Buildings kill millions of birds. Here’s how to reduce the toll



These birds were killed by flying into a set of surveyed buildings in Washington DC in 2013.
USGS Bee Inventory and Monitoring Lab/Flickr

Norman Day, Swinburne University of Technology

As high-rise cities grow upwards and outwards, increasing numbers of birds die by crashing into glass buildings each year. And of course many others break beaks, wings and legs or suffer other physical harm. But we can help eradicate the danger by good design.

Most research into building-related bird deaths has been done in the United States and Canada, where cities such as Toronto and New York City are located on bird migration paths. In New York City alone, the death toll from flying into buildings is about 200,000 birds a year.

Across the US and Canada, bird populations have shrunk by about 3 billion since 1970. The causes include loss of habitat and urbanisation, pesticides and the effects of global warming, which reduces food sources.

An estimated 365 million to 1 billion birds die each year from “unnatural” causes like building collisions in the US. The greatest bird killer in the US remains the estimated 60-100 million free-range cats that kill up to 4 billion birds a year. Australia is thought to have up to 6 million feral cats.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


But rampant global urbanisation is putting the reliance on glass buildings front-of-stage as an “unnatural” cause of bird deaths, and the problem is growing exponentially.

In the line of flight

Most birds fly at around 30-50km/h, with falcons capable of up to 200km/h. When migrating, birds generally spend five to six hours flying at a height of 150 metres, sometimes much higher.

And that’s where the problems start with high-rise buildings. Most of them are much taller than the height at which birds fly. In Melbourne, for example, Australia 108 is 316 metres, Eureka 300 metres, Aurora 270 metres and Rialto 251 metres. The list is growing as the city expands vertically.

The paradigm of high-rise gothams, New York City, has hundreds of skyscrapers, most with fully glass, reflective walls. One World Trade is 541 metres high, the 1931 Empire State is 381 metres (although not all glass) and even the city’s 100th-highest building, 712 Fifth Avenue, is 198 metres.

To add to the problems of this forest of glass the city requires buildings to provide rooftop green places. These attract roosting birds, which then launch off inside the canyons of reflective glass walls – often mistaking these for open sky or trees reflected from behind.

Reflections of trees and sky lure birds into flying straight into buildings.
Frank L Junior/Shutterstock

A problem of lighting and reflections

Most cities today contain predominantly glass buildings – about 60% of the external wall surface. These buildings do not rely on visible frames, as in the past, and have very limited or no openable windows (for human safety reasons). They are fully air-conditioned, of course.




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Glass skyscrapers: a great environmental folly that could have been avoided


Birds cannot recognise daylight reflections and glass does not appear to them to be solid. If it is clear they see it as the image beyond the glass. They can also be caught in building cul-de-sac courtyards – open spaces with closed ends are traps.

At night, the problem is light from buildings, which may disorientate birds. Birds are drawn to lights at night. Glass walls then simply act as targets.

Some species send out flight calls that may lure other birds to their death.

White-throated Sparrows collected in a University of Michigan-led study of birds killed by flying into buildings lit up at night in Chicago and Cleveland.
Roger Hart, University of Michigan/Futurity, CC BY



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Want to save millions of migratory birds? Turn off your outdoor lights in spring and fall


We can make buildings safer for birds

Architectural elements like awnings, screens, grilles, shutters and verandas deter birds from hitting buildings. Opaque glass also provides a warning.

Birds see ultraviolet light, which humans cannot. Some manufacturers are now developing glass with patterns using a mixed UV wavelength range that alerts birds but has no effect on human sight.

New York City recently passed a bird-friendly law requiring all new buildings and building alterations (at least under 23 metres tall, where most fly) be designed so birds can recognise glass. Windows must be “fritted” using applied labels, dots, stripes and so on.

The search is on for various other ways of warning birds of the dangers of glass walls and windows.

Combinations of methods are being used to scare or warn away birds from flying into glass walls. These range from dummy hawks (a natural enemy) and actual falcons and hawks, which scare birds, to balloons (like those used during the London Blitz in the second world war), scary noises and gas cannons … even other dead birds.

Researchers are using lasers to produce light ray disturbance in cities especially at night and on dark days.

Noise can be effective, although birds do acclimatise if the noises are produced full-time. However, noise used as a “sonic net” can effectively drown out bird chatter and that interference forces them to move on looking for quietness. The technology has been used at airports, for example.

A zen curtain developed in Brisbane has worked at the University of Queensland. This approach uses an open curtain of ropes strung on the side of buildings. These flutter in the breeze, making patterns and shadows on glass, which birds don’t like.

