Common Cuckoos are an intercontinental migrant that join a throng of other European birds making their biannual journey to and from Africa. Hearing the first spring cuckoo call is always emotional. It signals renewed optimism for the oncoming warmth of summer, the release of winter’s grip and a new season of plenty. It’s no surprise that hearing songbirds is good for our health. It harks back to our ancestral dependence on what they do for us. Faced with massive decline in the population of Common Cuckoos though, do we need to ask the question: why are cuckoos important? Need all of us care if they go extinct? The answers are a resounding yes. To persuade each other why, however, will take a new style of lateral thinking about animals.
This is the story I cover for the first time, in my book: Wildlife in the Balance. Here I’ll cover some of the principals as they relate to why the Common Cuckoo is important.
The impact of cuckoos: magnitude, scale and intensity
A pragmatic view of why animals matter means looking at the effect they have on our precious landscapes’ ecology. I call this ‘animal impactWhat is Animal Impact? Without wildlife, Earth would not be habitable for humans, because it's animals that stabilise ecosystems. It’s a fundamental law of nature that animals (and humans) exist because we are the most likely lifeforms to minimise environmental chaos. Animal impact, therefore, is a measure of how much all wildlife is collectively responsible for creating a habitable Earth. The More.’ It means we look at the risk of losing cuckoos by figuring out how much good impact they are having.
After all, this is a species that has existed for millions of years. Unless there was benefit to their existence they would have died out long ago.
This is not always an easy thing do, since so much wildlife has disappeared already. When we lose animals, we lose the ability to read, understand and interpret nature’s relevance to our lives. It’s one of the reasons why modern scientists argue about the benefit of ‘rewilding.’ Unbeknown to many we are studying broken and fractured systems in a state of disrepair and / or ongoing repair. It’s – unsurprisingly – become confusing.
The question therefore is, how do we deduce the importance of wildlife to humanity, when the evidence is now so threadbare? For that we need to take a look the magnitude, scale and intensity of their connection to our landscape and its ecosystems. That’s to say, using exactly the same method we trust to assess the negative impact of human development on the environment and turning it on its head.
#1 the magnitude of cuckoo importance
Cuckoos are a lot more abundant than we might think.
There are thought to be about 18 thousand Pairs of Common Cuckoo in the UK in 2016, down by 34% since 1995. We monitor cuckoo numbers using ‘pairs’ because we can more easily count singing males. Females are shyer and more secretive.
Only focusing on pairs, we can under-appreciate their real significance to ecosystems. We have to begin thinking differently about cuckoos if we want to change people’s minds about their importance.
Cuckoos have a familiar strategy that increases their impact. They use other birds to raise their young and lay 10-20 eggs each season. The British Trust for Ornithology (BTO) even says as many as 1-25 broods.
The benefit of an impact-assessment-style approach to determining the importance of cuckoos is that we don’t need to know exact figures to understand the scale of their impact.
Let’s assume an equal number of males and females produce, on average, fifteen chicks per pair. Each chick has an impact on the UK landscape’s ecology. That’s 15 chicks for every female, plus 18,000 males, plus an adjustment for the 34% decline. This means the seasonal population could have been in excess of 460,000 birds last century!
males | 18,000
females | 18,000
chicks (females x 15) | 270,000
minus 34% decline | 463,636#2 the scale of cuckoo importance
Another way to look at their impact is by the ‘scale’ at which they work for us. That’s to say, what area are they covering. Fortunately we have the BTO’s volunteer surveys again to thank for these data.
Cuckoos occupy about 80% of the UK. Mid last-century this was an area of 2,705, 10x10km squares. That means an average of one cuckoo for every 0.58 km2, about the size of a nine hole golf course. In reality it varies from bird-to-bird, with one study finding 85% of occupied habitat was between 1 – 17 km2.
Scale is also in terms of time. Humans only live, on average, about 80 years. The lifespan of cuckoos as a species is tens of millions of years. Their impact isn’t just seasonal, it’s a legacy of at least the last few thousand, if not hundreds of thousands of years.
area occupied (10x10km squares) | 2,483
minus 8.2% area decline since 1968 | 2,705
average UK cuckoos per km2 | 1.71#3 the intensity of cuckoo importance
Now we know how many cuckoos there are and over what area, we can look at the intensity of their impact.
