For the Birds Radio Program: Indigo Buntings
By mid-July, many birds are no longer singing, but one wonderful exception is the Indigo Bunting. And Indigo Buntings break another rule as well, singing throughout the day, even in the heat of the afternoon. Indigo Buntings generally sing from a very exposed perch—often in a high, dead branch or in a tree snag, and they’re pretty common in brushy habitat, so one would think they’d be easy to find. But they’re usually backlit from atop their high perches, and the weird optical properties of blue feathers make them inconspicuous and even dull unless you happen to catch them at exactly the right angle. If you’re lucky enough to accomplish this, you’re in for a treat. No other eastern bird has blue of this shade and intensity, and something about this bird’s tiny but plump body and tiny stub of a bill makes it especially endearing. Females are a dull brown, with soft, subtle bluish overtones, but are tricky, most easily recognized by size and shape.
Baby birds require lots of protein and calcium to build bone, muscle, organs, skin and feathers, so even though much of the year Indigo Buntings feed primarily on seeds and berries, many parent birds spend the summer searching out animal food for their young—usually insects, spiders, and other small invertebrates. Indigo Buntings turn up at bird feeders most often in during spring migration, especially after the weather has been bad. By the time they start nesting, they usually lose interest in seeds and feeders, focusing more on insects and other natural food. That’s when I get lots of calls from people worried that something happened to them, but it’s virtually always just a matter of their change in diet. About 10% of father buntings help feed their nestlings and fledglings. In cases where they do, the young fledge sooner and there’s a higher likelihood that there will be enough time for a second brood to be successful as well, so paternal care may help ensure that helpful fathers pass their genes to the next generation. But those males that don’t help may have more time to sing, attracting more mates, and in that way improve their own chances of passing their genes to the next generation.
Either way, fathers always pass their genes on to their own young but they don’t pass their songs on to their sons. Some birds learn nuances of their song in the nest, from listening to their father, and some birds know their songs innately. But male Indigo Buntings don’t learn their song until their own first breeding season when they’re almost a year old, when they pick up the song patterns of the buntings in their new area. The nuances in individual bunting songs are rather subtle, so it takes a lot of practice to distinguish buntings in one place from those in another by voice. But no matter where they hail from, Indigo Buntings all sound rather like goldfinches, only with paired notes, so the rhythm is pretty easy to recognize with practice. Listen and look for them—you won’t be sorry!