“I Almost Flew Out of My Feathers”: Alarm Calling in Noisy Minors

Have you ever-yelled “heads up” at a baseball game or screamed “Stop” to someone about to walk into a dangerous situation? As humans, we have developed many specific warnings that are easily communicated and used in our everyday life. These warning calls protect us from unseen dangers. Many other animals have a similar way of communicating and many scientists created experiments testing the “ urgency-based” alarm calls of different species.  Four scientists, Lucy Farrow, Samantha Doohan, and Paul McDonald set their sights studying on birds; specifically Manorina melanocephala, otherwise known as noisy miners. The 4 scientists set up a group of experiments to test 1: if there were different types of alarm calls and 2: did a specific alarm call elicit a specific response.

The 4 scientists used vocal recordings and playback experiments on 2 colonies noisy miners, located in the New England region, in order to test the significance of warning calls. The first colony was located within the camping grounds of Dumaresq Dam, where the birds were continuously exposed to human campers. The second colony was not greatly affected by human presence and was located at the University of New England’s Newholme Field Research Station. Both research locations consisted of dry woodland and contained both aerial and terrestrial predators, such as birds of prey, snakes, and other mammals.  A total of two experiments were tested. The first experiment’s purpose was to distinguish if the type of alarm call produced was specific to the stimulus the bird was exposed to.  During the 15th to the 16th of December 2016, an individual observer would approach the noisy miners within 10meters and stay still for 1minute allowing the birds to adjust to their presence.  After approximately 4 seconds a second observer would record the birds’ specific responses, specifically noting its vocalizations and the number of noisy miners present. In order to simulate an aerial predator, the first observer threw a hat high into the air, while the second observer took note of the birds call, specifically the number of syllables and if other noisy miners joined in on the alarm after the first 4 seconds. Once the hat rested on the ground for four seconds observer two took notes of how the alarm calls changed, including syllables, and the number of noisy minors participating. This first experiment, showed evidence supporting that the noisy miners’ alarm calls were different when referencing an air-born predator and a terrestrial predator, therefore scientist moved on to their second experiment. The second experiment tested the flight response of noisy minors exposed to aerial and terrestrial alarm calls. Alarm calls of various types were recorded between February and August 2015 in the Dumaresq Dam colony using portable Professional Solid State Recorders attached to specific birds identified with colored bands. The raw recordings were then organized and analyzed. The alarm calls of the noisy minor consist of single syllables that occur rapidly and repeatedly, organized by irregular pauses called “bouts”. The best samples of both terrestrial and aerial alarm calls from Dumaresq Dam and the Newholme Field Research Station were selected. To create a more reliable presence of birds five artificial feeder locations were placed in both colonies.  Next, recording systems and speakers were set up 20 meters away from the feeders at a 90-degree angle. Then an observer hid in hide 20 meters away from the feeder and controlled the playbacks and recorded the birds’ responses. The responses recorded were peck rate toward food before stimuli and the peck rate towards food 10 seconds post stimuli. The different stimuli played were terrestrial and aerial alarm calls from birds of the same colony and of birds from a foreign colony. The second experiment found that noisy minors fled more readily when exposed to aerial playbacks rather than terrestrial playbacks.  They also discovered that there was a faster response to playbacks of birds from the same colony compared to unfamiliar playbacks.

The study shows that noisy minors are socially complex and do posses the ability to communicate referential signals, cueing each other when and where predators are located.  In conclusion, prey species such as the noisy minors have evolved a wide variety of strategies to avoid predation such as “urgency-based” alarm calls. This opens up a range of questions about the intelligence of noisy minors and other avian species. One might also be interested in discovering the relationship between intelligence and brain size; and how this may affect a species survival. Though we as humans may believe we are far removed from the rest of the animal kingdom it is important to realize to commonality between our communication. The next time you hear a bird screeching, they may be giving the “heads up” about you.

Farrow, F., L., Doohan, J., S., G., P., & McDonald. (2017, March 21). Alarm calls of a cooperative bird are referential and elicit context-specific antipredator behavior. Retrieved from https://academic.oup.com/beheco/article/28/3/724/3076238