No city park or town plaza is complete without the presence of ubiquitous house sparrows — birds so resourceful and adaptable that they can be found even at remote ranches with just a couple of trees. House sparrows are the little brown birds, often with black bibs, that hop around on the ground, cadging bugs, leftover French fries and sandwich crumbs.
Yes, these nonnative sparrows thrive in North America. Also known as English sparrows, a flock of 50 birds were introduced to New York from the Old World in 1853. Within decades their population had mushroomed to more than 150 million birds spread across the entire continent.
One of the reasons for this phenomenal success is that house sparrows love human company, and the places where humans plant trees, grow crops and feed horses and cows. House sparrows are also pugnacious and have been recorded stealing nests from more than 70 species of birds, earning them the wrath of conservationists concerned about native birds.
But, new research pinpoints another surprising reason for the sparrow’s success. Scientists at the University of South Florida have reported that house sparrows entering new areas alert their immune systems to watch for disease-causing microbes they haven’t encountered before.
This might give house sparrows colonizing new sites a higher survival rate than native birds that have been in the area longer. It’s a tendency that might explain why these ubiquitous birds of city parks are so successful—and perhaps even why some other invasive species thrive too.
Earth Notes is produced by KNAU and the Sustainable Communities Program at Northern Arizona University.