Animals

It’s Not Time to Go Into the Light

Six months following the attack on the World Trade Center, the first Tribute in Light twin beams shot into the sky in commemoration of the lives lost on September 11th, 2001. However, it was only after a few years that the impact of these strong beams was brought into light. Apparently, the concentration of artificial lights induced a mass of birds to gather and circle within the beams, extending up to 4 kilometres skywards. Additionally, they were calling out and drawing even more birds into the light.

Statistically, the density of birds calculated during the Tribute in Light event was a shocking 60 to 150 times the value typically found in the area of lower Manhattan under normal circumstances. 

This following video captures the gathering of birds within the beams during the Tribute in Light and speaks of the effect of light on birds and how it is being managed. 

Impacts of ALAN on Migratory Birds

From the above example, it is evident that an effect of exposure to ALAN is the disorientation of migrating birds, which can result in fatal collisions. However, the impact of artificial lights on migratory birds is not limited to seasonal events which feature strong light concentration. Cities, in fact, are large polluters of concentrated lights and a huge threat to these birds. High fatalities of birds are recorded in the spring and autumn season during the migratory period of birds. Collisions of birds with buildings is also fairly commonplace. Approximately 100 million to a billion birds are killed in the United States annually as a result of such accidents. But why are migratory birds so attracted to light?

Naturally, birds are dependent on stars to illuminate their migratory path. In fact, they are capable of detecting lights on the horizon from great distances of hundreds of kilometres away. This article suggests that light pollution has gotten to the extent whereby no city in the Northeast of the United States where skyglow is undetectable by birds. In fact, an increasing density of birds was reported with closer proximity to these cities. With such light-sensitive abilities, it is no wonder that dazzling city lights have become a hindrance to their migration, causing them to instead be drawn towards the city and encircle lit areas. Such behaviours are problematic because the additional energy exertion of birds can over-tire and even kill already fatigued birds that have been flying hundreds of miles every night.

Magnitude of Problem

Sure, the death of birds is a serious issue, but I don’t see it as a problem in my city, so we’re all good right? Wrong. While it is true that the magnitude of bird fatality differs from city to city, it is essential to note that many cities conceal this problem as well. Many dead birds are swept off the streets at the break of dawn before anyone can see it. Case in point, this article speaks of the 90,000 to 230,000 annual bird deaths in New York City and how it is continually perceived to be a rare problem. To better understand the severity of bird fatality resulting from light pollution, the Global Bird Collision Mapper provides a glimpse of the distribution of bird collisions on a global scale. 

Till next time!

Trudie

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