The Science of Songbirds

We’ve remarked many times on this programme that the world is producing a lot of plastic waste. Millions of tonnes of it per year. And if you look at “plastic per person”, the UK is a major culprit. Now you might think - that’s OK - because we have recycling in the UK for plastic cartons and bottles! But - a new report from the charity Greenpeace says that’s not solving the problem - because a lot of it is being sent abroad. The report claims that well over half the plastic we think gets recycled is exported to countries like Turkey, where it mostly just gets dumped. When investigators travelled to Turkey, the scenes they discovered were truly shocking. Phil Sansom spoke to Greenpeace’s Sam Chetan-Welsh...

Sam - What we found is widespread and extensive evidence of UK supermarket plastic being dumped and burned in southwest Turkey. Tesco cheese packets, yoghurt pots... we found piles of it on fire, causing breathing problems for people in the local area; we found the rubbish leaking into watercourses, into streams, into rivers, and that will eventually make its way onto beaches and into the Mediterranean.

Phil - This is really shocking! How on earth is rubbish from UK supermarkets ending up by the side of the road, burning, in Turkey?

Sam - It's a complicated story. And I would give a big caveat that this is a very complicated system, it's very opaque, there's a lot of crime and illegality. The best that we as Greenpeace can surmise about what's happening is: say you've got your milk carton or your yoghurt pot. You wash it, you put it in the recycling. What happens then is it goes to a Materials Recovery Facility, and that's where it gets sorted into waste that's clean enough to actually be mechanically recycled again, or it gets baled up with what's called mixed plastic waste. What we found is that a lot of the clean stuff is going into big containers to be exported, and then mixed up with all of those mixed bales of plastic waste. And then it gets sent off to countries like Turkey.

Phil - Are UK companies paying the people to transport it to Turkey? Or they selling the waste so that the people in Turkey can get the good stuff out, and maybe make a buck off that?

Sam - There are layers of different people paying different types of money. The supermarkets, for example - they do pay, because they buy these certificates to kind of confirm, "hey, I'm Tesco, I'm Coke, I've made this much plastic this year so I need to pay for this amount to have it recycled." The issue with that is - there's no checks on the Turkish side, so it's a lot cheaper for companies through this chain to pay for it to be exported. At the Turkish side, for example, it will be bought by a company who can then make money off extracting the valuable material from these mixed, contaminated bales, and then essentially - on the hush hush - dumping all the rest of it.

Phil - Is that how this is going wrong, then - that people on the UK side are just abandoning their responsibility by giving away the plastic and saying, "all right, I'm sure you're going to recycle it." And the people who take it go, "sure thing, yeah, I'll do that," and then just do whatever they want.

Sam - Yeah. There's widespread fraud and corruption within the system, which is a big problem. But really Greenpeace's diagnosis is that at the heart, even if you improved enforcement and monitoring, you'd never really be able to fix the problem because there's just too much stuff. There's just too many containers. Too much of it is non-recyclable. No-one's got a plan to reduce the amount of waste that we produce in the first place, and that is how you stop this problem. We always think of it like - imagine a bathtub. If your bathtub was overflowing, you wouldn't grab a mop and bucket, you would turn the tap off. And that's what we need to do with the waste system - deal with the waste that's arising at the beginning of this process. That's the only way you're ever going to fix it.

Phil - Right, but how big is the problem? Is this just a small issue that's only part of the plastic that I'll put in my recycling bin, or is it the majority?

Sam - The UK exports two and a half Olympic-sized swimming pools of plastic waste every single day. That is not a small problem; that is something that we need to take responsibility for. Greenpeace estimates only 10% of all UK household plastic packaging actually gets recycled here in the UK. But look - ultimately, in our view, a kilogram of exports being dumped on another country, on a poorer country, on communities of colour to deal with, leaking into their watercourses, causing breathing problems in their local communities, is completely unacceptable - never mind two and a half Olympic-sized swimming pools of plastic every single day. This is something we need to take responsibility for. Government has been relying on this as part of their waste policy for such a long time. Plastic waste exports have increased by sixfold since 2002. And what we're saying is: stop dumping our waste on other countries, stop relying on this to deal with waste that we should be cleaning up ourselves, firstly by reducing the amount of plastic that we make and use here in the UK.

Phil - I mean, what am I to do as just someone who tries to recycle? Is this plastic recycling system broken?

Sam - What I really don't want people to take away from this is that they should stop recycling, that they should give up, that they should be cynical about the system, that they shouldn't keep doing their bit - because that habit is going to be crucial for us in the future, the habit of washing stuff and doing the right thing. But recycling on its own is never going to be able to solve this problem. We are simply making and using far too much stuff.

