Making new friends has its challenges, even for birds.
Researchers at the University of Cincinnati found that monk parakeets introduced to new birds will "test the waters" with potential friends to avoid increasingly dangerous close encounters that could lead to injury. They gradually approach a stranger, taking time to get familiar before ramping up increasingly risky interactions.
The study was published in the journal Biology Letters .
"There can be a lot of benefits to being social, but these friendships have to start somewhere," said Claire O'Connell, the study's lead author and a doctoral student in UC's College of Arts and Sciences.
O'Connell collaborated on the study with UC Associate Professor Elizabeth Hobson, former UC postdoctoral researcher Annemarie van der Marel, and Princeton University Associate Professor Gerald Carter.
"Many parrots, for example, form strong bonds with one or two other birds. Partners often spend most of their time together, preen each other or sometimes form reproductive relationships," O'Connell said. "Generally, maintaining these strong social bonds is associated with decreased stress and higher reproductive success."
But making that first contact carries risk, especially when animals are unfamiliar to one another.
O'Connell said birds that don't welcome a newcomer's attention can react aggressively, which can lead to injuries.
Researchers combined groups of wild-caught parakeets in a large flight pen. Some parakeets were strangers to each other. They collected data on when and how new relationships formed by studying how close the birds approached over time and which birds groomed each other or engaged in other friendly behaviors.
Then they analyzed more than 179 relationships using computational methods and statistical models to determine whether relationship formation followed the pattern predicted by previous studies exploring the theory of testing the waters.
"Capturing the first moments between strangers can be challenging, so we were really excited that our experiments gave us the chance to observe that process up close," O'Connell said.
They found that strangers were more likely to approach each other with caution compared to birds they knew. Stranger birds took time to share space before eventually perching shoulder to shoulder, touching beaks or preening others. Some strangers escalated further to sharing food or mating.
The UC study had results comparable to a 2020 study of vampire bats that found that newcomers likewise test the waters, gradually escalating from social grooming relationships to food-sharing relationships with trustworthy partners.
"What's really fascinating about testing the waters is how intuitive it feels," O'Connell said.
"I can definitely relate! I started observing the parakeets shortly before I moved to Cincinnati to start graduate school," she said. "I was excited but also a little nervous about making new friends. At the same time, I was literally watching the parakeets make new friends themselves, although some did better than others. I started realizing there may be something I could learn from the parakeets."
