The Purpose for This Research 

Over the quarantine, due to Covid-19, I picked up interest in evolution, specifically on the topic of Carcinisation, which is a term introduced by L.A. Borradaile (1) that describes an example of convergent evolution in which crustaceans begin to evolve into a crab-like form (McLaughlin, Patsy A., and Rafael Lemaitre). I realized, however, that I was not well informed on the subject of evolution, and I began to learn the foundation of evolution. While doing some background research, I stumbled across an article describing how urbanization has led populations to populations of birds that have to evolve at an incredible speed to thrive and survive in the city, as the urban landscape has taken over their habitat. I wanted to explore further the factors of the city that push a population to evolve. I did not want to research rats or roaches, so I turned to birds, which have shown many genetic changes and morphological changes.

The Stressful Effect of Human Presence

How does living in a city full of humans affect these territorial bird? In the simulation below, click Start Game. Drag the slider labeled human to increase the number of humans in the area. 

As the number of humans increases, the number of birds decreases, as shown in the graph in the simulation (bottom right). There is a statistically significant correlation between the amount of human influence and the birds' diversity and abundance in an area (Figure 2). There is a negative correlation between the abundance of birds and the increase in human influence, as birds that are affected by human impact fledge (leave the nest) half the time than an unaffected bird, as well as having smaller body mass and only weighing 7.2% of the average body weight (Lepczyk, Christopher A., et al).

Humans affect bird populations in many different ways, not just by stressing out these territorial birds into reproducing less. Let's explore these factors and see how they cause an evolutionary change in the population of birds that choose to stay in the urban environment.

The Effect of Skyscrapers

A defining characteristic of an urban environment is the towering skyscrapers that line every sidewalk. You can begin to see the effect the buildings have on these birds by dragging the building sliders. What happens to the bird population as you increase the number of buildings?

As the number of skyscrapers increase, the number of birds decreases again! But why?

These buildings are hazardous for birds while flying, and the reflective glass on these buildings causes millions of collisions per year. Building collisions are the number two cause of death of birds living in urban environments. In a 2014 study, it was found that "265 million to 988 million birds die yearly due to collisions into buildings" (Loss et al.). Additionally, 56% of collisions happen between 4-11 stories buildings, 44% of collisions are with facilities with 1-3 stories, and only less than 1% happen at taller buildings than twelve stories (Loss et al.).

Due to reflecting the sunlight and sky, windows are deemed invisible to birds. However, there is a way to reduce bird-building collisions. A straightforward solution is to turn off the light inside buildings at night to not attract the birds during the night to the facilities. Another way to reduce birds colliding into windows is to provide a way for the birds to recognize that there is glass covering the area, such as an object that could be placed on the window every 5 to 10 cm to allow the birds to realize that there is an object that they need to avoid. Another way is to begin using non-reflective tinted windows since if the windows are no longer reflecting the sky, the windows would be more visible to the birds (Ogden, Evans, and Lesley J). Another solution that focuses on reflection is angling the windows downward to reflect the ground rather than the sky (Klem Jr., Daniel, et al.). 

The Effect of Heavy Metal Pollution Plumage

In urban environments, heavy metal pollutions have been on the rise for decades. Soil in Chinese urban areas have shown "approximately 65% of all the cities have high or extremely high contamination levels of heavy metals in urban soils and urban road dust" (Wei, Binggan, and Linsheng Yang). The pollution comes from traffic emissions, sewage, and industrial emission.

What effect does heavy metal pollution have on the birds? Adjust the slider labeled pollution to find out.

However, the pollution in the urban air actually can cause damage to proteins, lipids, and DNA. A unique way for these birds to detoxify the air pollutant is to incorporate toxic heavy metals like lead, zinc, and copper into their plumage. These feathers are possibly helping to detoxify the bird's bloodstream from heavy metals and reduce the harmful effects by binding to the bloodstream chemicals and removing them by growing the metals into the feathers (Chatelain, M., et al). In a study on Parisian pigeons, scientists found that "when fed the same diet and housed under the same conditions, darker birds remove more zinc—and possibly other noxious heavy metals—from their bloodstream than light-colored birds do" (Chatelain, M., et al).  Removing the oxidative stress will allow the birds to survive longer as studies have shown that the stress has shortened the birds' telomeres without the ability to remove the heavy metals and, therefore, in urban environments, did not survive past the winter.

In the next section, we will explore the availability of food in the urban environment, which introduces the heavy metal into these birds' bloodstreams.   

The Effect of Food in the City on Avians

The availability of food in urban spaces is no surprise   The availability of food has attracted a variety of roaches, mice, and even birds (remember Pizza Rat?). For birds; however, the available food in the urban environment is especially harmful to the birds and the available nutrients affect their birth and fledging rate.

What effect does food availability have on birds? Drag the slider labeled food to see what happens. 

a cornerstone in birds' vitality" (Arizona State University).  Carotenoid is present everywhere in the bird's reproduction process. From being in the Yolk aiding in growth, health, and coloration, to being in the testes of males to prevent sperm damage and increase fertilization chances. 

However, due to the urban environment, this type of caterpillar is not as widely available. When this vital nutrient is reduced there is a decrease in the effectiveness of the sperm leading to less breeding success, and even the chicks that are born are less likely to leave the nest  (Isaksson, Caroline).

The next factor of food in the urban environment that affects birds' vitality is the amount of sugar and cholesterol in the food. Research has found that birds will react to those unhealthy ingredients the same way that a human's body will respond to those ingredients. Birds will also begin to get higher sugars, form diabetes, have higher cholesterol levels, and be more susceptible to heart attacks.