The COVID pandemic has brought into sharp relief the toll working long hours takes on your mental and physical well being. Now, scientists at the WHO have managed to put numbers to the problem - by combining data from a global, 10 million person survey with reports from countries around the world about causes of death, they’ve calculated that 745000 people died in 2016 due to stroke or heart disease caused by working longer hours. Lead author on the study Frank Pega from the World Health Organisation spoke with Eva Higginbotham...

Frank Pega - Forty professors from around the world looked at a number of different categories of long working hours. And when they crunched the numbers and looked at all the available evidence, they found that there was strong evidence that when people work 55 hours or more per week their risk for chronic heart disease and stroke is increased. And indeed that's very common in health science. And we talk about a risk limit here.

Eva Higginbotham - What's the mechanism, or what's the link between working long hours and having a stroke or having heart disease.

Frank Pega - The first link is in a way, a direct pathway where people who work long hours and all of us who have worked long hours or know somebody who's worked long hours has experienced this, basically feels stressed. Our body has a physiological physical response to working long hours. It releases stress hormones, and these stress hormones directly damage the heart or the brain and thereby they can directly produce heart disease or stroke. A second pathway through which long working hours can cause these diseases is by them increasing other risk factors for heart disease and stroke. So for example, people who work long hours may as a result also be more likely to smoke or to drink alcohol or have sleep deprivation. This in turn could then cause heart disease or a stroke event.

Eva Higginbotham - Is this true for all kinds of jobs or just for jobs that we might traditionally think are very stressful? I'm thinking things like manual labour or people who are like CEOs, running big companies who are under high stress and work long hours?

Frank Pega - We've done some analysis to look at the available data that is broken down by occupations and by industrial sectors. This is how we divide the world. And we found that everybody who works long hours seems to be at the same level of increased risk in as far as the evidence is currently available.

Eva Higginbotham - I'm wondering if there's an age factor here because people will sometimes say, you know, work hard in your twenties, your thirties, your forties, and then you'll be able to relax when you're older. Do we know if working long hours at any stage in your life is damaging or is it just later or just earlier?

Frank Pega - We did not see differences in risk across age groups. In other words, if you're working long hours when you're 20, or if you're working long hours when you're 60, makes very little difference for your actual increase in risk of having a cardiovascular disease or stroke event. However, what we do notice when it comes now again to the number of people dying of cardiovascular disease, so heart disease, stroke, is concentrated specifically amongst middle aged and older people. So when we ran our estimates and we did our modelling, we found not surprisingly that more people died from long working hours in these middle aged and older working age groups than younger people did, but to be clear the risk's the same.

Eva Higginbotham - And is this a global problem? Did you find that there were some places that had a higher resulting risk from longer hours versus others?

Frank Pega - So what we found is that when we looked at the distribution of the number of deaths, for example, from these two conditions, from stroke and heart disease, that these were particularly high in two regions in the Western Pacific region, and in Southeast Asia. There were other regions where the numbers were much lower, for example, in Europe and also in North America. So there's clearly a geographic patterning.

Eva Higginbotham - Is that because there are more people in those regions who work those hours or the type of work that they're doing, or other factors in their lifestyle, do we know?
Frank Pega - One part of the puzzle and one part of this explanation is that there's definitely a higher proportion of people working long hours in these regions. And if you ask why that is, one reason is that these regions have a number of low and middle income countries, for which we know that a large proportion of the workforce of people working are in an informal economy. So they do not have a formal employment contract. That means often these are workers who are disadvantaged, so they may not have a choice, but work multiple jobs at a time, which of course means clocking more and more hours.

Eva Higginbotham - What can we do to try and stem this problem?

Frank Pega - We recommend four arms of action. First, laws and policies to be put in place by governments, but also employers and workers to limit numbers of hours of work per week to healthy limits. The second area of intervention would be to make sure that working time arrangements are more balanced. For example, workers can be offered working time or can be working on flexi time. The third intervention, and this is very important for workers in the informal economy, so those without formal employment contract, they are not covered by the protections of social security and employment that are normally offered to work as in the formal economy. So here we need to, countries are encouraged to offer social protection floors. These are antipoverty programs which enable these workers to not have to work long hours and multiple jobs in order to survive. Fourth, and finally, we recommend that all workers have access to occupational health services where occupational health physicians can make sure that the numbers of hours worked stay below the unhealthy limits.

Once birds make it out of the nest, songbirds have to set about learning their songs. Some birds, like parrots, are called “open-ended learners” because they can continue learning more and more sounds over their lifetimes. But others, on the other hand, have only a specific period of teenagerhood where they learn their songs, and zebra finches are an example of this. Mimi Kao, at Tufts University, studies how this happens, and spoke with Chris Smith...

