Collisions with windows are a growing threat to bird populations. Can technology come to the rescue?
MOST OF US HAVE experienced it at some time – the distressing thud that signals a probably fatal collision of bird and window. Such occurrences are a growing conservation concern; window collisions kill more birds than any other human-related factor except habitat destruction. Estimates suggest the number of birds killed like this globally each year could be in the billions.
Australian ornithological consultant Stephen Ambrose has spent almost two decades advising councils, architects and developers on how to improve building design to reduce the risk of bird strikes. Collisions, he explains, are mostly caused by birds trying to reach habitat they can either see through the window or reflected in it.
He adds that migratory species are particularly at risk, although the precise impact bird–window collisions are having on Australian species has yet to be studied in detail. One exception is the critically endangered swift parrot, the only bird species known to be adversely affected by window-strike mortality at the population level.
As its name suggests, the swift parrot is a fast flyer, typically travelling in flocks as it migrates from Tasmania to the south-eastern mainland of Australia. It tends to fly at or below tree-top level, which puts it at particular risk of window collisions.To make matters worse, its favoured mainland habitat is forested areas, and these happen to be where more and more homes are being built, increasing the chance of collisions.
It has been estimated that each year up to 2 per cent of the swift parrot breeding population – which is down to a mere 2000 or so birds – is killed as a result of collisions with windows, fences (especially chain-link fences) and vehicles.
ANOTHER SPECIES attracting concern is the powerful owl, which is threatened in New South Wales. “Recently there has been a significant increase in the number of
powerful owl strikes in Sydney,” Stephen says. Again, the encroachment of residential development into bushland is exacerbating the problem.
Stephen is also concerned that “multiple high-rise buildings are being built near internationally important wetlands in major cities and towns in Australia”.This trend is likely to lead to an increase in incidents such as the one that saw an immature white-bellied sea-eagle killed in Sydney’s CBD after it collided with a tall building.
Disappearing natural habitat is also driving more birds into urban areas – a process that’s accelerated by our efforts to attract them. “Australians love landscaping their gardens, feeding birds and providing water baths for them,” Stephen says. “This, in turn, attracts birds to people’s gardens, which is fantastic.” The downside is that drawing birds into an urban environment increases the likelihood they’ll fly into a window at some point.
It’s not only windows that are a problem. Barriers erected to shield residents from the noise of busy roads are also a major issue. “There are reports of birds, especially parrots, smashing into the glass or fibreglass barriers in an attempt to reach the trees on the opposite side of the road,” Stephen explains.
“As a result, road architects and engineers now construct road barriers that are visible to wildlife.”
Stephen believes that attempts to reduce bird–window collisions are slowly gaining momentum in Australia. “Most architects and engineers are quite receptive to modifying their designs or using different building materials to reduce the risk, if it’s explained logically and sensibly,” he says. “It usually just involves tweaking things here and there, rather than major redesigns, which makes it easier to gain the support of the builders.”
There is still much room for improvement, however, particularly in regard to the design of major buildings in Australia’s cities.
“Many new high-rise and other large city buildings have lots of glass windows, and plaza areas are often landscaped with canopy trees and shrubbery,” Stephen says. “While many of these designs are aesthetically pleasing, they do increase the risk of birds striking glass panes.”
Barriers shielding residents from the noise of busy roads are also a major issue.
Birds flying into windows usually strike head-first, resulting in concussion or a broken neck.