The Silent Skies: What Happens When Predator Control Stops in the UK Uplands?

Rob Beeson
May 8
7 min read

Birds like Golden Plover, Snipe, Curlew, Lapwing, Red Grouse, Black Grouse, and Grey Partridge all call the UK uplands their home, raising their young on the ground.

But these birds are facing significant challenges. Across Europe, bird populations have been declining. While factors like intensive agriculture and changes in land use are often blamed, there's a growing concern that something else might be playing a major role: an increase in generalist predators.

A fascinating and crucial study conducted in North Northumberland shines a stark light on this issue. Researchers revisited an area ten years after a predator removal experiment ended to see what had changed. The results are dramatic and offer vital insights into the complex world of upland conservation.

This blog post examines the findings from that study. We look at why predator numbers are high in the UK, what the original experiment showed, what happened when predator control stopped, and what the findings suggest for the future of these precious bird populations.

Why Are Predator Numbers So High in the UK?

Generalist predators - animals that eat a variety of prey - are on the rise in the UK. Species like the Carrion Crow and Red Fox are at densities that are either the highest or among the highest in Europe. But why is this happening?

The sources point to several contributing factors:

A Transformed Landscape: The UK landscape has been heavily shaped by intensive agriculture and the planting of non-native woodlands. These areas can provide more food availability for animals like corvids (crows) and offer refuge and breeding sites for predators.
The Missing Apex Predators: Crucially, the UK has lost most of its large apex predators, like Wolves and Eurasian Lynx. Golden Eagle and Goshawk numbers also dropped dramatically. Apex predators can help control numbers of smaller predators (mesopredators) and scavengers, either by directly killing them or by instilling fear that limits their activity. Their absence may contribute to the high numbers of mesopredators we see today.

Adding to this picture, national surveys show significant increases in other predators too. Since 1995, Breeding Bird Surveys (BBS) recorded an 89% increase in Buzzards, a 33% increase in Ravens, and a 17% increase in Carrion Crows. Indices from gamekeepers killing predators also suggest large increases in Red Fox (+180%) and Stoat (+50%) between 1966 and 2016. Badger numbers in England and Wales may have more than doubled since the 1980s.

This combination of factors has created an environment where generalist predators can thrive, potentially putting pressure on vulnerable prey like ground-nesting birds.

A Glimpse Back: The Original Experiment (2000-2008)

Recognizing the potential impact of predators, a crucial experiment was conducted between 2000 and 2008 near Otterburn in North Northumberland. The goal was to test the effect of legally removing generalist predators on ground-nesting birds.

Here’s how it worked:

The study involved four experimental plots in areas of moorland habitat.
On some plots, gamekeepers were employed to carry out legal predator control.
Predators targeted included Red Fox, Carrion Crow, Stoat, and Weasel.
During the experiment, the abundance of Red Foxes was reduced by an estimated 43%, and Carrion Crows by 78% in the areas where control took place.
Critically, habitat composition and management were kept similar between the areas with and without predator control.

The results of this initial experiment were striking. Where predators were controlled, ground-nesting birds saw a dramatic improvement. Breeding success for species like Lapwing, Golden Plover, Curlew, Red Grouse, and Meadow Pipit improved three-fold.

This led to subsequent increases in the breeding numbers of these birds in the areas where predators were managed, compared to declines in areas without control. This experiment, along with another at Salisbury Plain focusing on Grey Partridge, helped solidify the understanding that predation can indeed limit ground-nesting bird populations.

What Happened After Predator Control Stopped? (The 10-Year Follow-up)

The predator removal experiment finished in 2008, and predator control ceased on the plots. Fast forward ten years to 2018 and 2019, and researchers returned to the same experimental plots to see what had happened. They resurveyed the numbers of the same ground-nesting birds and predators that were monitored during the original experiment.

The changes observed were, in the words of the researchers, "dramatic".

Predators Bounced Back

Unsurprisingly, the predators that had been controlled during the experiment showed significant increases since control stopped.

Carrion Crow abundance increased by 78% compared to the experimental period.
The Red Fox index (based on scat counts) increased by a staggering 127%.

These predators had recovered to pre-management levels. The study suggests that the relatively small size of the experimental plots, surrounded by large areas where predators were not managed, allowed for rapid immigration back into the study sites once control stopped.

Protected avian predators, Buzzards and Ravens, also showed increases, which were consistent with wider UK trends for these species. Buzzard sightings increased by 48% and Raven sightings by 110%, though these increases were not statistically significant within the study plots themselves.