These zen curtains can also be used to make windows on a house safer for birds. However, such a device would take some doing for the huge structures of a metropolis.

More common, and best adopted at the design phase of a building, is to mark window glass so birds can see it. Just as we etch images on glass doors to alert people, we can apply a label or decal to a window as a warning to birds. Even using interior blinds semi-open will deter birds.

Birds make cities friendlier as part of the shared environment. We have a responsibility to provide safe flying and security from the effects of human habitation and construction, and we know how to achieve that.


This article has been updated to correct the figure for the estimated number of birds killed by the cats in the US to “up to 4 billion”, not 4 million.The Conversation

Norman Day, Lecturer in Architecture, Practice and Design, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A hidden toll: Australia’s cats kill almost 650 million reptiles a year



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A feral cat snapped by a remote camera in the wild.
NT government, Author provided

John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Chris Dickman, University of Sydney; Sarah Legge, Australian National University, and Tim Doherty, Deakin University

Cats take a hefty toll on Australia’s reptiles – killing an estimated 649 million of them every year, including threatened species – according to our new research published in the journal Wildlife Research.

This follows the earlier discovery that cats take a similarly huge chunk out of Australian bird populations. As we reported last year, more than a million Australian birds are killed by cats every day. Since their introduction to Australia, cats have also driven many native mammal species extinct.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


We collated information from about 100 previous local studies of cats’ diets across Australia. These studies involved teasing apart the contents of more than 10,000 samples of faeces or stomachs from cats collected as part of management programs.

We tallied the number of reptiles found in these samples, and then scaled it up to Australia’s estimated cat population of between 2.1 million and 6.3 million. We also collated information from museums and wildlife shelters on the various animals that had been brought in after being killed or injured by cats.

We calculate that an average feral cat kills 225 reptiles per year, so the total feral cat population kills 596 million reptiles per year. This tally will vary significantly from year to year, because the cat population in inland Australia fluctuates widely between drought and rainy years.

On the hunt.
NT government, Author provided

We also estimated that the average pet cat kills 14 reptiles per year. That means that Australia’s 3.9 million pet cats kill 53 million reptiles in total each year. However, there is much less firm evidence to quantify the impact of pet cats, mainly because it is much more straightforward to catch and autopsy feral cats to see what they have been eating, compared with pet cats.

Binge eaters

According to our study, cats have been known to kill 258 different Australian reptiles (snakes, lizards and turtles – but not crocodiles!), including 11 threatened species.

The cat autopsies revealed that some cats binge on reptiles, with many cases of individual cats having killed and consumed more than 20 individual lizards within the previous 24 hours. One cat’s stomach was found to contain no less than 40 lizards.

Cat stomach contents, including several reptile parts.
Arid Recovery, Author provided

Such intensive predation probably puts severe pressure on local populations of some reptile species. There is now substantial evidence that cats are a primary cause of the ongoing decline of some threatened Australian reptile species, such as the Great Desert Skink.

By our estimate, the average Australian feral cat kills four times more lizards than the average free-roaming cat in the United States (which kills 59 individuals per year). But there are many more such cats in the US (between 30 million and 80 million), so the total toll on reptiles is likely similar.




Read more:
The war on feral cats will need many different weapons


The conservation of the Australian reptile fauna has been accorded lower public profile than that of many other groups. However, a recent international program has nearly completed an assessment of the conservation status of every one of Australia’s roughly 1,000 lizard and snake species.

Our research provides yet more evidence of the harm that cats are wreaking on Australia’s native wildlife. It underlines the need for more effective and strategic control of Australia’s feral cats, and for more responsible ownership of pet cats.

Pet cats that are allowed to roam will kill reptiles, birds and other small animals. Preventing pet cats from roaming will help the cats live longer and healthier lives – not to mention saving the lives of wildlife.


The ConversationThe authors acknowledge the contribution of Russell Palmer, Glenn Edwards, Alex Nankivell, John Read and Dani Stokeld to this research.

John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Senior Research Fellow, Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Sarah Legge, Associate Professor, Australian National University, and Tim Doherty, Research Fellow, Deakin University

This article was originally published on The Conversation. Read the original article.

Alien animals and plants are on the rise in Africa, exacting a growing toll



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The larger grain borer beetle attacks crops like maize and cassava, threatening food security.
Shutterstock

Katelyn Faulkner, University of Pretoria; Brett Hurley, University of Pretoria, and Mark Robertson, University of Pretoria

This article is the first in a series The Conversation Africa is running on invasive species.

