I am always impressed with our small birds. Of course, the ruby-throated hummingbird is far and away the champion among our tiniest, but we have a number of others that aren’t too much larger.

For a weight comparison, consider a pat of butter – what you get when you scrape that sixth of an ounce out of its foil cover. A robin weighs in at more than 16 of those pats; a bluebird, more than 6 pats; a house wren or chickadee, 2.3 pats; a kinglet or gnatcatcher, 1.3 pats; and a hummingbird, .7 pats. Just imagine, that feisty little hummingbird that beats its wings at a spectacular 20 to 30 times per second weighs only two-thirds as much as a pat of butter.

On that list of diminutive characters is one of my favorite birds: the blue-gray gnatcatcher. It partly makes up in name-length what it lacks in weight. To identify one, simply look for a small, slim bird, gray above and white below, with a long and constantly flitting black and white tail. Or, if you know what a mockingbird looks like, shrink its dimensions in half, take away the white patches in the wings and you will have a gnatcatcher.

I don’t see gnatcatchers all that often because they generally remain high in trees. They are most often located by their distinctive call notes. Francis Weston, who wrote the Bent Life History of this species, describes those notes as “scarcely louder than a whisper.” Those thin buzzing calls with many spee-like sounds are too high for my aging ears to pick up. I did, however, find two recently along the Swallow Hollow Nature Trail off Knowlesville Road in the Iroquois National Wildlife Refuge. They were flitting about the branches of a cottonwood next to the boardwalk about a hundred yards south of the main trail entrance.

They are great fun to watch. Weston tells us, “The gnatcatcher is a little bird of intense activity; active, not with the methodical continuity of the brown creeper, but with an irrepressible vivacity of its own in all phases of its life cycle – feeding, nesting, care of its young – at all times, in fact, except during the enforced inertia of incubation.”

Like chickadees, nuthatches, kinglets and creepers, gnatcatchers feed on the tiny insects they find in their constant search of tree limbs and leaves. But gnatcatchers don’t deviate from this diet. While those other species will take seeds from your feeders, gnatcatchers stick exclusively to arthropods. Thus they are very beneficial birds.

Although they do not overwinter here, they appear among the early passerine migrants each year, arriving in mid-April. After a week or two of courtship, each pair builds a new nest. I say new because, if there is one left over from the previous year, they won’t use it but will instead tear it apart and reuse the materials.

I’ve seen only one gnatcatcher nest and it certainly impressed me. It was a slightly larger version of a hummingbird nest. Hold the tip of your index finger against the end of your thumb and those fingers would have enclosed its approximate area. It was really small.

Located on top of a horizontal limb about 20 feet high, it was beautifully constructed: gray, cup-shaped and compact. The materials they use to make their nests include plant down and fiber, lichens, oak catkins, feathers and bark. All of these ingredients are held together by spider web and insect silk, like that of the tent caterpillar.

Gnatcatchers’ four to five eggs are scarcely larger than peas. They are pale blue with reddish-brown spots. Unfortunately, they are far too often victimized by cowbirds. One observer found 83 percent of their nests stuffed with cowbird eggs or young. The results are inevitable: tiny gnatcatchers feeding greedy immature cowbirds more than twice their size, their own offspring unable to compete. This may be the major reason why gnatcatchers are so uncommon.