Posts Tagged Birds
Monday 28 April 2014 4:52PM
Up to 80 per cent of Australian households are involved in some kind of bird feeding. So are we creating a generation of bird bludgers dependent on handouts? Associate Professor Darryl Jones takes a look at the science behind backyard bird feeding.
It’s a most unlikely setting for a heated national controversy. Some regard it as misguided and even dangerous. So what is 83-year-old Mrs Rosine Jennings up to that raises such ire from her neighbours and critics beyond?
Every morning a little after dawn, Mrs Jennings carefully prepares a platter of cheese pieces, German sausage and diced heart which she places on a small platform on the balcony of her inner suburban Brisbane apartment. Cup of freshly brewed English Breakfast tea in hand, she sits a few metres away, awaiting her special visitors: a pair of magpies. They usually arrive within minutes. ‘Isn’t it marvellous!’ she declares. ‘Nature, right here in the middle of the city—and to think that some people say that it’s wrong!’
In this instance, ‘some people’ refers to Jack Miller from the neighbouring apartment. In Mr Miller’s forthright opinion, Ms Jennings is ‘a right nutter’.
‘These birds are all common,’ he says. ‘They don’t need any help. And all this feeding is doing is making the bloody things dependent on handouts! It’s a disgrace!’
Mr Miller and Ms Jennings represent two sides of the fence in what is a very Australian controversy: the feeding of wild birds. It’s a peculiar dilemma in this country because, although the sanctions are unofficial and informal, everyone seems to be aware that it’s not really acceptable. There are many reasons for that: the types of foods are wrong, it spreads disease, it encourages the wrong species; and, most prominent of all, feeding leads to dependency on human-provided foods.
These concerns are familiar to feeders the world over. What is interesting is that the negative is unquestionably the predominant perspective in Australia. We all know we shouldn’t feed, and this makes us truly unusual in terms of bird conservation and welfare. In the Northern Hemisphere, the clear message is that the feeding of birds is both kind and good. Indeed, all the major bird and conservation organisations—the British Trust for Ornithology and the Audubon Society, as prominent examples—actively and passionately advocate the feeding of birds, and claim it as the act of any genuine conservationist: ‘If you care about birds, feed them!’
That message has clearly been heeded; a range of surveys of wild bird feeders in North America and Europe show that between 45 and 75 per cent of households are actively engaged in feeding birds at home. Australians, with the ‘feeding is bad’ message ringing in our ears are apparently different from the rest of the world. This was noted with some fascination by British ornithologist Andrew Cannon in a paper on gardens as places for bird conservation. He quotes an undisclosed Australian source as saying: ‘Generally, the more conservation-minded and knowledgeable individuals in Australia do not feed.’
What is truly remarkable about this summation of our national position is not so much the attribution, but the fact that it is so fundamentally wrong. For despite the clarity of the anti-feeding message here, the reality is that the participation rate is about the same as everywhere else. A number of surveys found that between 38 and 80 per cent of households spend their hard earned cash on attracting birds to their backyards. The question is why.
At the most mundane level, many birds are thoroughly adept at spotting foraging opportunities. Discarded food scraps will often attract an eager scavenger. And once these animals are noticed, an almost innate reaction seems to be offer a little something: a few chips for the seagulls, sandwich crusts for the ducks. You can see such public interactions in parks or picnic grounds the world over—with or without ‘don’t feed the wildlife’ signs.
It is, however, somehow different when the interaction is in the private intimacy of one’s backyard. By intentionally offering food to attract wild birds to our back yards, we seem to be seeking something more than a casual encounter. Inviting wild birds to share our table suggests something potentially deeper. For some it’s just a chance simply to see beautiful birds up close; for others it’s a heart-felt assistance to apparently hungry birds. And it can also be a profoundly personal experience—a way of connecting with nature.
A few years ago, my colleague Peter Howard and I studied the motivations of bird feeders in Brisbane. Among the most powerful explanations offered by the people we interviewed was what we academically labelled a form of ‘environmental atonement’. Humans had caused so much damage to the natural world, these people explained, that feeding the wildlife was one way of giving something back, a personal attempt to redress the balance. This powerful component of the feeding story has since been identified among feeders throughout the world. Feeders feed for a variety of different reasons, but many care strongly about their birds, and some, at least, do so for broader conservation reasons.
And caring is probably how it all began. In the harsh winters of the Northern Hemisphere the plight of those clearly vulnerable creatures was all too obvious. Offering crumbs to starving robins in the snow would always have been commonplace, a humane gesture to helpless victims gathered at the back door. Slightly more elaborate homemade concoctions such as suet or peanut balls have been widespread in North America and Europe for a least the last couple of centuries. But that was the offering of familiar items from the domestic kitchen, only in winter. Today, all that has changed dramatically.
