User:AloofCanine72/How Human Infrastructure Impacts Birds’ Ecosystem

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Migratory birds shift their geographic distribution each year, moving between northern breeding grounds and southern sites where they overwinter [REF]. The long-distance migration of birds can cover distances of up to XXXXX km, and is the cause of substantial mortality [REF]. Many factors can impact bird mortality including light pollution in urban areas [REF]. In an effort to reduce the impact of human activities on migratory birds, the United States has proposed a number of regulations [REF]. There have been solutions to bird collisions such as reducing light usage, removing reflective glass, and using materials for windows that promotes bird safety during seasonal migration. As a result, statistics has shown that bird demographics has increased its survival rate in an urbanized environment.

Introduction

picture of a study made in 1915 for bird migration patterns

Birds use established migratory routes for migration. One such route is called the Atlantic Flyway which is located along the east coast of North America, between the Appalachian Mountains and the Atlantic Ocean [REF]. Right now, in current times, this flyway is a risk for birds to take. As humans industrialize and expand territories to which trees were cut down and roads are built, the terrain for the birds rapidly changes. Not only that but now skyscrapers were the new innovating building that engineers and builders can start making. Tall window structures that reach the clouds. But how does this affect birds directly? There are only a few research articles that describe the potential impacts on bird populations when it comes to Human infrastructure. From the National Library of Medicine, they put out a number that says, "365-988 million birds killed annually in the United States [due to building collisions]". The range is so large cause of the limitations to be able to find so many birds in a given day. The most notable for birds slamming into clear glass windows in New York is all that these tall buildings are known for. In addition, other research articles show more cities having similar effects such as Minnesota.

Infrastructure

As people start building larger skyscrapers with reflective material, a problem can occur when birds start flying at high speeds and thinking this large area is open for them to fly. When they don't realize that a large wide window-filled building was actually in front of the bird and didn't recognize it. They can disorient the bird, having to land on the ground and recover. In a case study, however, work has been done to compare the differences between buildings that have windows from the top down and compared the fatality rates of the sky-high buildings that are so window-filled as others. What they found was that "Collision numbers varied greatly among buildings..." Isolating factors that influence these fetal deaths among birds are quite difficult considering that some buildings might have vegetation or just be larger. Stadiums cover large lengths of an area instead of a skyscraper that goes for height, and it shows similar fatal collision rates. The urbanization of humans can be the only root cause due to habitat destruction and making it less viable for birds. Improvements can be made to include vegetation but have not shown much improvement.

It has been documented that most bird collisions tend to occur on lower levels of buildings that have large windows that reflect the abundant vegetation of green areas such as parks and gardens, creating the false illusion of a clear area.

Light Pollution

The building (on the right) shows the excess use of lights. This may appear as a problem for birds that are migrating.

A factor in which human infrastructures affected the bird's ecosystem is light pollution. Light pollution occurs when there's the use of excessive or unwanted light that can affect human or species' activities. In human infrastructures, there tends to be a ton of use of big, bright, and colorful lights to bring people's interest. In addition, New York is well known for the use of lights and big screens that brings attraction to tourists. However, humans are not the only ones that are intrigued by the lights. Lights have also gotten in the birds' line of site and distract them from flying straight. It has been shown that the use of excessive lights can disorient birds during migration. In a recent study, researchers Korner and Maravic conducted a series of surveys at night to detect the number of bird collisions on the Post Tower in Bonn, Germany around the fall season (from September 12 to November 1 of the years 2008 to 2013). The Post Tower is a 41-story building that illuminates colored lights all over the building during the night, which includes logos and emergency lights as well. After the survey period, they found that 1478 birds (at least 25 bird species) were affected by light pollution. This resulted about 107 casualties. However, through the course of their study, they saw a decrease in the number of bird casualties since the tower started to minimize their full use of lights with the use of shutters. The researchers saw the Post Tower as an example of how human infrastructure can decrease the bird demographics worldwide and that the reduction of light emissions was the key to preventing the alteration of the demographics. In conclusion, light pollution has been one of the major driving forces of a weakened bird ecosystem. Another study developed by Benjamin Goller​ and Bradley F. Blackwell wanted to test different lights that may trigger a response in cowbirds to avoid collisions. The researchers used different lights with increasing wavelengths. The wavelengths tested were 380-nm ultraviolet, 470-nm blue, 525-nm green, 630-nm red, and cool white. As a result, they found two significant results: light with 470 nm (blue) showed a 16 to 17 avoidance ratio and the light with 630 nm (red) showed a 13 to 17 avoidance ratio. However, they figured that light that have a 470 nm will be the perfect candidate to reduce bird collisions produced by light, since it produced the best results out of the other test variables. This shows that light pollution can be avoided for birds if humans take proper action.

Vulnerable Species

Studies on bird collisions with windows reveal a relationship between this event and specific bird species, indicating that some birds are more prone to collisions than others. This is due to morphology, flight characteristics as well as migratory routes. An example of this is that different species have different degrees of vision, as well as different flight patterns and speeds, ranging between species, and maneuverability during flight.

Among the species most affected are warblers, thrushes, sparrows, hummingbirds, and vireos, being the most susceptible the Blackpoll Warblers, bay-breasted Warblers, Red-eyed Vireos, and Ovenbirds. Although there is no clear answer as to why these species are more prone to these accidents, studies have shown that these species have a certain affinity and attraction for bright objects and illuminated structures, also these species are characterized by their rapid flight movements through areas with high vegetation and have great agility when maneuvering between trees, but this limits the ability to react if they become confused as often happens with some infrastructures.

Seasonality

Although many studies show an increase in bird collisions in winter, more focused studies show that the greatest number of collisions occur during spring and fall migration, being more noticeable in birds that passage-migrate birds. But in general, it is understood that there is an increase in the number of solutions during the fall and spring migrations as a consequence of the great displacement of bird populations as opposed to the constant urban change that cities undergo. In addition, deaths during the fall migration are significantly higher than in the spring, which is probably due to a higher proportion of young birds migrating for the first time.

There are no studies that provide continuous monitoring of bird collisions throughout the year and therefore these data may not be accurate.

Resolutions

Most states installed screens and grilles to ensure that birds don't confuse the reflective windows as their environment.

The Executive director of Audubon New York, Ana Tavares, pointed out that around three billion birds have been affected through the late 1900s. Due to the studies that have been found on human infrastructures, it was time to take action to reduce the damage brought on bird species. On December 10, 2019, New York authorities approved of the Proposed Initiative 1482B, which was a law that required infrastructures (such as buildings) to use materials that would prevent bird collisions. This proposal would change certain factors such as height, location, lighting, and the course of bird migration. A year later, the initiative influenced Washington D.C. to pass the Bird-Safe Buildings Act that required federal buildings to use bird-safe materials. As a result, the federal buildings installed screens or grilles on windows. In addition, the buildings reduced the use of glass windows on the lower floors, seeing that it can reflect the bird's surroundings. After Washington D.C., more than 20 states placed the law into effect to reduce bird mortality. Therefore, bird migration will be completely safe and will not bring any harm to their ecosystem. Another proposal offered by Audubon was to prevent the use of excessive lights during migrating periods.This is useful because this prevents the bright lights from disorienting them from their linear pathways. This also refers back to the research Post Tower, where the researcher found a decrease in causalities through the reduction of light usage over periods of time.