Each time Todd Hochberg passed the Regenstein Hall of Music this spring, he searched the clusters of mud nests tucked under the overhang for signs of life and was disappointed each time. They remained empty.
However, when June rolled around, the nests began to bustle once again as hundreds of cliff swallows returned to their nests to breed. Hochberg was relieved.
“I look forward to them every year,” said Hochberg, a photographer. “They’re a positive part of my Northwestern experience.”
Though they are a recent addition to Evanston’s bird community, the swallow population has been expanding every year. They have also proven to be more than just a joy for onlookers.
Like all predators, the swallows in Evanston reduce the population of their prey. In this case, their prey includes mosquitoes.
According to Judy Pollock, director of bird conservation at the Chicago Region Audubon Society, this is the fourth species of swallow to inhabit the Northwestern campus. These birds are native to the canyons of the West, where their russet-colored throats and pointed wings make them an easily recognizable feature in the landscape.
However, they have become more abundant in the Midwest during the last 20 years thanks to the increase in buildings and bridges under which they can nest.
“There were no cliffs here before,” said Libby Hill, program chair for the Evanston North Shore Bird Club. “Now we’re building them, and now they’re here.”
They’re here and, according to David Willard, recently retired collection manager of birds at the Field Museum in Chicago, they’re helpful.
“I can’t say with certainty how many mosquitoes would be bothering us without them,” Willard said, “but they do exert control over mosquito populations.”
Peter Capainolo, an ornithologist at the American Museum of Natural History, agrees.
“Swallows certainly play a role in population control,” Capainolo said, “though many people won’t necessarily notice if they’re being bitten by less mosquitoes.”
Though Capainolo conceded that swallows cannot eat every mosquito, the numbers are impressive. Statistics released by the Audubon Society show a single swallow can consume 60 insects per hour. Given the hundreds of swallows living on campus – nearly a thousand, according to Pollock – the implications are staggering.
The swallows will need to be particularly active this year, as the mosquito season is predicted to be another bad one. According to the North Shore Mosquito Abatement District, which monitors and attempts to control mosquito population within its area, the 2010 population increase was the largest in 10 years.
“We’ve already had a couple of weeks this year where populations were pretty excessive,” said David Zazra, North Shore Mosquito Abatement communications manager. “Right now we’re in a small reprieve, but we can’t tell right now how bad it will be.”
