Sunday, 24 July 2016

Another silent spring?

As spring passes to summer, we begin to gather data from nature reserves as to how birds have fared during the breeding season and to assess how conservation work for key species is progressing.  On a reserve that has ground nesting birds, such as waders, gulls or terns, an assessment can often be made very quickly and at an early stage, before the final figures are collated.  A productive site has a characteristic sound and feel: the noise of birds interacting with each other or defending their nests or young.  Lapwing or Redshank quickly rise to scold and chase passing crows.  ‘Kleep kleep-ing’ Avocets tell you that they have something left to fight for.  Usually the initial impression gained from a quick eye-ball of the habitat and a listen to the action tells all.

However, the incoming data will not be good on all sites.  There may be few chicks surviving, with overall productivity being low.  In fact, this is a widespread issue.  A study of the breeding success of key species from the Waddensea region of The Netherlands/Germany showed that 18 out of 29 were in decline, with poor breeding success being the important driver of decline. Three species, Avocet, Arctic Tern and Oystercatcher, had such poor breeding success that they were rarely able to reproduce themselves and local populations were in deep trouble.

When trying to determine the cause of low numbers of birds or poor productivity, two or three key issues are likely to hold the answer.  Poor weather in varying forms can cause problems.  In cold, wet conditions chicks will take longer to fledge or die of starvation or cold.  By contrast, dry conditions may also make food hard to find. Mitigating the effects of poor weather is often closely linked to habitat quality; a crucial factor that is well within the control of the land manager.  Wet grasslands in particular are frequently in poor condition; the sward is either too long or overgrazed, or the site often too dry.  Water control structures, if not maintained, can be leaky and in a poor state of repair.  Such problems are usually obvious to the trained eye.   Finally, and often the key issue when everything else looks to be okay, is the problem of predation.  This is the issue that is most often ignored as it asks some difficult questions for the conservationist.

For me, a trip to a range of French nature reserves a few years back was particularly illuminating.  Arriving one evening prior to an arranged reserve visit the following day, we wandered out to discover and enjoy a gloriously large, noisy, smelly, productive colony of Sandwich Terns and Mediterranean Gulls.  Next day, at the nature reserve, just a few Avocets loafed silently on a deserted island.  Apparently, when acquired, the reserve had thriving Avocet and Stilt colonies, but gradually the local foxes targeted the reserve and the birds moved on.  Reserve managers argued about controlling the foxes and finally agreed.  But just two foxes had been killed that year.  And what of the adjacent productive site?  It was owned and controlled by hunters who routinely undertake control of foxes.  An uncomfortable truth is revealed. Top reserves often seem to have plenty of staff asking for your membership or serving you coffee but not so many happy to understand and tackle the difficult issues of predation or habitat management.

Nature reserves surely have an obligation to deliver good breeding success for the key associated species. Yet now isolated in an impoverished countryside, such key reserves are a magnet for predators.  Too many nature reserves are in poor condition and are clearly acting as a ‘sink’ for the species.  Even worse, habitat is created to attract key species but the issue of predation ignored as it is considered too difficult for the organization to handle.

So how do we tackle the problem of high levels of predation on nature reserves yet distance ourselves from the likes of intensive game bird operations?  Killing anything has to be the option of last resort.  First must come habitat design and management, to reduce the impact of predators.  Many of our older traditional reserves desperately require a design re-think and tweaks to improve the situation may be relatively easy to implement. Secondly, non-lethal methods of dissuading predators need to be considered.  The best options here may be predator-exclusion fences (see below).  Ok, they may look a bit ugly and we need to improve design and positioning but their impact can be substantial.  Finally, if we come to consider lethal control (and this is essentially foxes), it needs to be based on a clear understanding of the ecology of both predator and prey.  It also needs to be undertaken effectively and professionally. We do not want to, nor is it possible to, completely remove predators but the aim should be to create a window of opportunity for key threatened species to reproduce where the options for safe nesting are limited.  An ineffective predator control programme achieves nothing.

Is it another silent spring on your local reserve?  Think it through and start the journey to noisy, smelly success.

Below: predator-exclusion fence set within a ditch at Wallasea (ditch yet to be flooded).

A short video on a predator exclusion fence trial at Titchwell - here


David Kelly said...

Good blog again, this year's first successful fledging of Little Gulls in the UK, at Loch of Strathbeg, was down to exactly the kind of measures you describe here.

Grumpy Ecologist said...

Thanks David. Yes, the installation of an predator exclusion fence (mainly for Otters) at Strathbeg has been very successful. Tern and gull numbers now increasing. We hope to extend the limit area protected when funds become available.