It’s happening. Warm days have triggered a spectacular natural phenomenon unique to the hardwood forests of the eastern United States: the emergence of “Brood X” cicadas after 17 years developing as nymphs underground.
Once soil temperatures reach 64 degrees F, nymphs crawl into tree canopies, complete their molt into adults, feed, mate, lay eggs, and die — all within a few short, noisy weeks. Brood X (aka Brood 10) cicadas are part of a remarkable group called “periodical cicadas.” Of the 15 species of periodical cicadas found worldwide, none comes close to matching the life cycle length of the three Magicicada species that comprise Brood X. This BBC Earth video is a fabulous primer on their life cycle and shows how important they are for a variety of critters up the food chain.
This video features the “song” of the male cicada. Quite honestly, I find the sound both creepy and irritating, like the cheesy soundtrack of a 1950s sci-fi movie!
Cicada experts predict Brood X will be among the largest and densest swarm in recent history, appearing in three distinct hot spots across portions of Pennsylvania, Delaware, Washington DC, Illinois, Ohio, Indiana, Georgia, and Tennessee. Cicada chasers are reporting emerged adults in TN, northern GA, and central NC via the Cicada Safari mapping app.
Imagine being a bird steeped in all that insect biomass; to have more easily obtainable, nutritious food than you can stuff down your and your nestlings’ gullets. Just how does this periodical super-abundance of food influence breeding bird populations?
Not surprisingly (given logistical scope and scale) only a handful of studies have delved into this question. One study by Koenig and Liebhold looked into the population effects of periodical cicadas on avian predators. Their working hypothesis was that periodic cicadas were an important “pulse” resource that likely had strong “bottom-up” effects on avian communities.
Using 37 years of North American Breeding Bird Survey data, they analyzed 24 bird species found in eastern U.S. hardwood forests known or likely to eat Magicicada spp. They found that cicada eruptions significantly influenced 15 of 24 (63%) species.
Eight species, including Red‐bellied Woodpecker, Blue Jay, Common Grackle, and Brown‐headed Cowbird, saw a population bump of 10% following cicada emergences — ”presumably attributable to high survivorship or reproductive success.”
Red-headed Woodpecker, American Crow, Tufted Titmouse, Gray Catbird, and Brown Thrasher had low populations in cicada years compared to years without cicadas, with numbers spiking the following year and then stabilizing. The authors speculated this may be an indirect effect of the prior emergence event 13 or 17 years earlier. In other words, cicadas’ cycles may be timed to manipulate populations of predatory birds — an adaptive benefit to reduce predation pressure on cicadas.
Low bird populations found in cicada years may also be attributed to the loudness of cicada calls. The sheer volume of cicada buzzing may interfere with surveyors’ ability to hear singing birds, thereby underestimating a local population. Loud cicada song may also drive birds into quieter areas with less acoustic competition.
In my research for this DC, I came across a delightful website, Cicada Mania, testifying to the fact that cicada nerds out-nerd bird nerds by a factor of a few billion.
"There's an awesomeness to it because you're surrounded by thousands, maybe millions of these creatures that weren't there the day before. It’s like an alien invasion, like being in a movie." ~Dan Mozgai, Cicada Safari citizen scientist
There is much to see and learn on Cicada Mania about Brood X and all things cicada — even a Cicada Wedding Planner to make sure your nuptials don’t include winged wedding crashers (“Do Consider renting a hall. Sure, grandma’s yard is pretty, but nothing beats peace of mind”).
I hope you Easterners get to soak up the magic of this year’s big cicada emergence, one of the true insect wonders of our world!
Happy May Everyone!
~The floor is yours to share your birdy thoughts, photos, and stories~