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

Today, I am speaking that the National Gamekeeper's Organisation AGM.

I was pleased to be invited and it promises to be an interesting meeting.  I expect a bit of reciprocal challenge and, hopefully, a shared desire for collaboration to help wildlife.

As part of my talk, I shall explain the RSPB's understanding of the impact that predators have on wild birds and our response.  I have previously written about how the RSPB uses the wildlife licensing system to support nature conservation (see here).  What follows is a bit of an update.

First a bit of context...

The NGO's AGM coincides with the breeding season and the RSPB is, of course, passionate about increasing the population of threatened species particularly on our 215 reserves across 151,197ha of land.  Dedicated work by a large team of staff and volunteers goes into creating just the right habitat to support priority birds (alongside the other 15,000 species that we are lucky enough to be responsible for on our estate).   As well as getting the habitat structure and the food supply right, we also have to ensure the birds are productive, raising a good number of chicks.

The great conservationist's dilemma comes about when one species (usually a predator) threatens the population of another.  The big question that we have to address, particularly on our own land, is what do we then do about it?

We have invested considerable research into the role of predators. This has included a review of the evidence of the impacts of predation on wild birds which concluded that...

...generalist ground predators,such as foxes, can sometimes reduce the population levels of their prey, and that this is a growing worry if we are to conserve populations of threatened ground-nesting birds, for example lapwings

...the evidence to implicate predators such as sparrowhawks in the declines of songbirds is very weak. 

A more recent (as yet unpublished) review confirms these findings. 

We have also done considerable work on the impacts of predation on breeding productivity of lapwings on lowland wet grasslands.  The research on lapwings has shown that, at the majority of sites studied, foxes are by far the most important predator of their nests. We have subsequently developed and installed predator-exclusion fences at suitable sites to help protect nesting waders against foxes (and also badgers at some sites). We now have predator-exclusion fences at 14 lowland wet grassland reserves.

Waders at Ham Wall, RSPB nature reserve (David Kjaer, rspb-images.com) 

Estimates suggest that lapwings need to fledge between about 0.6 and 0.8 young per pair to maintain a stable population. In 2013, at our reserves with predator-exclusion fences (such as Rainham Marshes), mean lapwing productivity was 1.05 chicks per pair.   Working with neighbouring land managers to restore habitats at a landscape-scale, we hope that the productive waders from our reserves will help to repopulate the surrounding countryside.

However, occasionally foxes get inside our fences and at some sites ground-nesting birds are too widespread for fences to be effective.  In these circumstances we have to use lethal control.  These decisions are never taken lightly and are guided by our Council approved policy.

As I have written previously, 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.

Below, I summarise numbers of vertebrates killed on RSPB reserves by us and our contractors during 2012/13. I have not included vertebrate control commissioned by third parties as part of existing rights.

As these tables show, there are four main situations where the above criteria are met. These are to:

• Increase breeding productivity of ground-nesting birds (mainly waders), principally by controlling foxes;
• Reduce numbers of deer where they are having a detrimental impact on the vegetation, especially by overgrazing the ground flora in woodlands and preventing tree regeneration.  Often deer management is undertaken to prevent damage or aid recovery of nationally important wildlife sites;
• Protect nesting seabirds;
• Benefit water voles by killing non-native mink.

We continue to wrestle with the conservationists dilemma, but are guided by the needs of threatened species, science and our policy.

I look forward to hearing, amongst other things, the response from the gamekeepers to our approach.  Tomorrow, I shall let you know how it went.