I’ve noticed a worrying and increasingly frequent trend recently. Often, when there is a bad news story (and there are many of those) about a species that is in decline and struggling, there seems to be a concerted attempt to find another species to pin that decline on. The usual format is species X is in decline due to predation by species Y. This is commonly backed up by science that tells us that predation is causing this decline. I don’t for one minute doubt that predation is a contributing factor in species population dynamics, it was ever thus. But by blaming a predatory species we are subtly moving the liability from what is ultimately the primary cause of species decline and loss of biodiversity, and that factor is humans. Corvids predating ground-nesting birds, badgers predating ground-nesting birds, magpies predating small passerines, sparrowhawks predating songbirds, badgers predating hedgehogs, pine martens predating woodland birds, cormorants and goosander catching salmon, otters catching fish, stoats taking wader chicks, foxes – foxes get blamed for a lot of things – the list goes on. In each case, I don’t deny they have an impact. However, in each case it is possible to find anthropogenic reasons which have at least an equal and often greater impact.
But predators are increasing! Yes, several generalist predator species are increasing but, and this is a crucial but, why are they increasing? How have predators and prey lived in harmony for millennia but now, suddenly, the predators are increasing and wiping out their prey? Anyone who has a basic knowledge of population ecology will have seen the Canadian lynx and snowshoe hare population graph. The relationship between lynx and snowshoe hare is a classic example of predator-prey dynamics in nature. Lynx are the natural predators of snowshoe hares, and their populations are closely linked. When the population of snowshoe hares is high, the population of lynx increases as well, as there is more prey available. However, as the population of lynx increases, the population of snowshoe hares decreases due to predation, which then leads to a decline in the lynx population as well, as there is now less prey available. This cycle repeats itself over time, with the populations of both species rising and falling in response to each other. However, the lynx never completely wipes out the snowshoe hare population, the balance is always restored. That is how predator-prey relationships work when they aren’t affected by external factors.
Generalists vs Specialists
As human activities such as urbanisation and agriculture have fragmented natural habitats, some generalist species have been able to adapt to these new habitats and increase in numbers. However, it is important to note that this increase in generalist species is not necessarily a positive trend, as it can lead to a loss of biodiversity and ecosystem function. Generalist species may outcompete specialist species, leading to a homogenisation of ecosystems and a loss of unique ecological niches. Therefore, it is important to balance conservation efforts for both generalist and specialist species to maintain healthy and diverse ecosystems function.
Changes in Land Management
Many of the UK’s species declines have coincided with changes in farming and land management since the Second World War. The changes in farming practices since 1945 have led to increased productivity and efficiency, but also to environmental challenges such as soil degradation, water pollution and loss of biodiversity.
The biodiversity loss since the year of my birth, 1970, makes for depressing reading. Since the 1970s, the UK has lost more than half of its farmland bird population, including those of species such as the grey partridge, corn bunting and skylark. This is due to changes in farming practices, such as the use of pesticides and the loss of hedgerows, grasslands and other habitats. Skylarks have declined by around 60% in this period. Water vole populations have declined by over 90% since the 1970s, due to habitat loss and fragmentation, as well as predation by non-native species such as American mink. Note here that the predator involved in the water vole decline is non-native, a species that has been introduced into the ecosystem by humans and upset the natural balance. Many freshwater species in the UK, such as fish, amphibians and invertebrates, have declined significantly due to pollution, habitat loss and other factors. For example, the European eel population has declined by over 90% since the 1970s.
Many woodland species are also in decline and again predators such as jays, squirrels (usually grey but also red), pine martens, badgers (again), foxes and crows all take a fair amount of flak for their eating habits. But again, the majority of UK woodlands are in a poor state, often with denuded understories, lack of standing deadwood and very little new growth. The UK woodland bird indicator shows a declining trend in the population of woodland birds in the UK. The indicator is based on a set of 14 bird species that are associated with woodland habitats, such as the great spotted woodpecker, the nuthatch and the treecreeper. According to the indicator, the population of woodland birds in the UK declined by around 27% between 1970 and 2019. This decline is due to a range of factors, including habitat loss, fragmentation and degradation, as well as changes in land use and climate change.
The Blame Game
At this point I am sure some of you will be jumping up and down shouting at me to not blame the farmers and landowners, so I’ll be clear, I am not. Well, not entirely. Some of the most detrimental farming practices such as hedgerow removal, wetland drainage and intensification were driven by Government policy and subsidies. Other drivers such as the desire for cheap food and food security have caused over-use of pesticides and fertiliser, over-grazing and changes to the timing of sowing, harvesting and ploughing cycles, which again have been detrimental to wildlife. Supermarkets are pushing the green agenda and crowing (pun intended) about their reduction in plastic and packaging. However, at the same time they are forcing down food production prices for farmers, which increases the pressure on them to cut environmental corners in order to make a profit from all their hard work.
