Managing water for waders

blog L sittingYour task, should you choose to accept it, is to turn farmland into a haven for breeding waders. The only tools you have at your disposal are tractors and cows and we will give you permission to pump water out of nearby rivers when conditions allow. That’s how it started. These days the diggers look big enough to use on a motorway construction site!

If your aim is to maximise the number of pairs of breeding waders on your lowland wet grassland farm or nature reserve, then one of the key issues is to get the water levels right. The first  part of this blog focuses on providing an appropriate mix of ditches, pools and grazed grassland for species such as Lapwing, Redshank and Snipe and then keeping everything wet enough (but not too wet) during the important chick-rearing season.

The second part of the blog is not just about maximising the number of breeding waders on a nature reserve. It’s also about working with neighbouring farmers, in order to secure fresh water supplies for the future and to reduce the risk of salt-water inundations, associated with sea level rise. In the long-term, stakeholder engagement has proved far more important than habitat management, as you will read below.

Understanding water levels

When developing lowland wet grasslands for waders, an extra five cm of late-winter rain can make a huge difference, especially if you can capture as much as possible of the rain that falls or can draw water from a swollen river. Mark Smart, the former Senior Site Manager for the RSPB’s Berney Marshes and Breydon Water reserve in East Anglia, understands grazing marshes and how to capture and distribute water, in order to provide the muddy edges where wader chicks find insects. An aerial photograph of Berney Marsh shows how Mark has designed a special landscape to capture winter rain – one that is ideal for Lapwings and other waders.

Mark has taken the lessons he has learnt on RSPB nature reserves and shared them widely, a contribution to conservation that earned him one of the 2018 Marsh Awards for Wetland Conservation from the Wildfowl & Wetland Trust.

From wheat and barley to ducks and waders

blog cow eatingThe marshes of the Norfolk Broads have been drying out for 2000 years. By the 1970s, and after over 400 years of farming, the Halvergate Marsh complex was on the point of being fully drained and by 1985 much of the wet grassland in which waders formerly bred had already been lost and turned into arable fields. At this point, the RSPB made its first purchase of land, as they tried to retain at least some of the threatened habitat which is so important to winter wildfowl and summer waders. At the same time, campaigning by local and national conservationists secured legal protection for the unique Broadland scenery and the species that rely upon the habitats it contains, thereby halting the advance of the combine harvesters.

The importance of Halvergate Marshes for wildlife has long been known, and in 1987 it became the site of the UKs first Environmentally Sensitive Area – the prototype for subsequent agri-environment schemes. Lowland wet grasslands are traditionally drained using ‘footdrains’ – narrow, shallow channels that connect low-lying parts of the fields with surrounding ditches, in order to drain them.

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The muddy edges of a footdrain

These same footdrains can be used to hold and manage surface water levels within fields, by blocking the ditch connections with sluices. In the 1990s, Mark pioneered the design and deployment of footdrains on lowland wet grasslands, and the kit needed for their construction. Through his skills, enthusiasm and collaborations with grassland managers throughout lowland England, footdrains and the water that they can contain are now a common sight. Many generations of wader families have enjoyed the invertebrate food that footdrains support.

The breeding season for waders is very short – with the first Lapwing claiming territories in March and most chicks fledged by the end of July. Outside these months, these wet grasslands provide excellent grazing for geese and ducks in the winter and cattle in the summer. The task of nature reserve managers is to work with graziers to try to ensure that cattle deliver appropriate sward heights for winter wildfowl and summer waders.

