The main driver behind the decline of our beloved meadow birds in many parts of Europe is insufficient breeding success as a result of high levels of predation. Fewer chicks fledged means fewer become breeding birds themselves, reducing population size over time. To reverse population declines of species like black-tailed godwit and lapwing this tide must be turned. We have just published the results of a study that trialled temporary electric predator exclusion fencing aimed at reducing predation to increase nest success. The study is published in Ecological Solutions and Evidence by Verhoeven et al.

The ‘where’ matters

Breeding success of meadow birds such as godwits and lapwings differs in nature reserves compared to outside nature reserves. Outside nature reserves, negative impacts of agricultural activities like grassland mowing are the main cause of the low breeding success these ground nesting birds experience.

Lapwing sitting on a nest (c) Ian Francis (rspb-images.com)

In nature reserves, where the negative impacts of agricultural activities are minimized, predation of eggs and chicks is the main reason for low productivity of nests. We combined data from two very similar projects both focussed on wader conservation. One was in England, an EU LIFE funded project to restore black-tailed godwit populations, and the other in The Netherlands.

Nest monitoring at both these projects identified red fox as the main predator of eggs especially and, along with other predators, foxes also predated chicks.

Exclude the fox

The use of electric predator exclusion fencing has become a commonly used tool on nature reserves to prevent predation by foxes and other mammal predators (see here). This is costly and not always possible to power or maintain, for example due to spring flooding. Their effectiveness and optimal application are also frequently questioned.

We aimed to halt predation by foxes and other medium sized mammals by using temporary ditch-side electrical fences that could be put up each year in the places most likely to contain ground nesting birds. We monitored the predator community before and after fencing, and found that foxes were successfully excluded from areas with functioning electrical fences.

The authors tested whether ditch fences, like the one above, could reduce wader predation (c) Tommy Pringle (RSPB)

Survivors

We also closely monitored godwit and lapwing nests in England and the Netherlands, in all years of the fencing trial nest survival was substantially higher within areas enclosed by ditch-side electric fences than outside.

The survival of chicks after leaving nests was also assessed for godwits in The Netherlands, and was also higher within the fenced area in both years. These higher survival rates likely result from a reduction in the total number of foxes hunting within the area. This effect is found despite some other predators still being able to access these areas, aerial predators like crows and birds of prey.

Our study shows that temporary electric fencing can have a positive effect on nest and chick survival, and so is a useful tool for increasing breeding wader populations.

Survivors on the move

Broods of chicks stayed inside the larger fenced area in The Netherlands (107 ha) but moved out of the smaller fenced area in England (67 ha). We therefore recommend fencing as large an area of high-quality habitats containing breeding waders as practical to: 

  1. protect a greater number of nests and especially chicks as they move after hatching
  2. minimize the area of high-quality breeding habitat left exposed to ground-predators outside the fence
  3. limit the effect of a potential increase in predation pressure outside the fence
  4. increase cost-effectiveness, since the cost of fencing material per meter decreases as fence length increases.

However, we caution against making a fenced area too large as for fencing to be functional and effective, it must be well-maintained along the entire length.

Black-tailed godwit and chicks on nest in Netherlands (c) Project Godwit

Fencing = not for the long term

Although our study clearly illustrates that temporary ditch-side electric fencing can improve wader productivity in lowland grasslands, electric fences are not part of a naturally balanced ecosystem. Electric fences should be a temporary measure to increase wader productivity and buy the time required to find more natural solutions that can be applied at the landscape scale.

Drivers of predator populations

Our results provide a glimpse into a more sustainable natural solution: the annual variability in nest survival showed the same trend inside and outside of fenced areas, with years of low or high survival inside fences mirrored outside fences. This indicates that in both countries, factors other than fox presence and agricultural activities also impact wader nest survival variably across years.

We suggest that factors regulating predator populations and predator behaviour are at least partly responsible for the observed annual variation in nest survival. Such factors could include annual variation in the abundance of voles or other prey species, or variation in the local abundance of different predator species, changes to predator behaviour, prey behaviour, and vegetation structure as a result of flooding.

We therefore believe that a better understanding of what drives predator pressure on ground-nesting birds is the required next step to find more sustainable natural solutions to manage predators at a landscape scale in areas where breeding waders are concentrated in discrete patches of suitable habitat.

For the full paper: Do ditch-side electric fences improve the breeding productivity of ground-nesting waders?

Acknowledgements

In The Netherlands we are grateful to many farmers, most of whom are organized in the Collectief Súdwestkust, and Staatsbosbeheer for funding. In England, the fencing and fieldwork was funded in 2015/16 by Natural England through the Action for Birds in England programme and from 2017-19 through an EU LIFE Nature Programme project (LIFE15 NAT/UK/00753) in partnership with the Wildfowl & Wetlands Trust, with financial support from the National Lottery Heritage Fund via the Back from the Brink Programme. Analysis was joint funded by the EU LIFE project and Vogelbescherming (BirdLife Netherlands).

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