Trying to live in an urban environment is incredibly challenging. The human population is steadily increasing, and animals are losing their homes. For birds, it can be challenging to communicate with one another due to the different noise levels humans produce daily. For example, on a Monday morning during rush hour, you will see people leaving their homes and taking a car, train, or bus to get to their work destination. Hearing people talking, public transportation, cars honking in traffic, and planes in their flight path all combine to make a discordant mixture of sounds. On the other hand, living in a suburban environment is a different experience. On a Sunday morning, fewer cars will be on the road, and people will be sleeping in and enjoying their free time with family and friends. In this case, there is a little sound created.
Birds living in urban environments must adjust their vocal communication based on the human production of noise levels. This is because birds depend on different communication signals, whether there’s a predator around, food nearby, or trying to mate. The way birds make this work is by modifying the communication of their signals to the transmission of human noise so that it is effective. In addition, birds can reduce signaling by changing the elements of the songs they produce. This is referred to as the “Lombard Effect,” when animals increase the size of their vocals in scenarios when background noise is much louder.
A study was conducted in Hong Kong, and bird songs and noise measurement data were recorded in 22 sites across the city between the 17th of June and the 8th of September. Researchers recorded birds that sang within the sampling period. The recording began as the birds started to sing, and the recording concluded when the singing stopped. In this study, four different bird species were included: The Common Tailorbird (Orthotomus sutorius), Eurasian Tree Sparrow (Passer montanus), Swinhoe’s White-eye (Zosterops simplex), The Red-whiskered Bulbul (Pycnonotus jocosus). From the four total bird species, 272 individuals were studied and recorded during the sampling period.
In this conducted study, the completed results were found to be super astonishing. Since there were four different bird species studied and recorded, they were all individually recorded. The Swinhoe’s White-eye (Zosterops simplex) had a negative relationship between vocalizations and noise level within the urban areas, even though no cicadas were present. Moving on, the Eurasian Tree Sparrow (Passer montanus) had a higher frequency since there were no cicadas. Therefore, they were able to raise their frequency. In the Common Tailorbird (Orthotomus sutorius), there was a significant relationship between location and cicada presence. There was increased noise level and frequency in the urban landscape when cicadas were present. Lastly, Red-whiskered Bulbul (Pycnonotus jocosus) showed that the maximum frequency was shallow across all locations when cicadas were present. Frequency and noise levels were not affected.
Work Cited: https://doi.org/10.1093/beheco/arab058
