By Paul G. Wiegman, FOR THE PITTSBURGH TRIBUNE-REVIEW
The warm days of spring fill the air with -- I should write something lovely and enjoyable here, but I will be realistic -- bugs.
Let's face it, unlike the colder seasons, spring and summer are a time for insects. They crawl or hatch from moist soil, ponds, streams, behind bark and the underside of twigs to flit, flutter and fly through the delightful vernal air.
To some, flying insects are a necessary evil, but to others, they are breakfast, lunch, dinner and an anytime snack. Those others are insectivorous birds, and there are many.
Indeed, most of the birds that migrate into our region in the spring come here for the insects. Warblers, swifts, flycatchers, vireos, kinglets, gnatcatchers, thrushes, waxwings and swallows are all voracious insect feeders. Some of our year-round species change their diets in the spring. Titmice, chickadees and others give up seeds and turn to bugs.
Part of the delight of bird watching is observing the various ways in which birds feed on insects.
Warblers work the outer branches of trees when they are in flower. There the birds capture tiny insects as the bugs clamber over the blooms in search of their own meal. Flycatchers perch at the ends of limbs watching for larger flying insects passing by. When they spot a juicy fly, beetle or some other insect, they launch into the air and capture the bug on the wing. Chickadees, titmice, nuthatches and others look for insects crawling on the trunks of trees or hiding in bark crevices. They wander vertical surfaces to probe and poke recesses, pulling out soft caterpillars and beetle larva.
The most graceful of the avian insectivores are swallows and swifts.
Western Pennsylvania is the summer home to six breeding species of swallows. These include the tree, northern rough-winged, barn, cliff, and bank swallows and the purple martin.
Swallows are supreme fliers. Their long, pointed wings, forked tail and relatively short body give them an aerodynamic advantage for catching insects on the wing. They are often found in loose flocks swooping and diving over streams, rivers, ponds and lakes picking off insects emerging from the water.
I vividly remember spending spring evenings with the late Joe Grom, naturalist at North Park in Pittsburgh, sitting on a picnic bench at the edge of North Park Lake watching large migrating flocks of swallows. From that vantage point, we were often able to see all six Western Pennsylvania swallows in a single evening.
Of the six, the purple martin is the largest native swallow. They are famous for their communal roosts. For many years, there was a huge purple martin house in Somerset. The nest box was fashioned after the iconic Somerset County Courthouse near which it stood. Unfortunately, tropical storm Agnes in 1972, dumped torrential rain on the Laurel Highlands for a week. Rain is a problem for flying insects, and very few were in the air for seven days.
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