Not just water

fence 2By creating a hot-spot for nesting birds, within an intensively-farmed landscape, land-managers also produce a food-rich area for predators, attracted in by concentrations of eggs, chicks and sitting adults. Restricting the activities of species such as foxes and crows is an important part of the role of an RSPB warden, carried out through site management and active control measures. By focusing these activities in the winter period, the RSPB’s Halvergate Marshes team are able to stop corvids and foxes from setting up territories within the area that is managed for breeding waders. Electric fencing can help to prevent foxes moving onto the site in spring, while changing the way that core wader areas are managed helps to reduce fox/nest interactions by, for instance:

  • Adding shallow ditches in the right places can break up the site into compartments and reduce the likelihood that nests will be predated.
  • Leaving areas with long grass, that is good for small mammals and the mustelids and foxes that prey upon them, can change the focus of hunting activities.
  • Erecting temporary fencing, during at least the early part of the nesting season, can both provide protection and potentially increase the synchronicity of nesting attempts and hence the ability of birds effectively to mob predators.

blog L chickThere is more about these measures in these blogs, with links to papers from the RSPB and University of East Anglia team of conservation researchers:

There is annual management of the Berney site too, with foot-drains to be re-cut, spoil to be spread in ways that can provide a mix of water-levels and more muddy edges, and rotovation of some areas to increase the diversity of habitats. These techniques might seem rather different to the ones that are used by farmers but many of the other operations at Berney are the same as would be seen outside nature reserves, with fences to mend, stock to manage and creeping thistle and rush to ‘weed-wipe’.

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Rotovation, carried out in dry conditions, adds heterogeneity and creates bare, muddy areas

Measuring success

The development of Berney Marshes has been hugely successful. Back in 1987, there were only 13 pairs of wader breeding on the site – nine pairs of Redshank and four of Lapwing. The total for 2019 looks like being about 270 pairs – over twenty times as many.

blog RK graphRedshank: The graph alongside illustrates how Redshank numbers have changed across the decades. At the same time as Breeding Bird Survey (BTO, JNCC & RSPB) for England results revealed huge declines, with a loss of nearly half in the period 1995-2017, Redshank pairs on Berney Marshes have been increasing. Even on this site, there is a suggestion that the peak number of pairs may be in the past. Given the pressures on breeding Redshank on saltmarsh habitats (blog: Redshank – the ‘warden of the marshes’), providing breeding habitat in coastal marshes, inside sea-walls, may be particularly important. Hopefully, the latest earthworks (see later) will create more space for Redshank.

Left image below shows Redshank nest in a clump of grass. The right image shows a Lapwing nest in a newly-rotovated patch. 

blog L graphLapwing: Between 1988 and 1998, the number of pairs of Lapwing rose from 14 to 79, reaching a peak of 157 in 2010. Numbers vary, according to spring weather and water levels, with between 83 and 130 pairs in the years 2011 to 2019. The national decline in England was 28% between 1995 and 2017 (Breeding Bird Survey) – not quite as drastic as for Redshank but still worrying. Intensive studies at Berney have shown that productivity is only high enough to boost numbers in some years. The latest project by UEA and RSPB conservation scientists involves trialling temporary electric fences to provide protection for first clutches and broods. Hopefully Berney can become a net exporter of Lapwings in most years.

Oystercatcher: There were no Oystercatchers breeding at Berney back in 1997. The peak number of pairs was 18 in 2009, with an average of ten pairs in subsequent years. Nationally, numbers in England have increased but with major declines in Scotland, which is the species’ heartland within the UK. This is discussed in an earlier WaderTales blog.

Avocet: The RSPB’s logo species has been hugely successful, nationally, with the help of protection and habitat creation. The first pair of Avocets bred at Berney in 1992 and pairs have bred in most years since then, with over thirty pairs in nine years but no pairs in 2013 or 2014. The 2019 count is 35 pairs and there is potential for further growth in numbers across the site, with the creation of more island homes (see below).

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Combined harvesters have been replaced by nesting Avocets

Snipe: Despite all of the excellent habitat creation work, there have never been more than 8 pairs of Snipe recorded on Berney and only between 0 and 3 pairs in each of the last ten years. The underlying soils at Berney are clay-based, which may not suit this species.

