The conservationist's dilemma: an update on the science, policy and practice of the impact of predators on wild birds (4)

Deciding to introduce any form of predator control (lethal or non-lethal) is something we never take lightly. It’s always based on evidence* and guided by our Council-agreed policy.

The RSPB’s approach to any type of predator control means that we first seek evidence of a problem, check whether there is a non-lethal solution and if so implement that. In many cases this does the job needed.

One such example is at the RSPB’s Otmoor nature reserve in Oxfordshire, currently celebrating its twentieth anniversary, where our team of staff and volunteers have created a wonderful wetland giving homes to waders such as lapwing, redshank and snipe. Our management has also aided the return of bittern, marsh harrier and crane. Otmoor is providing the missing link to the wetlands in the Fens in the east and those in the Somerset Levels to the west.

RSPB Otmoor by Eleanor Bentnall (rspb-images.com)

Those of you that have visited the site will not have failed to have noticed the electric fence around the field we call ‘Big Otmoor’ (shown below).  This is designed to exclude mammalian predators and has been instrumental in driving up the productivity of lapwings. 

It may seem incongruous to see this structure in the middle of a nature reserve but this level of management is our response to the fragmented nature of our countryside and our motivation to re-engineer wildlife back into the landscape. As you can see from the graph below, the fence, which was installed in 2010, works and has helped deliver more wader chicks for visitors to see and to join the thriving population.

What's more, anti-predator fences are performing well across our reserve network.  We now have fences at 28 reserves protecting breeding waders over 874 ha. At sites with anti-predator fences, lapwing productivity has been consistently above that necessary for population maintenance (0.6 chicks fledged per pair), even though at most sites only a proportion of the suitable habitat is protected by the fence.  The graph below shows mean Lapwing productivity at RSPB reserves with anti-predator fencing, at which productivity has been regularly monitored. Bars show + one standard error. The figures above the bars show the number of reserves with anti-predator fencing, at which productivity was monitored.

But non-lethal methods, whilst always our preferred way of doing things, are not always practical. As I have written previously, lethal vertebrate control on RSPB reserves is only considered where the following four criteria are met:

• That the seriousness of the problem has been established;
• That non-lethal measures have been assessed and found not to be practicable;
• That killing is an effective way of addressing the problem;
• That killing will not have an adverse impact on the conservation status of the target or other non-target species.

If we can satisfy ourselves of all these things then we can be sure to make the right decision.

* Using results of previously published studies, we have completed a review of the impact of predation on birds.  This will be published soon and its results are consistent with those of our 2007 review: despite high and increasing densities of predators, we found little support that predation limits populations of pigeons, woodpeckers and songbirds, whereas evidence suggests that ground-nesting seabirds, waders and gamebirds can be limited by predation. 

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Vertebrates controlled on RSPB nature reserves 2015-16

As in previous years (see here, here and here), I have included two tables below which show the lethal vertebrate control undertaken (for both conservation and other reasons) on our reserves, which now number 210 sites covering more than 150,000 hectares across the UK, in the period 2015-16.  Some of the numbers are lower than in the previous year as 2014/15 was a 17-month period due to the change in reporting date.

a) control for conservation reasons

b) control for other reasons