The fire ant is an introduced, exotic pest species in the U.S. Colonies in the southern states which are responsible for inflicting painful bites on humans and fatal attacks on native wildlife, including cavity-nesting birds. But Purple Martins have turned the tables on fire ants by targeting the flying queens. Turns out they are an abundant, nutrient-dense food source that might just be keeping Purple Martin populations going in the south.
Fire ants form large colonies, and lots of them. One of the keys to their growing population is an extended breeding season - basically throughout the spring and summer, and year-round in warm climates. Breeding activity involves large swarms of flying queens - a single hectare of land might produce 40,000 queens at a time.
Purple Martins take advantage of these swarming flights and capture many of the queens. Each queen is a juicy bundle of fat and protein, just the thing to feed growing young martins. A recent study of martins nesting in Oklahoma found that about a third of the food items fed to the young were fire ant queens. With an estimated one million nesting pairs of martins within the U.S. range of fire ants, the nestlings consume an estimated 1.7 billion fire ant queens each nesting season. Add in consumption by adult martins and we're talking about tens of billions of fire ant queens eaten per year. It's possible that Purple Martins (and Chimney Swifts, Tree Swallows, Red-headed Woodpeckers, and other known predators on fire ants) are keeping the ant populations in check.
And perhaps it's a coincidence, but the southern U.S. is the only area where Purple Martin populations are stable or increasing. Could it be that the pesky fire ant, a super-abundant food source, is propping up those populations?