How Do Birds Sing Over City Noise?

Have you ever raised your voice because someone could not hear you? Imagine talking to a friend in a peaceful park. Now imagine trying to talk on a busy street or near a highway. The traffic noise makes it difficult to communicate, and you may speak up so your friend can hear you. Other animals have this issue, too. Songbirds can live in various environments, such as forests and grasslands, and they use their songs to communicate with each other. As cities grow and invade their habitats, birds may find it harder to hear one another. To be heard, some birds might change their songs. For example, some birds in cities sing louder, longer, or at a higher pitch than rural birds. Researchers are studying this problem: how does human-made noise affect birdsong? Answering this question is important so we can protect the birds around us and their habitats.


Figure Figure
A male American robin. Robins' songs can sound like "cheerily, cheer up, cheerily, cheer up" . American Here is an American robin recording contributed by Eric Zawatski, audible at the second mark: https://www.xenocanto.org/ .
robins live in many parts of the United States, so many people living there may see and hear them in their backyard every day. The graph shows the robin's song and can be read kind of like reading sheet music. The x-axis shows time, so the graph is read from left to right. The y-axis shows the pitch, similar to the way musical notes are written on a sta at di erent heights.
moving air through an organ called the syrinx. While you may have SYRINX "Voice box" organ found in birds that produces sound with vibrations caused by air flow.
heard birds singing, not all birds are songbirds. Chickens and pigeons,

SONGBIRDS
Birds that have the anatomy to support (usually melodic) song.
for example, are not songbirds, and they only use short, simple "calls" to communicate. In contrast, songbirds, such as sparrows and robins, sing pretty melodies that you may hear around your neighborhood ( Figure ). Generally, male songbirds sing to attract mates and to communicate with other members of their species. Males even use songs to defend their territories from other males. Songs are an important social tool used by birds, and the ability to produce a song that can be heard easily can a ect whether a bird will successfully find a partner and raise chicks.

HOW DO BIRDS LEARN TO COMMUNICATE?
Songbirds are grouped into two categories based on how their songs develop when they are young. Some species learn their songs-not in the classroom, but by listening to the adults in their population. These  learn their songs. They can sing without help from adults, which is a lot like other animals ( Figure ). Dogs do not have to learn to bark, cats do not have to learn to meow, and chickens do not have to learn to cluck! Oscines could have an advantage over suboscines when they need to modify their songs due to environmental pressures. For example, some oscines have been shown to sing louder when researchers played loud background noise nearby [ , ]. In urban environments, singing URBAN Related to a city or densely populated area.
louder in response to noise might help a bird be heard by others, and the ability of oscines to learn their songs might help them to change their songs more easily [ ], but scientists are still trying to figure this out.  Multiple studies have been done to test how birds change their songs in noisy places. One notable study recorded common blackbird songs in the inner city of Vienna, Austria and in the woods outside of the city [ ]. The two blackbird populations were about miles apart. The songs were measured early in the morning when songbirds most commonly sing. In the city, the pitch of the loudest part of the song was much higher than that of the rural birds in the woods (Figure ). Singing in a higher pitch would be like making the sound of a flute instead of a tuba! The city birds sang fewer notes than the rural birds and sang much earlier in the morning, possibly to beat the loud car tra c. In the city, birds also sang faster-instead of pausing for a certain time between their notes, they would shorten these pauses and rush their songs [ ].
This change in songs is also seen with many other bird species around the world! Another study analyzed the songs of bird species kids.frontiersin.org October | Volume | Article |

Figure Figure
A study in Austria supported the hypothesis that urban noise can change birds' songs. Blackbirds in urban environments sang at a higher pitch than the rural blackbirds (top) . The Here are examples of blackbird songs from urban and rural locations in Austria (These recordings are not from the original study but were found on citizen-science databases

WHY DOES THIS MATTER?
People are creating challenges that organisms must face daily. Our cities are invading areas that used to be natural habitats for many species. By building on those lands, we are a ecting the organisms around us. It has been shown that tra c noise alone can scare birds away or influence them to change their songs [ ]. Birds evolved their songs for the environments they live in, and as their habitats get noisier and noisier, they are adjusting many of their behaviors. It may not seem like a big deal that songs are changing in many Maybe some of the bird songs you record will help to make the world a healthier place for both birds and the humans who enjoy their songs!

IMAGE CREDITS
The image of the boy in a suit in Figure   . doi: . /frym. .

CONFLICT OF INTEREST:
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
COPYRIGHT © Kantorek, Searfoss and Creanza. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

DOROTHY, AGE:
I love all kinds of science, but especially space sciences. I love reading fantasy and science fiction especially about space travel. I want to go Mars someday or at least contribute to the mission to Mars. I like playing Minecraft and Roblox with my little brother. I also love soccer, mountain biking, and taekwondo. I currently live in Germany but I am from Temple Terrace, Florida, and look forward to returning to Florida in a few years.

NYSSA KANTOREK
Nyssa graduated from Vanderbilt University with her bachelor's in Neuroscience with a minor in Psychology. While at Vanderbilt, she conducted research with the Creanza Lab specifically in urbanization and city noise and how that a ects birdsong in species such as the northern cardinal. Currently, her project focuses on how northern cardinals in Nashville respond to sources of noise such as buildings and roads. Moving forward, she will be attending UT Southwestern Medical School to continue to pursue her interests in biology and spatial analyses as a physician.

ABIGAIL SEARFOSS
Dr. Searfoss received her PhD from Vanderbilt University in . Her doctoral research focused on developing new computer-based tools to break down complex bird songs into smaller pieces that can be measured and compared. She then used this computer program to study the songs of a small bird called the Chipping Sparrow. She asked questions like: Does the Chipping Sparrow's song sound di erent in the Eastern and Western United States? Do Chipping Sparrows sound di erent kids.frontiersin.org October | Volume | Article | now than they did in the s when people began recording them for the first time? Since graduation, Abigail has been working at an education technology startup in Nashville.

NICOLE CREANZA
Dr. Creanza is an Assistant Professor of Biological Sciences at Vanderbilt University. Her research focuses on behavioral evolution: how behaviors that have to be learned, like bird songs and human languages, change over many generations. In her lab at Vanderbilt, she works with students on to answer two main types of questions about behavioral evolution. First, if we study lots of birdsong recordings, can we find patterns-such as di erences between urban and rural songs-that teach us how birds are using their songs? Second, can we build simulations (like automated video games!) that show us how the rules of the game a ect how behaviors change over time? Even though bird's songs are not exactly like languages, we can ask similar questions about languages and how they have changed throughout human history. *nicole.creanza@vanderbilt.edu