JUNE
2010

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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06-23-10

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Flying Insectivores on the Prowl in Summer


The insects around our place should be shuddering in their exoskeletons this time of year. That is because flying insectivores are busily engaged in living up to their name. Flying insectivores? These birds eat insects. They also feed insects to their young.

This is the season when bird nesting is in full swing, and the insect eaters of the feathered set are scouring the landscape for insect food. One of the rules of nature is that everything has to eat, and insects are good food items, especially for birds. It is a bird-eat-bug world out there! Such behavior is good for the birds and not so good for the insects. Of course if you don't like insects, this is a good thing.

Some of the bird insectivores are on-the-wing predators. This is the case with swallows. The barn swallows, which appropriately have constructed mud nests in the shelter of my barn, feed on insects 99 percent of the time. The same is true of a pair of tree swallows that have set up housekeeping in some birdhouse gourds suspended on a pole near the garden.

Purple martins are the largest of the swallows in North America, and those flying high overhead at our place devour all kinds of insects. Research in one study showed that the martin diet consisted of 35 percent bees and wasps, 26 percent flies and 18 percent beetles. The remainder of the martin diet included all kinds of other insects, even a few dragonflies.

Woodpeckers eat both the adult and immature insects that they extract from the wood by pecking holes. However, woodpeckers are happy to accept a handout of suet when provided by a bird-feeding enthusiast. A lot of woodpecker holes on a tree might be an unsettling indication that some pest insect, such as the emerald ash borer, is feeding below the bark.

Catbirds have a nest in a lilac bush at our place, and their diet consists of 60 percent insects, including aphids and caterpillars. Unfortunately the rest of the catbird diet is fruit, such as cherries and strawberries. Oh well, I guess you can say I owe some fruit to birds that have helped rid my garden plants of aphids.

The eastern phoebes that have a nest on the water downspout under the eaves of our house are also insect eaters.

Eastern phobe perched on a branch
Eastern Phoebe

Phoebes sometimes catch their insect prey from the wing but also fly up from a perch to snatch the insect from the air. The phoebe just happens to be the first species of bird banded by John James Audubon back in the 1800s.

The feisty little wren also consumes insects and spiders. The wren diet has been shown to consist of 98 percent arthropod prey, including bees, beetles, bugs, moths and spiders. One male wren once visited its nest 111 times in one hour to deliver insects to the open-mouthed brood residing there.
 
Both Baltimore orioles and eastern meadowlarks construct their nests of woven grass strands. The oriole nest is a hanging bag suspended high in a tree, and the eastern meadowlark nest is a covered affair, located at ground level and anchored to surrounding grasses. Both of these bird species are primarily insect consumers; they also eat a lot of caterpillars. The ground-dwelling meadowlark chows down on grasshoppers and crickets as well.

A few bird species take advantage of insect food when available. For example, the red-winged blackbirds depend on insects for food in the summer time but eat seeds and other vegetable matter the rest of the year. Bluebirds have a similar diet, consisting of 80 percent insects in the summer but fruits and berries at other times.

Some birds pick up insects when feeding on the ground. The familiar robin hops around on the ground and collects earthworms and insects in the morning hours but goes for fruits in the afternoon. In the case of ground-feeding pheasant and quail, the newly hatched chicks will catch and eat many insects. The adult birds of both species depend more heavily on grain but will not shun a tasty insect morsel.

Even the detested house sparrows and starlings consume a few insects. Both of these bird pests are likely to take advantage of insects as food for nestlings. The total diet of house sparrows and starlings though is less than 5 percent animal matter. However, both species of these birds have been known to occasionally catch and eat adults of the Japanese beetle. And that, to most gardeners, has got to be a good thing!

 

 

Writer: Tom Turpin
Editor: Olivia Maddox