Mimi - Well, vocal learning in songbirds shares many similarities with vocal learning in humans, and it occurs in two phases. In the initial sensory phase of learning, birds are just listening, and they're forming an auditory memory of an adult tutor. And then in a second phase, known as sensory motor learning, they begin to practice. And the sounds that they make first are quite variable, much like the babbling in human infants, but they're listening to themselves as they're singing and they're trying to correct it. And so they continue practicing thousands of times a day until they're able to make an accurate copy of the tutor song.

Chris - Why teenagerhood, why don't they do that from the get-go?

Mimi - Well, initially the areas of the brain that are important for producing songs are not totally wired up. So the connections aren't there yet. The auditory areas are there and functioning, so they're listening, but around 25 or 30 days those connections from the song motor region form the connections with the next region and the birds begin to vocalise.

Chris - Interesting that it's the adolescent period of their life, and we're very familiar with human adolescents, especially if they're male, doing all kinds of extraordinary extravagant things to try to get the attention of the opposite sex. So you've sent us a couple of clips of what happens with the birds you've been studying. First of all, we're going to hear the sound of a male just singing.

Mimi - Well, you'll hear a short clip where the male sings a couple of repetitions of his song. And he knows how to sing it, but sometimes it's a little variable and he might also vary the timing, so there might be some pauses.

Chris - And we're going to contrast that with what happens when you introduce a female into the mix, so the male's aware that there's a female there.

Mimi - Yeah, so we think of this as a high intensity performance song. He sings faster, he sings more of the repeats. It's just a higher song rate.

Chris - But this is like, you know, doing extra flips on your skateboards, trying to get the girls interested.

Mimi - Definitely! The male is trying to get the female's attention and he's singing his best version of song. And even though we can't hear it, the female can hear subtle differences between when the male is practicing and when he's performing. And it turns out that the performance song is much more stereotyped from one trial to the next.

Chris - You mentioned earlier about how the brain wires itself up and then reaches this point at which it's optimally wired in order to start being able to acquire songs and then memorise them. Do we now understand though, which bits of the brain are doing that?

Mimi - There are two or three parts of the brain that are involved in this. Song motor areas that are producing the sound, auditory areas that are used for evaluating the performance of the song, and then there's a cortical basal ganglia circuit that we know is important for learning the song and for being able to change it from moment to moment, but also over the course of learning.

Chris - Are they the same bits of the brain that I'm physically using to talk to you?

Mimi - Yes, there are many similarities. Basal ganglia circuits are found in all vertebrates and they're important for motor learning and for motor performance in all vertebrates. And one thing that makes songbirds special is that, like humans, there are connections from the cortex to those motor neurons that then project to the parts of the body for producing the sound.

Chris - And does that mean if you know which bits of the brain are doing this, you can actually potentially manipulate it and thereby prove that that's how the birds are doing what they're doing?

Mimi - Yes. There've been a number of studies to manipulate either those motor areas that are responsible for producing the song or this cortical basal ganglia circuit that's important for learning and for changing the song.

Chris - And can you therefore physically change how a bird sings? If you were to go in and fiddle with those brain areas, would the song change?

Mimi - Yeah so for example, we can put in certain drugs into the brain to change the level of activity in that part of the brain. And if we do this in the cortical basal ganglia circuit and we activate it, so we cause it to fire more and to send signals at a higher rate, then we can drive changes in the song and cause the bird to change the performance of individual syllables, for example, altering the pitch. We can also change the sequence of the song. And most recently we've shown that we can cause birds to stutter so that they'll repeat certain elements of their song a small number of times before moving on to the next syllable.

Songbirds have been singing, and learning how to sing, for likely millions of years. But now there’s evidence that in recent years us noisy humans are disrupting the process. Sue Anne Zollinger is from Manchester Metropolitan University and she studies how birdsong is changing. She spoke with Chris Smith about the impacts that humans are having on birds, and on birdsong...

Sue Anne - Well, lots of noise that annoys us as humans is also what's interfering with birds being able to hear, and properly learn like traffic noise, airline noise, and other kinds of industrial noise pollution, that makes it harder for us to communicate also when we're exposed to it.

Chris - How do we know that's going on?

