The conservationist's dilemma - 3

Written by: Martin Harper
Published: 20 Jun 2016
Topic: Science, policy and practice of the impact of predators on wild birds.

Martin Harper visited Insh Marshes, which lies on the floodplain of the River Spey and is a special site for breeding waders (Snipe, Curlews, Lapwings, Redshanks), rare plants (eg String Sedge) and invertebrates. He found it to be a magical place with the floodplain retaining many characteristics of a naturally-functioning system. He saw on site the impact of the wet winter of 2015 and that one of the tributaries had cut a new path, creating dynamic wet features alive with wildlife.

A study of Lapwings productivity was being undertaken at Insh Marshes as there's been a decline in recent years and previous research has been unable to identify the main cause. At the time of writing a dedicated researcher was monitoring the nests and the chicks. The initial results showed that many early nests were lost during the night with significant fox activity identified on the trail cameras and Badgers also present. This study led to consideration of whether Red Fox control might be required as the flood regime means it isn’t practical to install an anti-predator fence.

A study of Lapwings productivity was being undertaken at Insh Marshes as there's been a decline in recent years and previous research has been unable to identify the main cause. At the time of writing a dedicated researcher was monitoring the nests and the chicks. The initial results showed that many early nests were lost during the night with significant fox activity identified on the trail cameras and Badgers also present. This study led to consideration of whether Red Fox control might be required as the flood regime means it isn’t practical to install an anti-predator fence.

The RSPB's 2007 review of the evidence of the impacts of predation on wild birds concluded that generalist predators, such as foxes and corvids, can sometimes reduce the population levels of ground-nesting birds (such as waders, seabirds and gamebirds), and a more recent review confirmed these findings. By contrast, the evidence that breeding songbird numbers are limited by predation is weak. Rather, there is compelling evidence – some of it experimental – that changes in farming practices have led to the declines of many farmland songbirds, and emerging evidence that numbers of some woodland songbirds have declined due to long-term changes in woodland structure.

The RSPB's 2007 review of the evidence of the impacts of predation on wild birds concluded that generalist predators, such as foxes and corvids, can sometimes reduce the population levels of ground-nesting birds (such as waders, seabirds and gamebirds), and a more recent review confirmed these findings. By contrast, the evidence that breeding songbird numbers are limited by predation is weak. Rather, there is compelling evidence – some of it experimental – that changes in farming practices have led to the declines of many farmland songbirds, and emerging evidence that numbers of some woodland songbirds have declined due to long-term changes in woodland structure.

The RSPB's approach is to seek evidence of a problem, check whether there is a non-lethal solution, make sure that the killing of predators would be legal, effective and not harm their own conservation status. Only once the RSPB is satisfied of all these things does it make a decision. The tables below show the lethal vertebrate control undertaken on reserves. Some of the numbers are higher than in previous years as the dataset covers a 17-month due to a change in the annual reporting schedule.

It is worth remembering that non-lethal approaches, although not realistic in some circumstances, can be very effective. To illustrate this point a graph has been included to show how well anti-predator fences are performing. At sites with anti-predator fences, Lapwing productivity has been consistently above that necessary for population maintenance, even though at most sites only a proportion of the suitable habitat is protected by the fence (Fig. 1).

This is a fantastic result and a great return for the effort invested by the RSPB's ecologists and reserve teams.

Below are tables summarising the vertebrate control undertaken by RSPB and our contractors on reserves during the period 1 April 2014 to 31 August 2015. The recording period is longer than in previous years as we altered our annual reporting timetable. The extended period means that higher numbers of vertebrates were killed than in the previous 12 month reported period. Only reserves where control was undertaken during the year have been included. Vertebrate control commissioned by third parties as part of existing rights is not included here.

NB Feral means released birds outside their normal range.