Sentinel warning calls seem to be universally understood by birds • Earth.com

Sentinel warning calls in birds can be understood globally, transcending continental boundaries, according to a new study.

This discovery not only expands our understanding of animal communication, but also suggests an evolutionary convergence in vocal signals related to danger.

Danger signs

Henry Pollock, executive director of the Southern Plains Land Trust, and graduate student Joanna Dominguez led the research. University of Illinois Urbana-Champaign.

Sentinel species, such as the Paridae family, are important for their distinctive alarm calls in mixed species groups. These calls, like the chick’s „chick-a-dee-dee-dee,” are recognized by many different bird species, emphasizing their role as universal signals of danger.

Anti-predator behavior

„Many animals form mixed-species groups, and this is thought to be an anti-predator behavior,” Pollock said. „There’s safety in numbers, and there’s an advantage to surrounding yourself with a variety of eyes and ears.”

„However, you need to understand the information others around you are giving you to use it.”

Study focus

The research team set out to investigate whether bird communities on three continents—North America, Europe, and Asia—could explain the alarm calls of a previously unknown sentinel, the dusky-throated antshrike, a Central and South American bird known for its sentinel role. .

This study includes contributions from Mark Hauber (GNDP) and international collaborators from Serbia and China.

Amazing results

The experts played the warning calls of dusky-throated ants to different bird flocks. They hypothesized that birds would respond more strongly to familiar local sentinel calls. But the results were surprising.

„We expected to see some kind of response to the calls of the novel antshrike, but predicted that the birds would not respond as strongly to the calls of their own local sentinels,” Dominguez said.

„However, we were surprised to find that there was no statistical difference in how the birds responded to the warning call of local and foreign warblers. Birds responded to the call of an unfamiliar antshrike as if it were a bird they had known all their lives.”

Global recognition

According to the researchers, flocks of birds on all three continents responded equally strongly to the warning calls of an unfamiliar antshrike as they did to the warning calls of a familiar, local sentinel.

Experts say the discovery is universally recognizable for sentinel calls.

For messages that contain important information, such as a warning call for danger, the researchers suggest that evolution can combine similar sound calls to help get the message across faster.

central theme

„These calls are more easily recognized across species because they have a central theme—basically something unique and conserved about them despite millions of years of evolutionary history,” Dominguez explained.

„In other animals there is research on specific amplitudes and frequencies of sound that can cause innate responses, even in animals that are unfamiliar with those sounds. Our study will help researchers identify what those acoustic components might be for birds.”

Signal recognition

„What’s surprising is that our findings are consistent with completely different bird communities on three different continents, suggesting that there are some signals encoded within these sentinel alarm calls that the birds respond to, independent of previous experience with that signal,” Pollock explained. .

„This really highlights that signal recognition is not always something that needs to be learned through environmental experience.”

Future research opportunities

The study opens the door to many future research directions, the researchers said. They noted that possible next steps are to test the birds through the calls of other sentinels and gain greater granularity in terms of behavioral responses.

Defining sentinel species

Dominguez wants to find a common thread among sentinel birds in an attempt to standardize what is classified as a sentinel species across the literature.

„Sentinel species are not very well defined because the term is used nebulously for any animals that are involved in mixed-species foraging and signaling,” Dominguez said.

„There are many birds in the literature that we don’t normally think of as sentinels, and others that may be sentinels that are overlooked. I want to find out if there is a common thread between them and whether the term should be used at the species level or at the flock level.

The study is published in the journal Biology Letters.

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