Intelligent predator control – why shooting everything in sight isn’t the answer

For most people involved in conservation, predators are an ever present problem. A few years ago, I was at a lecture hosted by the GWCT, which explored the findings of research into predator control in the uplands. Over the course of eight years, a group of GWCT-backed researchers studied the effects of controlling predators on the prevalence of five species of ground-nesting birds.

The figures showed that the sustained control of foxes and corvids allowed lapwings, curlew and red grouse to breed three times more successfully than on ground where there was no control. And in the absence of predator control, the populations declined. Another GWCT piece of research in the late 1980s, the Salisbury Plain study, explored the impact of predation on the breeding success and population density of grey partridges on two plots of five square kilometres. The landmark study showed clearly that predator control increased the breeding success and subsequent population of grey partridges.

In a sense, it’s simple. The more predators there are, the worse ground-nesting birds will do, but the full picture is rather more complicated. There’s more to protecting waders and wild game than simply ‘whacking foxes’ and shooting every crow in sight. I have often seen badly thought-through attempts at predator control and inevitably this can lead to more problems. To make a real difference we must carry out intelligent predator control where consistency is king.

Before you get to consistency though, you need to work out what you’ve got on your ground.

Know your foe

Reconnaissance is everything. Dr Mike Swan of the GWCT says it always pays to know what you are up against, but he admits some species are trickier than others. “Traps can be used for detection and control at the same time — Larsens for invading crows are a good example. On the other hand, it is clearly bad to set snares for foxes when you don’t know what’s about. If there are no foxes you can only catch non-targets. Footprints and scat are worth looking out for.”

He notes that rats are a very real threat to ground-nesting birds too and that a thermal can be very useful. (Read our list of the best thermal imagers for hunting here).

Over the past few years, we have kept pretty accurate records of predator control that has been undertaken across my farm in Bedfordshire, where our modest grey partridge population is steadily rising. It shows when the peak times of control are for the main predator and pest species, and the way that these peaks dovetail with one another.

Ground-nesting birds such as grey partridges will thrive in a managed setting

Take grey squirrels, whose populations have been shown to increase in woodland where pheasant feeding takes place. Feeding of birds well into spring brings about an increased fecundity in the squirrels and the abundance of feed at feeders through the hungry gap increases the likelihood of them rearing all their young to maturity. The second litters are also more likely to succeed.

Targeting grey squirrels during the hungry gap, when the amount of natural food available to them is at its lowest, means the Fenn traps you are obliged to check daily are more likely to have yielded results, making your rounds more efficient and fruitful. On average we catch 20 squirrels a month, but in March of this year the number was 117.

Ramping up our squirrel trapping during this period, when the squirrels are desperate for food and more likely to come into feeders, has paid dividends. The population has significantly reduced, but if we are to continue game shooting, we have to continue squirrel control concurrently. If we create an abundance of something we have a responsibility to control it. It’s all about keeping the balance.

Early start

It is also worth noting that this same period is when you should be focusing on corvids. Mike Swan suggests “there’s very little point Larsen trapping after vulnerable birds have fledged, but it is good to start early, before eggs are laid”.

When it comes to foxes, it seems that year-round consistency is the key. Both at home on the farm and the estate I work on, they will take birds all year. The same applies to mink; the GWCT mink raft has been a game changer. Like corvids, trapping mink is more effective than shooting them.

The most effective method of fox control is lamping them at night or, if you have the tech, shooting them using night vision. Unless you’re a full-time keeper, though, getting out a few evenings a week can be difficult so maintaining consistent fox control is probably unlikely.

Lamping still has its place and night vision is expensive

This is where enlisting help can play a vital role in predator control. Many people will leap at the chance of having some land to go lamping across, but make sure they understand what you need. The foxes’ breeding season naturally coincides with that of their prey, and the demands of feeding the growing cubs intensifies the pressure on prey species such as ground-nesting birds.

Maintaining fox control during spring and summer is critical, but as the cereal crops grow towards full height and meadow grasses provide thick cover, finding foxes to shoot becomes more difficult. This is where well-placed and thought-through snaring can be deployed as an important predator-control method. The other benefit of snaring is that it is non-selective among the fox population. Lamping, for example, can often result in the shooting of very bold or rather naive foxes. The wary foxes are trickier, so catching these animals at breeding age through the use of snares is vital to maintain a balanced population.

The average crow eats about 11oz of food per day. For context, an average chicken’s egg weighs about 2.5oz. It is therefore easy to see how quickly a crow can cause significant damage to nesting bird breeding. Our corvid control peaks in April, which appears to be the best time to deploy traps. While territorial crows and magpies are seen as having the most devastating impact on nesting birds, the flock-living corvids such as rooks can be equally detrimental due to the numbers involved.

When setting up a cage trap for predators make sure you fully comply with the law

I have witnessed the destruction of an entire silage crop by a flock of rooks, causing damage worth thousands of pounds.

Corvid control is vital for so many reasons and has been shown to have a direct impact on the prevalence of songbirds. Some studies have shown as much as a 16% impact on hedgerow-nesting birds. The best time to catch corvids is the spring, when they can be trapped humanely as they search out food for their young. One difficulty is that as the population of corvids on our land decreases, so the incidences of birds venturing across from neighbours increases.

The removal of crows on one piece of land can invite forays from other territories, which can be as damaging as if you had simply left your own crows alone. The average territory size for a crow is about 10 acres, so this gives you a good idea of what your crow numbers should be — get rid of them all and you’ll create a vacuum.

To counteract this, we have found that deploying traps on the boundaries or sometimes in collaboration with the neighbours on adjoining land, the sphere of influence increases and overall predation seems to reduce.

With foxes of breeding age, snares can be useful in maintaining a balanced population

Boundaries

While Larsen traps are highly effective at controlling crows and magpies, they are unlikely to make a dent on large populations of rooks. The careful deployment of multi-catch cages therefore is a great tool for reducing flock corvids. It is important to note that much of the predator control undertaken in the UK falls under the general licence and that conditions must be met in order to be allowed to control certain species. It is critical you comply with the law.

Controlling predators can’t be done overnight, but long-term persistence over many years can help deliver the conservation goals, livestock and tree protection needed for a healthy landscape. Finally, always keep a tally — it lets you see what populations are doing. Records are crucially important, too, in case you mistakenly trap a species that you shouldn’t.