Conclusion

As you have learned from these simulations, many factors contribute to the evolution of birds in the city. They are subjected to selection pressures, or factors that make it difficult survive. You should be able to answer these questions:

• how do territorial birds respond to the presence of humans?

• how do skyscrapers affect birds?

• how does heavy metal pollution change plumage color?

• how does excess food availability actually hinder reproductive success?

The simulation was built on existing, published data. Although it can teach valuable lessons of how humans can affect other organisms and their evolution, there are plenty of intricacies and multivariable dependencies that have not been explored. 

Reflection on The Research

1. Text Editors: there is a lot of text editor software to hold your code, but some are more beginner user-friendly! The two text editors that I have found to have the most user friendly are:

   1.  Visual Studio Code: This is the most user beginner friendly text editor as it will suggest code that you want to write and have a lot of useful extensions such as the live website, which will show you what you are trying to code on a website. This Editor is also the most popular text editor, so many people who will do coding tutorials will use this Editor.

   2. Atom: This is another great text editor, it is a bit less user-friendly, but in return, it contains all of the best open-source websites and forums that you will need GitHub. The Editor is also completely customizable, so you can make it super unique to how you code.

   3. You can also customize the theme for both of these text editors, which will change the color of the code and make it look a lot more aesthetically pleasing.

2. Opensource websites: Opensource websites are what their names state. They are websites where other coders will share their code completely free to download other's code and change their variable To fit your own needs! 

   1. Github: Github is the overlord of coders. The most comprehensive website contains any code that you would need and any coding language that you would like to have it in. When you're beginning code, use Github to find fun projects and look for examples, you can upload your code as well! 

      1. This link is of my code if you would like to look at my code or modify it for your use: https://github.com/quanha22/quanha22.github.io. 

   2. StackOverflow: Stacksoverflow is like a yahoo answer but specifically just for coding. Whenever you want your code to be examined or are having a problem with how your code is running, someone on open stacks has had the same issues, and if not, others are super willing to help you solve your code!

3. The Coding Train: This is a fantastic resource for beginner coders, this is a youtube channel with tutorials in coding simulations and games, but he also has a whole playlist teaching the foundations fundamental in giving me my basic understanding of coding. 

4. Always leave comments: I said this earlier in my reflection video, but it is essential to leave comments while you code. My biggest mistake was not leaving comments, and therefore I spent a significant amount of time trying to figure out what I had coded the night before. However, if I left comments while I was coding, I would have saved so much time.

5. Coding at times can be challenging: Coding is a tedious task, and there are moments where you feel as if you have to give up, but remember that nothing is impossible if you keep working on it, you will improve, and by the end, you will create a fantastic product that you will be super proud of!

References

1. McLaughlin, Patsy A., and Rafael Lemaitre. " Carcinization in the Anomura - fact or fiction? I. Evidence from adult morphology". Contributions to Zoology 67.2 (1997): 79-123. https://doi.org/10.1163/18759866-06702001 Web. 

2. Loss, Scott R., et al. “Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability.” The Condor, vol. 116, no. 1, 2014, pp. 8-23. https://doi.org/10.1650/CONDOR-13-090.1. 

3. Digitalcommons.Unl.Edu, 2021, https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1002&context=flap.

4. Igsnrr.Cas.Cn, 2021, http://www.igsnrr.cas.cn/news/kyjz/202011/P020201102585628472049.pdf.

5. "Carotenoids Are Cornerstone Of Bird's Vitality". Sciencedaily, 2021, https://www.sciencedaily.com/releases/2009/02/090213114154.htm.

6. "Why Dark Pigeons Rule The Streets". Science | AAAS, 2021, https://www.sciencemag.org/news/2014/03/why-dark-pigeons-rule-streets.

7. Tsang, Ling Ming, et al. “Hermit to King, or Hermit to All: Multiple Transitions to Crab-like Forms from Hermit Crab Ancestors.” 2011. https://www.researchgate.net/publication/51565889_Hermit_to_King_or_Hermit_to_All_Multiple_Transitions_to_Crab-like_Forms_from_Hermit_Crab_Ancestors .

8. Chatelain, M., et al. “The adaptive function of melanin-based plumage coloration to trace metals.” https://royalsocietypublishing.org/doi/10.1098/rsbl.2014.0164. 

9. Ogden, Evans, and Lesley J. “Collision Course: The Hazards of Lighted Structures and Windows to Migrating Birds.” 1996. https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1002&context=flap .

10. Wei, Binggan, and Linsheng Yang. A review of heavy metal contaminations in urban soils, urban road dusts and agricultural soils from China. 2009, http://www.igsnrr.cas.cn/news/kyjz/202011/P020201102585628472049.pdf .

11. Hardman, S.I, and S. Dalesman. “Repeatability and degree of territorial aggression differs among urban and rural great tits.” 2018. https://doi.org/10.1038/s41598-018-23463-7 .

12. Good Living. “Everything you need to know about magpie swooping season.” 17 August 2017, https://www.environment.sa.gov.au/goodliving/posts/2017/08/magpie-swooping-season.

13.  Klem Jr., Daniel, et al. “Effects of window angling, feeder placement, and scavengers on avian mortality at plate glass.” 2009. https://www.researchgate.net/publication/232673878_Effects_of_window_angling_feeder_placement_and_scavengers_on_avian_mortality_at_plate_glass.

14. Lepczyk, Christopher A., et al. “Human Impacts on Regional Avian Diversity and Abundance.” 2008. https://www.researchgate.net/publication/5558557_Human_Impacts_on_Regional_Avian_Diversity_and_Abundance.

15. Isaksson, Caroline. Impact of Urbanization on Birds. open access, 2018, https://library.oapen.org/bitstream/handle/20.500.12657/22941/1007220.pdf?sequence=1#page=240 .