Sharing the knowledge

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Redshank chick: science is an important feature of the work at Berney

Although it’s great that the RSPB has been able to buy and develop land for breeding waders in the Yare Valley, the impact of their work has been far larger, thanks to management agreements with other landowners. Mark Smart and the RSPB have set up Broads Land Management Services, to deliver wet grasslands that attract the top tier of conservation payments for farmers working in the Broads. Much of the recent work has been part of the Water Mills and Marshes Project, funded by HLF and led by the Broads Authority. Using specialist ditch-cutting and spoil-spreading equipment, the team has been able to create wet features within top-quality grazing fields. This is not just a local initiative; the kit and the advice have had impacts on farms and nature reserves across the country.

For his work for wetland conservation, Mark Smart received a Marsh Award for Wetland Conservation from the Wildfowl & Wetland Trust in 2018. “Mark Smart received his award for his 17 years managing RSPB Berney Marshes in the Norfolk Broads. Over this period, he brought together landowners, conservationists, local authorities and scientists to improve the marshes for wildlife. Today more than 300 pairs of wading birds nest there each spring, and more than 100,000 waterbirds return to it each winter.”

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Illustrations above shows work that has been completed at Somerleyton in Suffolk and a newly-fledged Lapwing.

blog DutchWorking with Jen Smart, who was a Principal Conservation Scientist at the RSPB’s centre for Conservation, Mark has added a Dutch dimension to the RSPB’s advice work by co-authoring Meadowbirds on the horizon of southwest Friesland.  This report has just been published by the International Wader Study Group.

Climate – ‘the new normal’

Fresh water is an increasingly important commodity in East Anglia – for farmers and for nature reserve wardens, looking to maximise agricultural and wader chick production. More extreme weather patterns are already producing periods of drought and intense periods of rain, while a rising sea-level is increasing the salinity of rivers and limiting extraction opportunities. Broadland farmers are looking for a reliable water supply, the Environment Agency is looking for ways to reinforce sea defences and for places to store fresh water, in order to avoid flooding, and the RSPB wants to hold more water in the late winter that can be used to keep areas wet in the early summer. With some lateral thinking, many of the needs of these key stakeholders can be met in partnership projects, as shown below

The Environment Agency’s need for material to raise sea defences provided Mark Smart with an opportunity to provide more pools and scrapes for breeding waders. It was a win-win solution; free habitat creation work for the RSPB and minimal movement of the clay and top-soil that the Environment Agency needed. In the images below, you can see this work in progress and the islands that are now being used by nesting Avocets.

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The most recent project is an ambitious water storage and flood reduction scheme for the whole of Halvergate Marsh. This will keep salt water out of these important grazing marshes and store fresh water for summer use. The £2 million Halvergate Marshes Water Level Management Improvement Scheme is a joint initiative, funded by DEFRA and delivered by the Water Management Alliance. The project involves a large number of stakeholders, including the Broads Internal Drainage Board, RSPB and neighbouring farming estates.

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The Water Level Management Improvement Scheme is a huge undertaking, with 8 km of new ditches, 240 piped culverts and 12 big sluices, that will create storage for 60,000 cubic metres of fresh water and systems to distribute this water over the course of a dry East Anglian summer. One of the most impressive features of the project, illustrating the imagination of the design team, is the Higher Level Carrier, a ‘flyover’ ditch system that passes over the top of existing wet grazing land to get water to some of the driest part of Halvergate Marshes (left picture below). This high-level water transportation route was constructed using locally-sourced clay, thereby creating shallow pools around which yet more waders are already nesting.

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When designing this project, the opportunity was taken to develop opportunities for birdwatchers to see the birds that will be drawn into the wettest areas, by making sure that the ‘best bits’ are close to public access points on the Weavers’ Way, the 61 mile (100 km) long-distance path running from Cromer to Great Yarmouth.

Aspirations

Mark Smart has not finished yet! Plans are afoot to develop the RSPB’s land that is closest to Great Yarmouth, recently purchased using a WREN grant. If agreed, this can provide an alternative, safe high-tide refuge area for tens of thousands of waders and wildfowl that roost on the mud and saltmarsh at the mouth of the Yare. Their current high-tide refuge is threatened by sea-level rise and developments proposed for the outskirts of Great Yarmouth.

