Hi everyone!

On the night of 11th of September every year (from dusk to dawn), two strong beams of light are shone onto the sky in New York, near the 9/11 memorial (9/11 Memorial & Museum). This art installation, Tribute in Light, honors those who died from the 9/11 terrorist attack on the World Trade Centre in 2001. However, Tribute in Light also resulted in an unintended consequence – the deaths of thousands of birds every 11th of September.

Perhaps the producers of Tribute in Light were not initially aware that the 11th of September coincides with the migration of birds across New York City. Moreover, most migratory movements are nocturnal (Van Doren et al., 2017)! Just like the dung beetles we discussed in the previous blog post, birds also require visual cues from celestial sources for navigation. Artificial light at night interferes with their ability to navigate well! Furthermore, the disruption to their internal navigational systems could lead to fateful collisions with buildings (Van Doren et al., 2017). In a research study conducted by Van Doren et al., “when the installation was illuminated, birds aggregated in high densities, decreased flight speeds, followed circular flight paths, and vocalized frequently.”

Photo: Van Doren et al., (2017)

 

What has been done to mitigate the problem? According to the New York Times, “when the number of trapped birds reaches around 1,000, the lights are switched off for 20 minutes to let the birds disperse” (Barnard, 2019). However, while this measure has prevented the deaths of many birds, is it enough? The study by Van Doren et al. also shows that turning off the lights led to a halt in behaviour disruptions. Yet what effects do those “trapped birds” suffer when the light beams are still on? And are there long-term consequences that could bear upon these birds? Could these circular paths taken by the birds also exhaust them of the energy they need to embark on their long-distance migration journeys?

Awareness of light pollution and its effects not just on humans, but on various life forms, goes a long way in ensuring that we make wise choices that will protect our ecosystems and health!

 

Sources:

Barnard, A. (2019). The 9/11 Tribute Lights are Endangering 160,000 Birds a Year. The New York Times, [online]. Available at https://www.nytimes.com/2019/09/09/nyregion/911-tribute-birds.html

Van Doren, B. et al. (2017). High-intensity urban light installation dramatically alters nocturnal bird migration. PNAS, 114(42), pp. 11175-11180.