As Newsies and Pizza Rat can tell you: you’ve got to be clever and tough if you want to make it in the city. Sure, it’s common knowledge, but it’s also scientifically true, at least for birds. Ornithologists say that urban finches are both smarter and more disease-resistant than their country cousins. The researchers recently published their report on the subject in the journal Behavioral Ecology.
Jean-Nicolas Audet and his colleagues wanted to compare the birds' problem-solving skills and their immunities. To do so, they needed to find members of the same species living in two different environments. With populations of bullfinches present in both developed and open areas, as well as an ornithological research station, Barbados made a perfect test site for them.
The researchers used gentle-capture nets called mist nets to capture 53 Barbados bullfinches (Loxigilla barbadensis) from eight areas on the island—four rural and four urban. They brought the birds back to the lab and gave them a few days to settle in. Once the birds were acclimated, the tests commenced.
Audet and his colleagues rigged up a number of bird problems, each with a seed goal. In one puzzle, a bird could only reach a cup of seeds by using a stick to pull the cup closer. In another, the bird had to remove a lid or pull a hook to open a little drawer full of seeds. Each bird went up to 15 rounds with each test, with a researcher recording their successes and failures.
To test the finches’ disease resistance, the researchers injected each bird with a tiny dose of an immune-activating protein called phytohemagglutinin (PHA). Animals with strong immune systems who are given PHA will have a little inflammation at the injection site, so the ornithologists measured each bird’s wing to check for swelling.
When all the tests had been scored and the results analyzed, the city birds emerged as clear winners in both cleverness and immunity—a fact that surprised the researchers.
"Since urban birds were better at problem-solving,” Audet said in a press statement, “we expected that there would be a trade-off and that the immunity would be lower, just because we assumed that you can't be good at everything. It seems that in this case, the urban birds have it all."