This is where it gets tricky. Moskat et al (2019) is one of the few studies that looks at the concentration of cuckoo behaviour in the landscape. The scientists remark that ‘in patchy landscapes, home range estimation is technically not straightforward, because unused intervening areas may [be] beyond the biologically meaningful usage area.’ As I mentioned earlier, it becomes harder to deduce patterns of behaviour, as the landscape becomes increasingly, ecologically fragmented.
Remove cuckoos and what similarly important creatures can ever replace them? Nothing. Only more cuckoos can replace the cuckoos we have lost.
Despite this, as long as core habitat remains within reasonable flight distance, cuckoos can respond by moving between the most important locations. Humans pride ourselves on ‘managing’ the environment but we don’t really. Our interference tends to do more damage than good. We don’t have the right diversity skills or the abundance.
The mobility of a cuckoo is its superpower. This is, after all, a bird that can fly 26,000 km in search of its food. Up to a point it has little difficulty harvesting a living in a patchy landscape.
Cuckoos fastidiously collect, consume and recycle caterpillars, grasshoppers and other insects from among the branches, cracks and crevices of woodland.
In addition to a voracious appetite, cuckoos impart their impact on other species. For every cuckoo chick there are two other birds out feeding on the female cuckoo’s behalf. This creates a structural impact far greater than the birds themselves. To understand this we need to think laterally. There are examples of this everywhere in nature if we know where to look.
How can a handful of cuckoos make so much difference?
Because of their effect on the animals around them, cuckoos don’t need to be covering the whole landscape to have a profound effect.
The following graphic for wolves and beavers in the US illustrate how relatively few animals can form layers of structure that fit together like jigsaw pieces. One cuckoo putting top-down pressure onto reed warblers is exerting a significant influence. Similarly, birds like Hen Harriers and Goshawks exert top-down pressure on the cuckoos.
Even though cuckoos only impact small areas, we’ve already shown how they do this at a whole-of-landscape scale. They affect more than 80% of the UK. They’ve also been doing this for longer than any human or scientist can properly imagine. They and their brood-nest minions have been intensively harvesting insects every season for millions of years. They’ve been doing this successfully alongside thousands of other species, including humans.
In that system, everyone has been able to survive until today.
The positive impact of a few cuckoos
Cuckoos can keep insect populations in check because they have evolved to systematically select and consume creatures that would otherwise negatively impact food for mammals like us.
Long ago wild birds helped create the soil nutrients that allowed farming to be as productive as it has been for the last fifty years. We are still drawing off that legacy while almost literally killing the golden goose.
‘The absence of birds has direct consequence for human food production which is inevitably linked to carbon capture and climate, since the two are inextricably connected.’
– Using species’ potential range as an indicator of conservation importance
Each season of consumption suppresses surplus insect populations but this places greater (not less) pressure on vegetation. Cuckoos function(Of an ecosystem). A subset of ecosystem processes and structures, where the ecosystem does something that provides an ecosystem service of value to people. More in the same way as tiger sharks enrich seagrass by predating dugongs and spiders enrich grassland by predating insects. Predators don’t collapse ecosystems, they hold them together.
Over millennia cuckoos have been at the heart of building deep soil and so, they have fed thousands of generations – and that continues today.
We vastly underestimate the impact that only a few animals have on ecosystem structure. Ecosystems are pyramidal and regulated top-down – but not like you may think. They are top-down regulated throughout. Imagine taking any floor out from the Shard tower in London. It immediately becomes less stable.
Ecosystems, like buildings, are worth far more than the sum of their parts. Cuckoos are part of a structure that stabilises because of its connection to other animals around. Put another way. Ecosystems only function when they are full of all the right abundance and proportions of animals and birds. And cuckoos, due to the magnitude, scale and intensity of their endeavours, are a significant component.
Cuckoos transfer(of nutrients) the thing that sets animals apart from plants, is that they can move. Some of the biggest migrations on Earth every day, are the movement of insects like caterpillars, from the stem of a plant to a leaf and back, before turning into butterflies and transferring the energy elsewhere. Large-scale migration of grazing animals and migratory songbirds moves More and concentrate nutrientsEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More so that other birds and animals can congregate and amplifyAmplification (of nutrients and energy). Animals consume plants and other animals and in doing so, reintroduce important energy-containing nutrients back into the environment, at even higher concentrations and in patches. Amplification of energy is driven by migration and happens at every scale, from insects moving daily in and out of your vegetable patch, to African wildebeest herds and the seasonal More the seasonal effect. They are moderating the polluting influence of plant life by promoting diversity and ensuring carbon, nitrogen and other base elements for life, end up where they are useful, instead of where they are not: polluting our rivers, sky and ocean.
