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Easygoing Grackles Say 'Spring'

April 07, 2009 - Chances are good that common grackles have returned to your neighborhood by now. These large members of the blackbird family are one of the first of our migratory breeding birds to come back to Maine.

With a sleek, glossy black plumage and a yellow eye, the adult common grackle is a striking bird. The birds are about 12 inches long, including the long tail. It is not easy to tell males from females although the male, in favorable light, has a glossy purple head and breast. The female is usually slightly smaller than the male. In flight, grackles hold their tails in a V, like the keel of a boat.

Despite their sleek appearance, grackles will win no contests for the beauty of their songs. Both males and females sing the same harsh, squeaky song that some ornithologists interpret as "squ-eek", "readle-eak" or "scuda-leek." Some people think the song sounds like the opening of a gate with a rusty hinge. These birds also give a characteristic raspy "chack" call, often in flight.

Males sing more frequently than females and male song rates are highest early in the breeding season. Any individual sings a single song but there is a lot of variation among individuals. The songs therefore seem to be useful for individual identification.

Grackles are habitat generalists. Suburban areas, farmlands, swamps, and orchards are all suitable. Favoring more open habitats, grackles are typically not found in deep forests. Before European settlement and the clearing of forests, common grackles were uncommon birds in New England; now they are abundant. Aided by the planting of shelterbelts, common grackles have expanded their range westward across the Great Plains.

This species is highly gregarious; if you see one, you will probably see 10. Except for females incubating eggs, grackles roost together at night in noisy roosts, sometimes more than 100 birds in one roost.

Unlike some of our long-distance migrants, common grackles do not winter very far to the south of us. Some winter in southern New England with more wintering from Pennsylvania south.

Once the grackles return, keep an eye out for their courtship displays. The male will raise the feathers around his neck, drop his wings and sing his song for a prospective mate. This behavior is called the song spread.

Pairs form soon after the birds arrive. The female builds the nest, usually well above the ground in a conifer. The male guards the female throughout the nest construction process. Once the nest is complete, the female will perform a wing quivering display, a signal that she is ready to mate.

The male aggressively keeps other males away from his mate. A common threat display is sky pointing, when the male raises his bill vertically. This behavior is given by one male on the approach of another male. The display usually results in one of the males departing.

Common grackles may nest alone but more often in colonies of 10 or more pairs in tall trees, especially evergreens. Sometimes, nests are made in freshwater marshes, old buildings and even the lower parts of osprey nests. The nest is made of twigs and grass stems. Most nests contain five to six eggs, which the female incubates for about 14 days before the eggs hatch. Newly hatched birds are ready for their first flight in 14-16 days. Unlike their dark parents, juveniles are dark brown with brown eyes.

Grackles have a broad diet, although insects are the most commonly captured prey. Grackles often search for food on the ground, walking slowly and deliberately. Occasionally, a bird may run and leap into the air to catch an insect. Grackles may probe in the ground for earthworms and will even take them from robins. Grackles will also search for food in trees.

Besides insects, grackles are known to eat spiders, snakes, lizards and mice. The eggs and nestlings of other birds are not safe from grackles. Grackles are even reported to wade belly deep in freshwater for crayfish, minnows, frogs and salamanders. Grackles will eat seeds including corn, acorns and seeds of various weeds. In fact, common grackles are now a major agricultural pest, causing millions of dollars of damage to sprouting corn.

Some common grackles attain impressive ages. The oldest known common grackle was banded in Michigan and recaptured 20 years and 11 months later in Illinois! A common grackle in Minnesota lived to be at least 17 years old, while a New Jersey bird lived to be at least 16 years and 1 month old. The average life span is likely much less than these extremes.

HERB WILSON, Portland Press Herald, April 2, 2009


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