first winter, followed by an unlucky May in which hordes of mouse-sized, flightless katydids descended on their crops. They ate everything in their path, including other katydids. No matter how many were killed, more kept coming. The settlers prayed for intervention.

In June, a large influx of California gulls arrived and gorged on the katydids. They ate so many that when they would drink water, they would regurgitate, emptying their stomachs and then eating even more. Enough of the settlers' crops were saved to allow them to survive. From then on, the katydids were known as "Mormon crickets" and the California gull became the state bird.

Birds can also be affected by the lack of insects. In the Northeast, the number of aerial insectivores is crashing. The common nighthawk, purple martins, chimney swifts, flycatchers and other flying insect-eaters are disappearing.

These birds feed on the large numbers of insects and other invertebrates found in the sky, some of them as high as airplane-cruising altitude. The aerial insect population is plummeting due to climate change, severe storms, pollution and other factors. As the insect population plummets, so do the bird populations.

You can see the relationship between birds and insects is constantly changing. Birds tend to benefit from insect population explosions. In a year such as this, however, the easy food supply comes with a price — stress due to harassment by biting insects.

This is the opinion of Jan Bergstrom, whose column appears the first Sunday of each month in Our Woods & Waters. She welcomes questions and comments at janbergstrom2@gmail.com.