Don Knowler returns home to the welcome sound of resident songbirds – and news of an avian crisis
A GREEN rosella sung a tuneful melody on my return from the Sunshine Coast this month, where I had travelled to escape the tail-end of winter. Together with my feathered friends, some of my other neighbours were also in tune as I made the rounds of my street to thank members of the Neighbourhood Watch for keeping an eye on my house while I was away, and the neighbour over the road who put out my bins for the refuse collection.
The notion of linking both feathered and non-feathered neighbours might seem fanciful, perhaps the result of a little too much alcohol consumed at Melbourne airport during a delay in the flight back to Hobart, but in my life avian neighbours are as vital a part of my suburban environment as the human ones. And such wild thoughts were reinforced by a news report I read the day after my return from Queensland.
In a story in the Mercury, ornithologists in the United States revealed that bird populations there were in crisis, with numbers falling by a third in the past 50 years amounting to an estimated three billion lost birds.
Listening to the melodious duet of a pair of green rosellas, and the sweet twittering of a scarlet robin, I envisioned what impact such a loss of birds would have on the birdrich Waterworks valley where I live. Bird lovers in the US are certainly noticing a feathered absence. And the silence in gardens is highlighting a problem that goes beyond just missing the beauty of birds in countryside and gardens.
A leading conservationist in the US state of Connecticut, Margaret Rubega, gives another perspective on the loss of birds which coincidentally corresponded with mine.
“If you came out of your house one morning and noticed that a third of all the houses in your street were empty, you’d rightly conclude that something threatening was going on,” she told an American news agency. Dr Rubega noted that the estimated three billion lost “neighbours” were the ones that protected human food supplies, by eating the insects that not only attacked crops but carried diseases that affected plants, animals and humans.
In the early 1960s, scientist and author Rachel Carson warned of a world without birds in her seminal work, Silent Spring, which dealt with the effects of chemical poisoning on wildlife. Since then the impact of harmful pesticides on birds and wild animals has been largely mitigated by tighter controls on pesticides like DDT but now bird lovers are faced with an even greater threat to birds. This is not merely confined to raptors at the end of the food chain, the main victims of poisoning by pesticides like DDT, but bird populations in general.
The threat this time, as the research is showing not just in North America but across the world, largely comes from habitat loss. In the US, ornithologists estimate the bird population of both the US and Canada was probably about 10.1 billion nearly half a century ago; since then it has fallen 29 per cent to about 7.2 billion birds. The researchers, detailing findings in the journal Science, projected population data using 13 bird surveys dating back to 1970 and computer modelling to come up with population trends for 529 species. The study did not take into account climate change. On the same day the North America report was published came another from Asia, revealing the caged songbird was threatening the populations of wild birds in parts of Indonesia. And scientists working on the island of Java calculated that the number of caged birds might now outnumber those in the wild. In Java, like much of Asia, most homes have a caged songbird, the birds often used in contests to judge the best singers. Although many birds are bred in captivity, wild birds are also trapped to fuel the bird trade.
The US survey, especially, struck a chord with me because it had its roots in the period I became a serious birdwatcher, buying my first pair of binoculars in the late 1960s.
At that time much of my bird-watching was confined to farmland in the rural area of Surrey where I grew up and over the past 50 years I have had first-hand experience of bird decline in the country of my birth, which to a certain extent is worse than that revealed in the US study. Those very areas where I learned my birding have seen declines in farmland species of more than 50 per cent, with previously common birds like the yellowhammer now difficult to find.
The loss of British farmland birds has been attributed to the advent of industrial farming, in which the weeds on which many birds – and insects – feed have been eradicated, and more intense crop rotations have not given ground-breeding birds a chance to rear young. In its widest sense, the prairie-style rangelands that have replaced the traditional patchwork of field and paddock can be construed as habitat loss, as destructive for wildlife as forest clearance or the draining and reclamation of marshlands.
The British experience is reflected right across Europe and, as with what is happening in both the US and Canada, holds a warning of what could happen in Australia if the question of vanishing habitat is not addressed. Australia might not have the same human population pressures of the rest of the developed world but surveys by BirdLife Australia reveal our bird numbers are also declining, with some species like Tasmania’s orange-bellied and swift parrots under the threat of extinction.
BirdLife Australia’s latest government-funded State of the Birds report, published in 2015, reveals that since 1990 the number of endangered birds has grown from 46 to 63, with three added to the critically endangered list in recent years. The latter include the eastern curlew, which reaches Tasmania at the far south of its migratory range. This has decreased by 90 per cent and there are fears it might vanish entirely from the state. Vulnerable species have grown from 59 to 63. Near-threatened have gone from 56 to 62.
Although habitat loss has been ascribed as the main reason for US bird decline, other factors are in play. A 2015 study said cats killed 2.6 billion birds each year in North America, while window crashes killed another 624 million and cars, 214 million.
But not all birds are in freefall in the US. Numbers of a much-loved neighbourhood species, the bluebird, are increasing, largely because Americans have made a special effort to protect these birds after noticing their numbers falling. Bird feed is put out in winter and nest boxes erected for these beautiful cavity-nesting birds.
Mercury, Hobart September 30, 2019