Beginning in the prosperous post-war decades, a specific and dedicated industry developed to serve and promote the feeding of birds. This has been most evident in the UK and US. The bird seed industry is currently worth over a US$10 billion. American households now distribute over 500,000 tonnes of seed to suburban birds annually. In the UK alone, enough seed is offered to support 30 million great tits, about six times the actual population of the species. There is also now a distinct push from the industry—but also from key bird and conservation organisations—to feed year-round.
A big part of this stems from conservation perspectives. It is argued that anthropogenic feeding supports populations of species which would otherwise be in worse shape. This has some support in places like the UK, where the single-most important bird habitat is now domestic gardens. There is strong evidence that some threatened birds—such as the song thrush—are surviving substantially because of human-provided food.
But this special case only highlights the stark reality that almost all wild bird feeding advantages the species which are already present and doing well. This is as true in Birmingham and Seattle as it is in Ballarat and Newcastle. Although Australians do feed birds on farms and in regional townships, the overwhelming majority of feeders live in the suburbs of our larger cities. This means that the birds that are potentially available to visit our backyards have already been through the filter of urbanisation. Although there will always be local exceptions, it is highly probable that the species most likely to visit your feeder will be big, aggressive, generalists that have long discarded their innate fear of people. These are the characteristics associated with success in the strange artificial landscape of the urban environment. Put out seed in whatever your city and I predict rainbow lorikeets, crested pigeons and possibly cockatoos; if it’s meat or cheese, expect magpies, butcherbirds and kookaburras.
Which brings us back to Mr Miller and Ms Jennings and their endless arguments; for one, the provision of food is an attempt to get close to wild creatures and possibly assist their welfare. For the other, it’s a potentially dangerous and selfish pastime. So surely, this is simply a matter of collating the evidence and settling this so-called controversy like scientists.
However, the unexpected dilemma for us is that although bird feeding is an immensely popular pastime practiced daily by millions of people all over the world, almost nothing is known about what all it’s doing to the birds. Because all of the food provided is entirely additional to their normal diet, this activity has been described as a ‘global supplementary feeding experiment’. It is an experiment in which the millions of participants are all focused on their own patch, thoroughly unaware of their potential influence on the wider landscape.
What we can say with some confidence, based on a large body of experiments on wild birds, is that even a little extra food leads to earlier breeding, more chicks, and a greater chance of surviving to the next year. In other words, feeding typically results in more birds.
That research, however, tells us rather little about the other concerns associated with bird feeding. What we can say is typically tentative. Sure, certain diseases can be spread as birds crowd at feeders, but given the colossal numbers involved, these outbreaks are very rare indeed. Certainly, some types of foods, like bread, are inadequate and potentially harmful. But for most birds, the proportion of their overall diet made up of human-provided food is so small that little harm is likely.
And is all that artificial food leading to a nation of, as has been put to me innumerable times, a bunch of bird bludgers? The genuinely good news is that there is no evidence of widespread reliance on the food we provide. Almost all species investigated still find and consume a diet dominated by natural foods, and only visit to our bird tables for snacks.
Whether you like it or not, millions of Australians feed birds. This is almost certainly changing the avian landscape, but they are not going to stop. The best we can hope for, at least until more explicit research is undertaken, is for feeders to follow some simple guidelines like keeping their feeding areas clean; avoiding bread and processed meats and not putting out too much. Consider this: the birds don’t need it as much as you do.
Ockham’s Razor is a soap box for all things scientific, with short talks about research, industry and policy from people with something thoughtful to say about science.
Fred Grimm: Miami-Dade’s trap-neuter-release program utterly ignores science – Miami-Dade – MiamiHerald.com
So says a current television commercial trying to convince drivers to slow down. A recent study indicates that this will save not only human lives but avian ones as well. It seems that birds are able to calculate the average speed that cars travel along certain stretches of road and adjust their flight initiation distance accordingly (http://www.sciencenews.org/view/generic/id/352603/description/Birds_know_road_speed_limits).
On stretches of road with a speed limit of 20 kilometres per hour, birds waited to fly until the car was about 10 metres away. That distance increased to roughly 25 metres on roads with a 90 km/h limit and around 75 metres at a 110 km/h limit. Consequently a speeding car will reach the bird earlier than it expects, making it more likely to be struck. Yet another reason to slow down and stick to the speed limit.
