Hundreds of dead birds picked up in a morning at the base of 1, 3, 4 and 7 World Trade Centers

The World Trade Centers (WTC) are proving fatal to migrating birds. The topic is of interest to cat advocates due to cat predation on birds. But what if cats are eating the birds killed when they fly into buildings? Cats have difficulty in catching birds which is why they are a relatively small part of their diet.

There are volunteer bird collision monitors around the WTC buildings. Migrating birds become confused at the reflections in the glass and fly in to them. They are killed by the impact and fall to the ground. Volunteers pick them up from the sidewalk like litter. Many are not picked up because they are inaccessible; numbers reported are not comprehensive.

One volunteer working for the bird conservation group New York Audubon, Melissa Breyer, tweeted that she had picked up 226 dead birds on September 14, 2021. However, she said that many other birds had been swept up and were inaccessible or too mangled to collect. On Tuesday morning she found almost 300 dead birds at the bases of one, three, four, and seven World Trade Centers.

She said that she was shocked and overwhelmed. “I looked around and it was like a nightmare”. She tweeted photographic records of the birds, one of which you can see below. She worked for 65 minutes, only, saying that she did “one loop around @4WTC and @3NYWTC — most of these before sunrise. Please can we turn off lights during migration???”

That’s a reference to numbers 4 and 3 World Trade Center. The video shows her quite rapidly picking up dead birds on the sidewalk as if they had come raining down from the sky. She asked for action to be taken.

Birds killed by flying into World Trade Center NYC one morning. Many were not picked up and photographed.

“When you have 226 dead window-struck migratory birds from one morning, it’s hard to get them all in one photo”. Birds killed by flying into World Trade Center NYC one morning. Many were not picked up and photographed. Photo: Melissa on Twitter.

It seems likely that many thousands of birds have recently been killed by these buildings. They want something done. A spokesman for number one World Trade Center, Jordan Barowitz, said: “The first 200 feet of One WTC are encased in glass fins that are non-reflective. This design was chosen because it greatly reduces bird strikes which mostly occur below 200 feet and are frequently caused by reflective glass.”

So, something had been done but clearly not enough. Turning off the lights at night can help. The problem appears to be partly caused by a “big pulse in migration” and not the 9/11 celebrations over the weekend when the lights were on.

Decals have been it stuck to the glass of a see-through barrier in Liberty Park in Manhattan after dozens of songbirds crashed into it.

Note: This is an embedded tweet. Sometimes they are deleted at source which stops them working on this site. If that has happened, I apologise but I have no control over it.

The bird predation context

The reason why this is of interest to me is because domestic, stray and feral cats get very bad publicity about predation on birds. But we know that across the United States, and of course in other countries, millions of birds are killed by buildings. An estimated up to 1 billion birds die annually in the USA from window strikes. An estimated 2.4 billion birds are killed by cats in the US per year. Although, we have to be cautious with numbers. They are estimates. I’m particularly cautious about the estimated cat predation kills.

The authorities don’t know how many feral cats there are in the US. I’ve seen big disparities in numbers. If you don’t know the number of cats there are in the country you don’t know how many birds are killed by them. Estimated figures are normally too high in my honest opinion. I suspect that the estimated bird kills from flying into windows is too low judging by the stories from the volunteers working around the World Trade Center buildings. They are picking up a fraction of the total number. Also, many of the studies or surveys done on bird strikes on buildings were carried out by developers or other interested and concerned parties. Are they accurate when carried out by developers?

Domestic cats ‘kill’ dead or dying birds

A study dated 2 January 2014 estimated that between 365-988 million birds are killed annually by colliding with buildings in the US. They do state that “no current U.S. estimates are based on systematic analysis of multiple data sources”, which implies to me that the estimate provided is inadequate and falls short of the true total.

Google Scholar has many articles about how to prevent bird strikes on buildings. Clearly more work needs to be done at this building complex in New York to prevent bird deaths. It surprises me that not enough was done initially. Other man-made structures also kill birds such as wind turbines.

The conclusion I wish to come to in this article is that more work needs to be done on working out a true figure of the number of birds killed by buildings in the USA. I’m defending the cat because I think that the true figure for buildings may be in the same order as the estimate for cats.


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Michael Broad

Hi, I'm a 74-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I love nature, cats and all animals. I am concerned about their welfare. If you want to read more click here.

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