A Stark Picture for Ground-Nesting Birds

As predator numbers rose, the picture for the ground-nesting birds deteriorated significantly. The rapid declines observed were strongly associated with the recovery of these predator populations:

Black Grouse: This species suffered local extinction on the study plots between the end of the experiment and the resurvey. The source notes that the Black Grouse population on the wider Otterburn Training Area crashed from a high of 69 displaying males in 2003 to zero by 2014. While study habitat measures didn't show significant change, the increase of Goshawks in the nearby Kielder Forest is mentioned as a potential factor spatially and temporally linked to this decline, alongside potential contributions from Red Foxes and Carrion Crows.
Grey Partridge: This bird also became locally extinct on the study plots.
Golden Plover: Abundance decreased significantly by 81%.
Snipe: Abundance decreased significantly by 76%.
Red Grouse: Abundance decreased significantly by 74%.
Curlew: Abundance decreased significantly by 24%.
Lapwing: Abundance decreased by 58%, though this decline was not statistically significant in this study, it mirrors wider UK trends.

These are rapid and severe declines. The local extinctions of Black Grouse and Grey Partridge are particularly alarming.

Was Habitat the Problem?

Sometimes, bird declines are linked to changes in their habitat. The researchers anticipated this and monitored habitat composition and structure throughout the original experiment and during the resurvey.

Their findings offer crucial context:

Measures of dominant vegetation, such as Heather and Purple Moor Grass, and Heather height showed no significant difference between the experimental period (2002-2008) and the resurvey in 2019.
While other vegetation (like rushes) was found to be taller in the resurvey period, this could simply be due to seasonal or annual growing conditions.
Most of the study area was within UK government agri-environment schemes both during and after the experiment, which helped to restrict habitat changes.
Specifically for Black Grouse at Otterburn, the study notes that measures of habitat extent and quality had not changed during the decade in which the population crashed.

The fact that habitat measures remained largely stable reinforces the study's conclusion that the dramatic changes in bird numbers were primarily associated with the changes in predator abundance following the cessation of control.

Linking the Dots: Predator Recovery and Bird Declines

The message from this study is clear: the rapid recovery of generalist predator populations following the end of predator control was strongly associated with steep declines, and even local extinctions, of several ground-nesting bird species in the UK uplands.

These declines aren't isolated incidents. The study notes that the patterns of decline seen in their plots mirror broader trends among the same species across the UK, as recorded by national surveys like the Breeding Bird Survey. This suggests that similar processes - potentially including reduced predator management - might be occurring more widely in the uplands.

Predation by species like crows and Red Foxes is increasingly recognized as a factor that can limit the population sizes of gamebirds and waders by reducing their breeding success. Reviews of multiple studies have shown that experimental predator removal often leads to increases in bird populations. This resurvey in North Northumberland provides compelling evidence of the reverse effect - severe declines when predator control stops and predators recover.

What Can Be Done? Exploring Solutions

The findings of this study, and others like it, highlight a significant challenge for conservation: how to protect vulnerable ground-nesting birds in landscapes where generalist predators are abundant. The debate on the best approach is ongoing:

Lethal Predator Control: The study acknowledges that lethal control, particularly as part of traditional grouse moor management, has been shown to benefit ground-nesting birds in experimental settings. It is considered an essential component of conservation management in contexts of intensive gamebird management. However, lethal control is costly, needs to be long-term, and can be ethically contentious for many. Achieving effective levels of control might be impractical outside of intensive shooting areas.

Landscape Reconfiguration: Altering the landscape to make it less predator-friendly. This could involve removing non-native forests, which predators tend to favour but are often avoided by some waders and gamebirds.

Apex Predator Reintroduction: Given the historical loss of large carnivores from the UK, reintroducing species like Eurasian Lynx or Wolves is being considered. These animals could potentially help manage mesopredator populations. Some raptor reintroduction programs, like that for the White-tailed Eagle, have already been successful. Successful establishment of apex predators could benefit prey species and biodiversity more broadly.

Moving Forward

The rapid declines and local extinctions of ground-nesting birds documented in this study, strongly linked to the recovery of predator populations after control ceased, paint a concerning picture. These findings reinforce the results of the original experiment and align with wider UK trends.

Protecting these vulnerable species requires a multi-faceted approach. While lethal predator control has demonstrated benefits for ground-nesting birds, it's crucial to explore and trial other options too.

Landscape-scale habitat improvements and the potential reintroduction of apex predators could all be assessed for their effectiveness in benefiting prey species of conservation concern.

The future of the UK's iconic ground-nesting birds depends on finding effective, long-term solutions that can help them thrive in a landscape shared with abundant generalist predators.