I am not blaming farmers and land managers alone; I am blaming humans as a whole. However, let’s take a look at some of the other suspects on the list.
Crows and Magpies
Crows are known to prey on a variety of animals, including small mammals, insects and birds. Crows are opportunistic predators and will take advantage of any available food source, including the eggs and chicks of ground-nesting birds such as lapwings, curlews and plovers. While they may occasionally take the eggs or young of ground-nesting birds, though, they are not considered a major factor in the decline of these species. However, in areas where crows are abundant and ground-nesting birds are scarce, crows may have a significant impact on the breeding success of these species. It is, however, important to note that crows are not the only predators of ground-nesting birds, and other factors such as habitat loss and fragmentation, climate change and human disturbance can also contribute to their decline. In some cases, crows may even help to control populations of other predators, which could benefit ground-nesting birds. Overall, the role of crows in the decline of ground-nesting birds is likely to be relatively minor compared to other factors.
Magpies are known to prey on a variety of animals, including small mammals, insects and birds, and they have been observed taking the eggs and young of some garden bird species. However, the impact of magpies on garden bird populations can vary depending on a range of factors such as habitat, prey availability and human activity. While magpies may pose a threat to some garden bird species, they should not be considered a major factor in the overall decline of these species. Habitat loss, fragmentation and degradation, as well as predation by other animals such as cats. squirrels and rats, are more significant factors in garden bird declines.
Hen harriers are known to feed on small mammals, birds and occasionally reptiles and amphibians. While they may occasionally take the eggs or young of ground-nesting birds, their impact on these species is generally considered to be minimal. In fact, some studies have suggested that hen harriers may actually benefit ground-nesting birds by controlling populations of other predators, such as foxes and crows, which can prey on the eggs and chicks of said birds. However, hen harriers are also known to prey on red grouse, especially in areas where red grouse numbers are artificially high such as managed grouse moors. Overall, though, while hen harriers may have some impact on ground-nesting birds, their role in the decline of these species is likely to be relatively minor compared to other factors such as habitat loss and fragmentation and climate change.
When I worked as a countryside ranger, one of the most frequent questions I used to get asked was “How do I get rid of sparrowhawks, they are taking all the little birds who use my bird feeders?” I even knew people who said they would stop feeding the birds so that the sparrowhawks couldn’t kill any, which I’d argue would be more detrimental to the garden bird populations than the occasional sparrowhawk kill. Again, predator-prey dynamics dictate that sparrowhawks and other raptors never kill all the birds in an ecosystem, so, as difficult as it is to watch a sparrowhawk catch and kill a bird on a bird feeder, it is a natural part of the population cycle. There are over 12 million domestic cats in the UK, with research estimating that they take between 100 and 270 million prey items a year, many of which will be garden birds, but also include rodents and reptiles. The UK breeding population of sparrowhawks is estimated at around 35,000 pairs, so the impact sparrowhawks make on garden bird populations is negligible in comparison.
Badgers are often blamed for the declines in ground-nesting birds as they have been seen on trail cameras taking eggs from nests. Badger numbers are declining (over 210,000 have been killed in the Government’s Badger Cull programme alone) so how can they be having a larger effect on ground-nesting birds now than they used to several decades ago? That premise doesn’t make ecological sense, unless the badgers have changed their foraging and eating habits. And then, if they have changed their eating habits, why is that? Could it be because there are less of their usual prey items around, such as earthworms? Studies show that earthworm numbers have declined by around 30% in the last 25 years due to pesticides, land drainage and inorganic fertiliser use.
And what about hedgehogs, another species the badger is blamed for its decline? Hedgehogs are now at a critical level in the UK and are vulnerable to extinction. Hedgehog populations in the UK have declined by around 50% since 2000 and by over 90% since the 1950s. This is due to habitat loss, fragmentation and the use of pesticides. Road kills alone account for approximately 100,000 deaths each year, which is a major factor rather than badgers binge eating them. Each time we investigate deeper, the root cause of the issues is anthropogenic. And while we are on the subject, hedgehogs eat the eggs of ground-nesting birds too, so if their numbers are declining, wouldn’t that mean there are less eggs being taken? You see, it’s much more complex than blaming predators. They call it a food web for a reason: it’s a tangled, intricate world out there.
Grey squirrels were introduced to the UK from North America in the late 19th and early 20th centuries. The first recorded release of grey squirrels in the UK was in 1876, when they were introduced to the grounds of Henbury Hall in Cheshire. Over the following decades, more grey squirrels were introduced to other parts of the UK, both intentionally and accidentally, and they gradually spread throughout the country. Today, grey squirrels are widespread across the UK and are considered an invasive species as they have had a negative impact on native red squirrel populations and can cause damage to trees and other vegetation. Grey squirrels are known to raid bird feeders and eat bird eggs and chicks, which can contribute to declines in garden bird populations. They may also compete with birds for food and nesting sites, and their presence can alter the structure and composition of woodland habitats, which may impact bird populations.
