Nature Notes: Indigo Bunting
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By Ed Robinson
Late April often finds me planting bare-root saplings at our old farm where we’re converting a hay field into prime wildlife habitat. On my knees scraping soil back into a hole I saw a flash of blue high in the nearby hedgerow. Was this a new floater in my aging eyes?
Turning my head I was treated to the sight of a beautiful indigo bunting. Undisturbed, he burst into song probably hoping to attract a female to what seemed like prime nesting habitat. Over and over the plump little bird broadcast his cheery song “sweet sweet chew chew sweet sweet” but no females responded. Eventually I had to move on to the next sapling and my visitor flew to another perch hoping for better luck.
The natural world is full of bright and beautiful creatures but the indigo bunting ranks right up there. During the breeding season from spring through summer the male thrills us with showy plumage that ranges from indigo blue on his head to a lighter color on the body sometimes referred to as cerulean blue. His short conical bill is dark on top and the bottom is silver-gray. His feet are black or gray. The genus name for the indigo bunting “passerina cyanea” is descriptive of the bird with cyanea being the Latin word for sea blue.
Typical of most bird species, the female is colored in shades of brown with lighter shades on her underparts. The wings have darker markings and her bill is light brown with a touch of blue. She may display a light patch on her neck and a touch of blue on her wings or rump but overall her coloring is intended as camouflage to protect her while she is nesting and caring for her brood.
In parts of their Eastern range, from Florida to southern Canada, bunting can be one of the most common songbirds and they are often visible along roadsides or forest edges. The birds favor brushy patches, fallow fields with thick cover, swamps and edges along rail or power lines. For this reason indigo buntings are more common in rural areas than in urban areas or regions with intense agriculture.
The birds forage on the ground and in shrubs or trees from spring into autumn. Their primary food is insects while they will gladly take berries of all kinds. In winter their primary food will be seeds and grains when available. Because the birds are territorial during breeding season they forage alone in summer but in winter they can be seen feeding in flocks.
Indigo bunting males establish breeding territories in April or May after completing their migration flights. Having picked a site the male defends it with frequent singing or a fluttering of wings if needed to ward off a rival. Once a female responds to the male’s calls and mating occurs, the female chooses her nest site. She favors thick bushes or low dense trees for security. Often using a crotch or thick branches for support, she spends a few days building an open cup-shaped nest using weeds, twigs, bark, grasses and deer hair.
The female lays three to four eggs, which are generally bluish-white in color, rarely with light brown or purple spots. The eggs are roughly three quarters of an inch long and one half inch wide. The female incubates the eggs for 11 to 14 days and provides almost all the insects needed to feed her young. Within twelve days the young birds are able to leave the nest. The male sometimes takes over feeding the brood, especially if his mate is preparing a new nest for a second brood. Depending on the location of the breeding territory, the birds begin their migration flights from September through November. They generally fly at night for safety, using the stars for celestial navigation.
The indigo bunting is a small bird roughly five inches long with a wingspan of eight inches. They weigh barely one half ounce. Yet this bird makes two annual migration flights that can exceed 1,200 miles. Many birds winter in Mexico, the Caribbean islands or South America. Wandering vagrants have been documented in far-flung locations like Denmark, Iceland and even Serbia. Life is full of risk for these intrepid travelers so the average life span is three to four years but one banded male was recaptured at more than 13 years old.
Along with other shrub land species, indigo buntings are falling in numbers as urban areas expand and marginal farmland reverts to mature forest. The North American Breeding Bird Survey showed their population declined 31 percent between 1966 and 2014. Fortunately, their numbers are well above the level of threatened status with the international Union for Conservation of Nature estimating a population exceeding 28 million. Maine is near the northern limit of their breeding range but coastal areas like Harpswell are attractive to indigo buntings. Preserves like Curtis Farm are popular spots to see these lovely birds.
If you want to attract indigo buntings to your yard it is recommended that you use small seeds like thistle or niger. Live mealworms should prove attractive especially if birds are feeding nearby chicks. If their beauty and lilting song is not enough for you to favor the indigo bunting, consider that this is one of the few birds happy to eat the noxious browntail moth caterpillar!