Over the years I have seen many avian road trauma victims. Recently I have begun peering into the eyes of these injured birds. Intriguingly a number of them have long standing retinal damage presumably reducing their visual acuity and field of vision. I wonder if many of the birds that are struck on roads become victims because their eyesight is compromised. To study this properly I would need to compare the injured birds with a sample of healthy wild caught birds. Something for the future.
Dr. F. Bunny
Legagneux, P., and S. Ducatez. 2013. European birds adjust their flight initiation distance to road speed limits. Biology Letters. Published online August 21, 2013. doi: 10/1098/rsbl.2013.0417.
In a world of climate change we are all (well, maybe not the coal and oil companies) looking for alternative ways to generate energy that do not produce greenhouse gases. It seems ironic that the nuclear industry has seen this as a potential opportunity to appear green and a viable alternative to coal power. Apart from the fact that plutonium is still deadly for 250,000 years and countries like Germany appear to be winding their nuclear programs down in the wake of the Fukushima disaster, nuclear is no more sustainable than coal or oil. Uranium will run out just like all the fossil fuels, so why go down a potentially lethal path for the sake of a few years of power? Forget the nuclear nonsense and head straight to the technologies that will keep my computer alive and active long after I’ve nourished a few thousand worms.
Which brings me to wind farms and turbines. As usual, a lot of nonsense is being spouted by both sides. One memorable newspaper article described opposition to turbines because they would negatively affect the migrating orange-bellied parrot, with a lovely full colour photo of the parrot accompanying the article (http://www.theage.com.au/articles/2006/04/05/1143916574751.html). Interestingly these turbines were destined for a site east of Melbourne, in an area not visited by OBPs, who prefer the saltmarshes west of Melbourne for their overwintering grounds.
Nevertheless turbines do kill birds and bats, 100,000 to 440,000 birds each year according to the US Fish and Wildlife Service (http://www.nature.com/news/the-trouble-with-turbines-an-ill-wind-1.10849), generally through direct collisions. This is, however, considerably fewer than are killed by cars (60-80 million), building strikes (100,000 to 1 billion), power lines (up to 175 million) and our old friend, the pussy cat (365 million to 1 billion). Very rubbery figures to be sure, but significant nonetheless.
Bats, however, die in a more interesting way. The movement of the propellers generates a significant area of low pressure behind the turbine (five to 10 kilopascals less than the surrounding air). As nature abhors inequality, when the unsuspecting bat flies into this low pressure region the relatively higher pressure inside its body attempts to equalise with the lower pressure outside its body. It does this by expanding outwards, which leads to ruptured blood vessels and lungs filled with blood (http://www.scientificamerican.com/article.cfm?id=wind-turbines-kill-bats). I can certainly attest to this, having necropsied affected bats. There are no external signs of damage but their chests are certainly full of blood, caused by this barotrauma.
What to do? Do we sacrifice some birds and bats on the altar of climate change, because none of us want to return to pre-electricity days but we also don’t want our planet to heat up? You can’t make an omelette without breaking eggs, and all that. Rather than scrap a potentially important source of sustainable power one suggestion is to be smarter about placing wind turbines away from bird and bat flight paths in the first place. While this is sensible in principle we don’t know enough about their pathways to make this work reliably.
What shows more promise is redesigning the turbines themselves. On a recent ski trip to Copper Mountain in Colorado I saw some wind turbines on the very top of the mountain. But these turbines were different to the traditional horizontal axis turbines we are all familiar with. They were vertical axis turbines. Instead of having a big propeller spinning on a pole, they had vertically orientated blades which spun around the central pole. I had never seen this design before, but it could be the answer. According to a report these vertical turbines are less dangerous than the horizontal ones because they don’t use propeller-like blades to capture the wind, but rotating open-framed cylinders (http://www.msnbc.msn.com/id/44627832/ns/technology_and_science-innovation/t/upright-turbines-breathe-new-life-wind-farms/). The downside is that they don’t generate as much electricity as the traditional turbines. However, according to the article, “putting windmills upright and spacing them more tightly together can generate more electricity on less land, and kill fewer birds or bats than traditional horizontal rotating wind turbines.” These vertical turbines are also only 30 feet high, which is below the migratory level for birds and bats.
It is amazing how resourceful we can be when we have to. It’s just a shame that resourcefulness only materializes when we are faced with a catastrophe. But that is how we operate, I guess. Why waste time on things that might happen, like Y2K, when there are so many things that are happening to worry about? It does make preventative medicine particularly hard to sell, however.
Dr. F. Bunny