Additionally, grey squirrels are carriers of the squirrelpox virus, which is fatal to red squirrels, a native species in the UK. As grey squirrels have largely displaced red squirrels in many parts of the UK, this has led to a decline in red squirrel populations. Overall, while the role of grey squirrels in garden bird declines may not be as significant as other factors such as habitat loss and predation by other animals, they can still have an impact on bird populations, particularly in urban and suburban areas. For me, the main problem here is that grey squirrels are not a native part of the UK’s flora and fauna and as such don’t quite fit into the ecosystem in the same way a naturally occurring species with its own predators would. Of the species that do predate them, they themselves are also depleted and hence not capable of controlling population numbers as they would within a balanced ecosystem.
Pine martens are not known to play a significant role in the decline of woodland bird species. In fact, recent studies have suggested that pine martens may actually benefit some bird species by controlling populations of other predators, such as grey squirrels, which can prey on bird eggs and chicks. Pine martens are carnivorous mammals that primarily feed on small mammals, such as voles and mice, but they may also eat birds, eggs and insects. However, their impact on bird populations is generally considered to be minimal, and they are not considered a major threat to woodland bird species. Instead, habitat loss, fragmentation and degradation, are more commonly cited as factors contributing to declines in woodland bird populations.
Humans have played a significant role in biodiversity loss in the UK through activities such as habitat destruction, pollution, overfishing and the introduction of non-native species. Habitat destruction and fragmentation, primarily due to urbanisation, agriculture and forestry, have led to the loss of many native species and ecosystems. Pollution, including air, water and soil pollution, has also had a negative impact on biodiversity, affecting both terrestrial and aquatic ecosystems. Overfishing, particularly in marine ecosystems, has led to the depletion of fish stocks and the loss of marine biodiversity. Finally, the introduction of non-native species, either intentionally or accidentally, has led to the displacement of native species, the spread of diseases and changes to ecosystem dynamics. Climate change, which is largely driven by human activities, is also having a significant impact on biodiversity in the UK, affecting species distributions, phenology and ecosystem functioning. Overall, human activities have had a profound impact on biodiversity in the UK, and addressing these impacts will be crucial for conserving and restoring habitats and species populations.
Predator management, a euphemism for killing, is often touted as the solution, or at least part of the solution to the issue. So, if we kill all the predators, some of which, like badgers, are actually protected species in their own right, will all the declining prey species increase and recover? Their demise may slow a little, the inexorable decline on the population graph may even level off for a while, but ultimately, habitats are still disappearing. Does a landscape where we have a few waders, but no crows, gulls, badgers, foxes, stoats, weasels, squirrels or birds of prey really feel like a conservation victory and something to be proud of?
A farmer I know in Caithness oftens complains that it is ridiculous that he can’t cut his silage fields when he wants to because he has signed up to a curlew payment scheme that prevents him from cutting early. “But I have loads of curlews here, I don’t understand why conservationists are worried about them declining.” He doesn’t seem able to understand that the reason he has lots of curlews is directly linked to the fact he can’t cut as early in the season as he wants to. I spoke with another farmer who was telling me that his fields were full of waders. He said that when he cut his silage, oystercatchers, redshanks and curlews were all flying up but as soon as he’d finished, the crows were then in there taking the chicks and eggs. It was hard to work out how he didn’t realise that the act of cutting silage was destroying the nests and the crows were just feeding on the subsequent death and carnage he’d caused.
I watched helplessly as another farmer drove round the field margin spraying weedkiller on the thistles whilst causing several pairs of redshank and oystercatcher to go into a panic of alarm calls as their nests were either sprayed or destroyed. Do these practices seem more detrimental than a badger caught on trail camera taking eggs from a wader nest? I’ve seen the nests of ground-nesting birds trampled by livestock, but I don’t see a clamour for all the sheep and cattle to be culled. However, it is also important to remember that as with any profession, there are farmers who are good at their jobs and others than aren’t. Similarly, I know good ecologists and I know bad ecologists, there are some out there I wouldn’t trust with my favourite house plant never mind the management of a nature reserve.
Yet, while it is very easy to descend into anecdotal evidence, with someone quoting an example of a fox eating all the eggs in a curlew nest and me citing a farming practice where I’ve seen nests destroyed, that isn’t going to bring us any nearer to a workable solution to the problems.
For each species where a predator is being blamed for its decline, it would be easy to find a human cause that is more detrimental to that species than the predator’s impact. So, why do we feel the need to shift the blame elsewhere? In some quarters, it almost seems that blaming predators has become a lazy shorthand for a bigger environmental issue and is used by farmers, land managers and conservationists who should know better. So, the next time you hear someone blaming a predator for the impending demise of another species, stop for a second and ask yourself if there is an underlying anthropogenic cause that we would be better off addressing in the long term? I realise this is not easy for many reasons, but especially because owning the problem would mean taking a long, hard look in the mirror and admitting we are the most destructive species that has ever existed on earth.