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Living Sanibel: The common grackle

By Staff | Dec 17, 2014

Common Grackle

The grackle is one of the most common birds found in southwest Florida. Like the starling, house sparrow, and its cousin the boat-tailed grackle, the common grackle is most often found in and around parking lots, Dumpsters, and similar urban or suburban settings. Readily identified by several telltale signs, the common grackle is an easy bird to add to your wildlife list.

One of those signs is the bird’s distinct call: a short, high-pitched squeak that sounds like a metal gate in desperate need of oil. Other identifiable details are the pale yellow eyes and the oil-slick coloration, especially on the male. The grackle is easy to distinguish from the similar-size starling by the color of its bill-the grackle’s bill is solid black, whereas the starling has a long, pointed yellow bill.

The common grackle engages in an odd behavior called anting. It allows ants to crawl all over its body or sometimes catches them, squishes them in its beak, then rubs them all over its feathers in a practice believed to reduce parasites. The common grackle will sometimes resort to lemons or mothballs when it cannot find the ant-based formic acid.

The grackle is an opportunistic feeder. It eats insects, mice, seeds, berries, and garbage and has been observed wading into the water to catch minnows. For the most part the grackle is monogamous, but some males are known to be polygamous. It nests in colonies with other blackbirds. Large flocks sometimes cause problems in agricultural areas.

Boat-tailed Grackle

Similar to but quite a bit larger than the common grackle, the boat-tailed grackle is not quite as common as its close cousin. Easy to recognize by its unusually long, keel-shaped tail, the boat-tailed grackle is Florida’s largest blackbird.

The female of this species is much browner in color and slightly smaller than the male.

The boat-tailed grackle is one of the few birds that are not monogamous, and it has developed an unusual mating system similar to that of American elk and other ungulates. A single bird becomes the dominant male and defends his personal harem in a form of avian polygamy. Although the dominant male may get almost 90 percent of the copulations in his harem, we now know, thanks to modern DNA testing, that he actually sires only 25 to 30 percent of the offspring. The female grackle steps out repeatedly on the male while off foraging for food. This behavior helps to keep the gene pool far more diverse than it would first appear.

Like the other blackbirds, the boat-tailed grackle is an opportunistic feeder. It eats small fish, snails, aquatic and terrestrial insects, small birds, bird and reptile eggs, berries, grains, and seeds.

This is an excerpt from Living Sanibel – A Nature Guide to Sanibel & Captiva Islands by Charles Sobczak. The book is available at all the Island bookstores, Baileys, Jerry’s and your favorite online sites.