Sue Anne - We know birds do a lot of things differently in noisy places. So if you look at the songs of birds that live in noisy cities, their songs have started to diverge a little bit from what we hear in their traditional habitats, like quiet forests or grasslands. And those kinds of changes depend on the species. So lots of species around the world start to sing in slightly higher pitch in cities, and that's thought to help them avoid the loudest part of that low frequency rumble that you get from road traffic noise. Lots of birds, we know, sing louder, but they're not able to sing as much louder as they need to, to be able to really belt it out over the din of that traffic noise often. And sometimes they also change when they sing. So sometimes in really busy urban areas, birds start to sing earlier in the morning, or later at night to try to avoid those peaks of traffic that you get at rush hour.

Chris - So they're compensating, but it doesn't necessarily solve the problem, every time.

Sue Anne - That's right.

Chris - You've been doing some experiments on this, haven't you and you sent us some clips of this. So let's have a listen to these. The first one that you've got here is the gold standard. And perhaps you could begin by just telling us how you did the experiments and what this gold standard song that we're going to hear is.

Sue Anne - We wanted to look at how the noise would influence development. So during that process Mimi was just talking about where they have to go through this process of listening, learning, and imitating the song that they hear. And so we had half of our birds growing up in a quiet room and half of them in a room filled with traffic noise, like you would experience in the city. And we wanted all the birds to have the same opportunity. So this golden tutor that we're going to listen to is the song that all of the birds heard.

[TUTOR BIRD SONG]

Chris - So the first group of birds you mentioned, had a pristine environment as it were, they were exposed to that song we just heard, they had to learn it. And this is the result I presume, you're going to play for us now, of them learning that song.

Sue Anne - That's right this is the example of a juvenile from that quiet room. What I hope you can listen to in this song is that he doesn't sing exactly the same song, but he copies a lot of those syllables that have the same kind of rich harmonic structure you can hear in the tutor.

[GOOD LEARNER BIRD SONG]

Chris - And now we're going to delve into what happens when you expose them to motorway noise. This is the traffic group. What are we listening for this time?

Sue Anne - This guy, he doesn't copy any of those syllables. So it's a little hard for us to hear as humans, because we don't have the good ability to hear those fine differences. But what I want you to listen for is that none of the acoustic structures are the same. So it sounds a little more rough and click-like. It's kind of harmonically, not as nice.

[BAD LEARNER BIRD SONG]

Chris - So an example of a less good learner caused by exposure to noise pollution. How does that actually affect the birds downstream though, Sue Anne, what objective evidence have we got that it is?

Sue Anne - We know from some field studies that females in urban areas prefer the songs of males from quiet areas, so that if you give them a choice where they have an option to select one or the other, that they prefer the song like the traditional songs and not the ones that are shifted to adapt to traffic noise. So if males aren't able to sing good quality songs because of disruption of learning, by traffic noise, that they're going to have less success in attracting good quality females and defending good quality territories.

Chris - And presumably then, that means that that could unpick the beneficial effects of what natural selection is trying to do, to improve the quality of the species, you'll end up selecting poorer quality males.

Sue Anne - Yeah. It could also be, you know, that females also need to learn. So they go through this process, even if they don't end up singing the songs, of learning what songs are good. We don't know yet, but it can be that females' preferences, and their learning of what songs are good quality is also disrupted by noise. And so it might be that females in noisy areas aren't able to make good choices for good quality.

Chris - Are we being a bit shortsighted and just focusing only on sound in terms of mate selection here, are there other potential impacts on birds, of us making noise pollution? Because I know for instance, if you look at humans, if they live near a busy airport or a busy road, they have higher blood pressure because of stress. Is it true for birds that when they have to tolerate us, that it causes knock-on effects?

Sue Anne - Definitely. So that's something that I've been studying in my lab for the last 10 years or so. We know that birds in urban areas, or even just exposed to noise in a laboratory, that they have disrupted stress physiology, they age faster, and there are reductions in reproductive success. So how many successful offspring they can produce. On top of that, by disrupting non-song communication, like alarm call detection, that risks that they are more vulnerable to predation, for example, if you don't hear the warning that the predator is more likely to catch you.

Chris - I'm also thinking of one of our human behaviours, is to route aircraft, for example, over areas where people aren't. Now, birds are going to make a beeline, if that's the right phrase to use, for areas which are sparsely affected by humans. And so therefore, are we potentially taking and exporting our noise to them in other ways, which is going to prove equally disruptive.

Sue Anne - Yeah, that's right. We know that a lot of areas that are too noisy for humans, we plant up with really lovely habitats, looking for birds, trees that are going to protect the humans nearby from those loud noises. And so birds are kind of drawn to those. And we consider those almost like an ecological trap, that we attract in, animals, wildlife, birds, to these beautiful looking areas, but that this loud noise actually has very serious consequences on their fitness, their ability to thrive and procreate properly there.