By Courtney Brockman, UM News Service

MISSOULA — Every social network has its fake news. And in animal communication networks, even birds discern the trustworthiness of their neighbors, a study from the University of Montana suggests.

The study, recently published in the top science journal Nature, is the culmination of decades’ worth of research from UM alumni Nora Carlson and Chris Templeton and UM Professor Erick Greene in the College of Humanities and Sciences. It sheds a new light on bird social networks.

“This is the first time people have shown that nuthatches are paying attention to the source of information, and that influences the signal they produce and send along,” Greene said.

Carlson, Templeton and Greene shared an interest in trying to crack the Rosetta Stone of how birds communicate and collected bird calls over the years.

Each bird species has a song, usually sung by the males, for “letting the babes know ‘here I am,’” Greene said, as well as staking out real estate. Their loud and complex calls usually ring out during breeding season.

But for warning calls, each sound stands for a specific threat, such as “snake on the ground,” “flying hawk” and “perched hawk.” The calls convey the present danger level and specific information. They also are heard by all species in the woods in a vast communication network that sets them on high alert.

“Everybody is listening to everybody else in the woods,” Greene said.

In the study, Greene and his researchers wanted to determine how black-capped chickadees and red-breasted nuthatches encode information in their calls.

In bird communication, a high-pitched “seet” from a chickadee indicates a flying hawk and causes a strong reaction — other birds go silent, look up and then dive in the bushes. Alarm calls can travel quickly through the woods. Greene said in previous experiments they clocked the speed of the calls at 100 miles per hour, which he likens to the bow wave on a ship.

“Sometimes birds in the woods know five minutes before a hawk gets there,” Greene said.

A harsh, intensified “mobbing call” drives birds from all species to flock together to harass the predator. When the predator hears the mobbing call, it usually has to fly a lot farther to hunt, so the call is very effective.

“The owl is sitting in the tree, going, ‘Oh crap!” Greene said.