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This proposed roosting area will be part of an extension to the Halvergate Marshes Water Level Management Improvement Scheme, which will add another 10,000 cubic metres of water storage. Alongside flood alleviation and fresh-water conservation, this scheme will create fifty hectares of additional shallow wader and waterfowl scrapes adjacent to Breydon Water.

blog Wood spThe new scrapes should not only attract wintering and breeding birds but also many passage waders, such as the Wood Sandpiper pictured to the right. The whole scheme has the potential to be another win-win-win-win, for the owners of low-lying properties, for Broadland farmers, for internationally important bird populations and for local and visiting birdwatchers.

Read more

Information about the RSPB’s Berney Marshes & Breydon Water reserve can be found on the RSPB’s website. Click here

There is information about the Water, Mills and Marshes project here.

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GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

Chicks and ticks

pic chick on move

How do ticks affect Golden Plover chicks? By utilising data from an existing study, David Douglas and James Pearce-Higgins have discovered that Golden Plover chicks that carry more sheep-ticks Ixodes ricinus have a lower chance of survival. Their findings are written up as a paper in Bird Study. The work is only based on a small sample and the data don’t identify the mechanism that leads to increased mortality but, given the current interest in the biological effects of ticks, the findings are interesting.

Costs of carrying ticks

Carrying ticks has three potential effects on wader chicks

  • Ticks suck blood, which could be costly.
  • Ticks can introduce diseases, via tick-borne bacteria and viruses.
  • There may be effects on feeding efficiency, via impaired vision, hearing etc.

Sheep ticks act as vectors for a variety of pathogens, including the louping ill virus (LIV) which can affect a range of domestic and wild mammals, as well as wild birds. LIV is known to cause high mortality of Red Grouse chicks but there has been no previous assessment of the effects of sheep ticks on other moorland birds, such as breeding waders. It should be noted that wader chicks eat ticks – so they are not ‘all bad’.

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Ticks can clearly be seen on the unfeathered lower eyelid of this young chick. There are smaller ticks attached to the gape at the base of the beak as well.

All sorts of things could influence the probability of tick infestation in birds:

  • Ticks may be able to survive better in warmer conditions.
  • Tick numbers can be affected by the number of mammalian hosts.
  • Mammal to bird transfer could be affected by land management and habitat structure.

Ecological interactions between ectoparasitic ticks and waders are not well understood. Given possible increases in tick abundance with climate change, the authors of the new study felt that it would be useful to test whether ticks have detectable effects on the Golden Plover chicks that carry them.

Spotting an opportunity

The Golden Plover chicks that provided the data used in this paper were caught as part of a wind farm study at Gordonbush in northern Scotland, a site made up of 33 km2 of blanket bog. There is more information about the study in these two papers:

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Gordonbush, prior to the development of a wind farm

Tick numbers on Golden Plover chicks were collected at the time of ringing (within 24 hours of hatching) and during subsequent recaptures. Recapture was facilitated by locating tagged birds using radio-location. On each capture, chicks were weighed and the number of ticks visible on the bare parts of the head (around the eyes and bill) were counted. Most ticks attach themselves to the bare parts of the head and neck.

Variation in tick loads on Golden Plover chicks

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Incubating adult. Golden Plovers commence primary moult at the start of (or before) incubation. Read more here.

The number of sheep-ticks found on these Golden Plover chicks was higher than those previously reported for waders but were within the range of those found on Red Grouse on moorland. Previous wader studies had been focused upon areas with sheep, which were routinely treated to reduce tick infestations. In the current study it was found that:

  • 90% of chicks were carrying ticks, with between 1 and 12 ticks being found on each affected Golden Plover chick. The highest tick-load was found in mid-age chicks.
  • Tick loads were higher during periods with warmer maximum temperatures and when chicks were estimated to have moved through taller vegetation between recaptures.
  • Chick growth rates were depressed by high tick-loads, especially when temperatures were warmer.
  • Of the 21 chicks, 4 fledged, 13 died and the outcomes for the other 4 were unknown. Half of the deaths appeared to have been due to predation and half to starvation/exposure.
  • Chicks that were heavier (for their ages) were more likely to survive. Those with higher tick loads (for their ages) were less likely to survive.