Migratory superpowers
Cuckoos’ migratory abilities, fastidious predation and parasitic breeding rituals mean they moderate energy more efficiently than anything humans can ever perfectly understand or reliably recreate.
They might do this at a relatively small scale from day to day but it’s at such magnitude, scale and intensity over time, as to clearly have enormous cumulative benefit – especially over thousands of years.
It’s also over vast distances. Cuckoos follow the sun to the places where there is so much risk of surplus energy in the ecosystem (in the form of food) that they migrate vast distances across whole continents.
‘Caterpillars are most common in places that are sunny and wet and so, in summer, there are plenty in the Khurkh valley, in the south-east of the Khentii mountain range. As the weather changes they go to India for monsoon season, and then, as the wind changes, to east Africa.’
Onun the cuckoo migrates 26,000 km (from The Guardian)
In northern Europe the first cuckoo call of spring would once have signified the arrival of billions of birds from Africa. The pendulum would swing each year to ensure the bounty of spring was maintained. Over millennia cuckoos have been at the heart of building deep soil and so, they have fed thousands of generations – and that continues today.
Science looks at how cuckoos are important … our hearts know why
For the last few decades we’ve been observing and measuring the decline of birds like the cuckoo without realising the true gravity of what’s been lost. Without bothering to ask (or answer the question): why are cuckoos important?
Reams of ecological studies are the same. The results are profound. We just haven’t learnt to interpret them properly yet, though we’re finding that hearing birds sing is good for our mental health. People are even happier living where there are more birds. Why is that?
Our ancestors were directly dependent on cuckoos for survival. Like the ancestors of people on Nauru today, a single bird can not only signify, but create food security. But these inter-cultural relationships take thousands of years to evolve. Science can only study what happens today or in the very recent past. Scientists are also looking at complex multi-generational systems reduced to simple, linear equations, against a backdrop of disintegration.
Proof is a panacea because ecosystems are too complex for science to ever understand completely. The only clues we have are in studying wildlife. A sophisticated scientific understanding of ecology though, is increasingly beyond our species’ reach because its wildlife components are being driven to extinction:
“It would be like if you were a particle physicist and you had to get up every morning worrying that the Higg’s particle went extinct”, John Harte, Berkeley University.
Like all animals, humans would have died out if they destroyed ecosystems in the past. We are the direct descendants of people who had evolved to cooperatively inhabit landscapes alongside cuckoos. We were part of a complex structure that transferred, concentrated and amplified energy into patches big enough to feed ourselves.
Science can give us glimpses into this value but only our hearts and minds can embrace the truth, that animals are humanity’s best hope.
Nature is in a dance and not a fight
By allowing nature to decline around us, we threaten our survival. Today, we are more dependent than ever on restoring ecosystems. That can never be done without also restoring animal life to past glory.
Our relationship with cuckoos is enduring and we regard them as harbingers of romance, bounty and nourishment They appear commonly in music, stories of folklore … even clocks.
The cuckoo is a fine bird he sings as he flies,
He brings us good tidings and tells us no lies.
He sucks the sweet flowers to make his voice clear,
And the more he cries cuckoo, the summer is nigh.
Purslow, Frank, ed. (1969). The Wanton Seed. London, UK: EFDSS Publications.
Today we’re inclined to think negatively about animals. Watch any nature documentary and you will see depictions of fighting and conflict. Real ecosystems are poised around balance and cooperation. A ‘dance and not a fight’, as I explain in Wildlife in the Balance.
We jump to calling small numbers of animals ‘pests.’ Like the way we unnecessarily persecute one or two birds of prey on grouse moors. Yet we find it hard to accept that equally small numbers of animals, in actual fact, have a significant positive impact.
Here I’ve looked at the Common Cuckoo. But these principles can apply to any animal at any scale. All wildlife is important because it led to the survival and success that humanity enjoys today. That’s why our future depends on a change in human values. One where we place the diversity and abundance of wildlife above everything else.
Remove cuckoos and what similarly important creatures can ever replace them? Nothing. Only more cuckoos can replace the cuckoos we have lost. That is why we cannot afford to lose them. It’s why cuckoos are important.
Spotlight
The BTO Cuckoo Tracking Project
Since 2011 we’ve been satellite-tracking Cuckoos to find out why they are declining. We’ve learned lots of vital information which could help us to understand our Cuckoos, such as how the different routes taken are linked to declines, and some of the pressures they face whilst on migration — but there is still more to discover.