Let’s say you’re travelling from Uganda to South Africa for business. You finally arrive at your hotel after a long day and decide to change before dinner. You unlock and unzip your luggage, but there’s something in your bag that you didn’t pack. As you reach for a clean shirt, a moth flies out. Did that come with you all the way from Uganda? It’ll be fine, right? Surely, something so small won’t cause any harm.

Species are intentionally or accidentally transported by humans between continents to regions where they are not native. With the help of humans or by natural means like flight, these alien species can also spread within continents.

Their spread within continents can be rapid, affecting both the ecology as well as societies and the economy. Unfortunately, it’s really challenging to prevent species from spreading. Given the vast amount of people and goods that are transported between and around continents they can easily be moved across oceans as well as between countries.

The spread of alien species within Africa is increasing. Since 2000 more alien insect pests of eucalyptus trees have spread to other African countries from South Africa, than have been introduced to these African countries from other continents. To manage the spread of these alien species countries need to co-operate, communicate and share information and skills..

The spread of alien species

Many alien plants and animals have been introduced to Africa from other regions and then have spread from country to country, often having devastating effects.

Take the larger grain borer beetle, (Prostephanus truncatus) which is thought to have arrived on the continent in imported grain from Mexico and central America. The beetle was introduced to Tanzania before 1984, Togo before 1981 and Guinea before 1987. It then spread across the continent and within 20 years could be found further south in South Africa.

The beetle attacks crops such as maize and cassava, threatening food security and the livelihoods of the poor. Infestations often destroy maize that’s been stored by farmers, forcing them to buy maize as well as lose income they could have earned from selling any excess.

But alien species don’t just arrive from abroad. Many that are native to parts of Africa have also spread to countries on the continent where they are not native.

An example is the fish commonly known as the Mozambique tilapia (Oreochromis mossambicus) which is native to rivers on the east coast of southern Africa. Fishermen have transported the Mozambique tilapia to other areas and it is now found in river systems in southern and western South Africa and Namibia.

The Mozambique tilapia is a popular species for fishing but it can pose a threat to native fish and has been responsible for the disappearance of native species in some regions.

The spread of alien species within Africa is by no means a new thing. For instance, the bur clover (Medicago polymorpha), a plant from northern Africa, might have been accidentally transported by humans to South Africa as early as 760 AD.

A high and increasing threat

Recently a number of alien species have spread extremely rapidly across the continent, posing a particularly high threat to food security and livelihoods.

The fall armyworm, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.
Shutterstock

One is a caterpillar known as the fall armyworm (Spodoptera frugiperda). The species, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.

The moths of the armyworm are strong fliers and the species may have spread through flight to South Africa from other African countries. Although the species attacks a wide range of crops, it poses a particularly serious threat to grain farmers. It is extremely difficult to manage.

Another example is a wasp known as the bluegum chalcid (Leptocybe invasa), which is native to Australia. In 2000 it was detected in Israel and shortly afterwards it was reported in Uganda and Kenya. From there it spread rapidly to many African countries including Zimbabwe, Mozambique, and Tanzania and was finally detected in South Africa in 2007. The insect probably reached Israel on live plant material and spread into Africa the same way, or was carried by people travelling between countries.

The wasp causes swelling or growths on eucalyptus trees, which can lead to decreased growth and tree death. As eucalyptus trees are an important source of income and fuel, this species could have an impact on the livelihoods of locals in these countries.

Preventing the introduction and spread

Once a species is introduced to one African country it’s highly likely it will spread to others on the continent because borders checks are weak.

The introduction and spread of species could be reduced if countries introduced biosecurity systems. These are used extensively in countries like Australia and New Zealand and involve using technology to check for alien species when people and goods enter a country. In Australia this involves inspecting goods, vehicles and luggage before they enter the country.

But even these systems aren’t a guarantee that species won’t spread. African countries would need to work together and share information and skills. This would also allow countries to prepare for the arrival of species, and to draw up plans to reduce their impact.

The ConversationThis is a tall order. But as a country’s defence against alien species introductions is only as strong as that of its neighbours, such action would benefit all of the countries involved.

Katelyn Faulkner, Postdoctoral research fellow, University of Pretoria; Brett Hurley, Senior Lecturer Zoology and Entomology, University of Pretoria, and Mark Robertson, Associate Professor Zoology & Entomology, University of Pretoria

This article was originally published on The Conversation. Read the original article.