With the small sample size, it was not possible to detect a correlation between tick load and chick growth rates but low survival was correlated with high tick-loads. This had not previously been documented for waders.

Implications for wader conservation

pic red deer

Gordonbush is an area where there is no grazing by domestic animals so the likely mammalian tick-hosts are Red Deer in particular and also Mountain Hare. The correlation between warmer weather and tick numbers, found in this study, could be explained by increased tick activity, while the link to taller vegetation may well be explained by ticks seeking damper microhabitats. In their discussion of the results, the authors suggest potential ways that ticks and waders, of different ages, might interact. Anyone looking to expand the work, in order to understand the mechanics of tick infestation, is likely to spend more time looking at ticks than waders!

pic Curlew
Could ticks be reducing survival probabilities for  young Curlew?

The authors of this paper were not able to test for the presence of disease (such as LIV) in their Golden Plover population but this is a plausible cause of the increased probability of mortality. In a study in Yorkshire by Newborn et al. (2009), no evidence was found of LIV in wader chicks, whereas it was present in 3.6% of a sample of Red Grouse chicks at the same sites. Newborn and colleagues report that a single Eurasian Curlew chick has previously been recorded to be seropositive for LIV. In the Newborn study, the lowest incidence of ticks among waders was in Lapwings (6% of broods), followed by Golden Plover (47% of broods had ticks) and Curlew (91% of broods). There is a hint, in these data, that ticks might more commonly attach themselves to wader chicks that are found in taller vegetation.

Despite high tick loads on chicks, and the correlation with lower chick survival, the overall percentage of Golden Plover chicks known to fledge in the Gordonbush study (19%) is comparable with other studies. Perhaps ticks are only causing the deaths of chicks that would have died anyway?

pic Red Grouse

The authors suggest that no case should be made for tick-control, to help breeding waders, until it is clear whether tick-based chick mortality limits Golden Plover and other wader populations on moorland. In the paper, they argue that previous attempts to reduce moorland tick abundance and tick loads on Red Grouse have failed to detect convincing evidence of improvements in grouse survival, breeding success or post-breeding densities.

A range of methods have been deployed in attempts to reduce moorland tick abundance and tick loads on Red Grouse, including reducing densities of mammalian tick hosts (Mountain Hare and deer) and deploying acaricides (as used in sheep dips). See this link to material from GWCT on ticks and Red Grouse.

In conclusion

pic older chick

Work at a single site over two years appears to have documented a level of tick infestation in Golden Plovers that is associated with chick mortality. It is not clear how chicks are being affected, particularly given that there is insufficient evidence thus far that ticks affect chick growth rate.

The authors collected the data analysed in this paper for other studies – the focus was not on tick effects – and they hope that funding might be found for future research focusing upon the associations between ticks and waders, other birds and other animals. Until that happens, it would be useful if shorebird biologists who repeatedly handle wader chicks, in order to measure growth and survival rates, could routinely record the presence or absence of ticks.

Given that warming temperatures could lead to increased tick abundance, this seems to be a good time to discover more about tick behaviour, the importance of ticks as a food source for wader chicks and whether tick-loads are reducing growth rates and fledging success in other wader species.

Paper

This research is published in the BTO journal Bird Study. Click on the details below to link to the full paper:

Variation in ectoparasitic sheep tick Ixodes ricinus infestation on European Golden Plover chicks Pluvialis apricaria and implications for growth and survival. David J. T. Douglas and James W. Pearce-Higgins. Bird Study. June 2019.

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GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton