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Providing evidence to improve practice

The journal, Conservation Evidence

Our online journal publishes research, monitoring results and case studies on the effects of conservation interventions. All papers include some monitoring of the effects of the intervention and are written by, or in partnership with, those who did the conservation work. It includes interventions such as habitat creation, habitat restoration, translocations, reintroductions, invasive species control, and education or integrated conservation development programmes, from anywhere around the world.

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A volume is created each year with peer-reviewed papers published throughout the year. We now accept Short Communications as well as standard papers.

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Volume 2

A combination of rat Rattus baiting, trapping and remote fired detonators was used to protect the eggs of the endangered flightless parrot, the kakapo Strigops habroptilus, from rat predation. The detonators were twice fired in the presence of rats, which left on both occasions. The incubating kakapo showed no evidence of reacting to detonations.

To help resolve the conflict between pygmy cormorants Phalacrocorax pygmeus and fish farmers, the birds were scared away from Bet She'an Valley before the breeding season started. The cormorants have subsequently relocated to other, safer breeding sites.

There appears to be a risk of kakapo Strigops habroptilus eggs chilling when the female is away feeding. Since 1997 all kakapo nests had heat pads applied when the female was off the nest and supplementary food was provided to reduce the time necessary to forage. No mortality events have since occurred that can be attributed to chilling.

A volunteer 'kakapo nest minder' protocol was developed. Conservation volunteers enabled management of nests on an individual basis to a level where mortality of chicks was negligible. In 2002 they managed 24 nests which produced 26 kakapo chicks, of which 24 fledged. In addition significant cost savings were achieved using volunteers.


Experiments with hidden transmitters showed that people undertaking radio-telemetry of kakapo Strigops habroptilus, often walked over the transmitter prior to locating it. In a real situation, this could equate to a risk of causing nest failure through trampling of a nest or disturbance of the incubating female. A new telemetry nest approach procedure was therefore developed to avoid potential mistakes.

Former arable land at Minsmere RSPB Reserve, eastern England, was treated with sulphur, herbicide was applied to control weeds, and seeds were sown in an attempt to create acid grassland. Soil pH was reduced and acid grassland target species dominated the vegetation three years after seeding.

Nine samples of soil were taken from former arable land at Minsmere RSPB Reserve, Suffolk, England. Sulphuric acid and iron was added. The pH of the soil was reduced, but the iron addition did not appear to have an affect on reducing the quantity of extractable phosphorus.

On former arable land at Minsmere RSPB Reserve, eastern England, sheep grazing was introduced with the objective of creating acid grassland. Seven years after the introduction of a grazing regime, the fields had lower cover and species-richness than the existing adjacent acid grassland.

An attempt was made to convert a former arable field to acid grassland. Elemental sulphur, bracken Pteridium aquilinum litter and heather Calluna vulgaris clippings were added and the area grazed with sheep. Over seven years the target acid grassland species cover increased considerably to 60.7%. Adjacent existing acid grassland had 85.6% cover of these species.

Sulphur and clippings of heather Calluna vulgaris and bell heather Erica cinerea were added to an area of former arable land with the objective of creating heathland. Nine years later these two species had both become well established.

At a coastal site in Wales, year-round cattle grazing was introduced to an area of ungrazed semi-improved grassland,which was rarely used by foraging choughs Pyrrhocorax pyrrhocorax. Grazing greatly reduced the sward height and the area became a major feeding area for chough.

At a nature reserve in Northern Ireland, feeding regimes were investigated in an attempt to attract wildfowl and other birds close to public viewing areas. Wildbird mix proved to be very attractive to ducks, especially mallard Anas platyrhynchos, who dominated and excluded other species. White millet, with smaller seeds, was less attractive to mallard but attracted black-tailed godwits Limosa limosa, teal Anas crecca and a range of other species. The birds will now feed within a few metres of the visitors observation hide.

At Leighton Moss RSPB Reserve, northwest England, bearded tit Panurus biarmicus nest boxes were designed and installed. Over 42% of the nest boxes have been occupied over the eight years of their use. Nest boxes placed over water are more likely to be used.

Three methods of New Zealand pygmyweed Crassula helmsii control were undertaken: using 'Waipuna' hot foam, spraying with Glyphos bioactive, and by smothering and burying. Spraying with either 'Waipuna' or Glyphos killed 50% of the vegetation and stopped Crassula from spreading, but did not eradicate the weed. Smothering and burying killed all plants (100% mortality), but proved very labour intensive and causes much disturbance.

Sweet chestnut Castanea sativa coppice was controlled by five different methods: repeated cutting,amcide poured into drilled holes, herbicide painting of stumps, weed-wiping of first year growth, and knapsack spraying of regrowth. The most effective and efficient method was to cut the coppice stools and subsequently knapsack spray the first year regrowth with herbicide.

A long term monitoring scheme was established to examine the mortality rate of sessile oak Quercus robur trees in an even aged forest. Of 1,835 marked trees, only 15 died in the six years of the study. It is suggested that large samples (2,000-5,000 indivivdual trees) may be required to ensure meaningful results from such studies.


Measures were undertaken to attempt to eradicate invasive rhododendron Rhododendron ponticum. Mechanical removal is quick, but expensive (£1,000/day) and has a high potential for damaging the soil and coppice stools. Manual removal is labour intensive (120 man-days/4 ha), but was less damaging and could be applied in areas in which machinery could not be used. Weed-wiping regrowth was slower but more effective (70% kill rate) than spraying (40-50% kill rate).

In an attempt to increase distribution of common cow-wheat Melampyrum pratense, turves containing cow-wheat were transplanted in April and May, and seeds were sown in July. Both methods resulted in only a few seedlings maturing to adults with some seed set but neither produced viable populations. Cow-wheat is a hemiparasite but both the host species and the ectomycorrhizal fungus requirements are unknown, and it may be that the appropriate hosts were absent.

Former cattle-grazed grassland and arable land were converted into wet grassland by raising the water level. Over the next five years the vegetation shifted towards plant communities characteristic of wet grassland.

At Berney Marshes RSPB Reserve, water levels were raised, foot drains were added, and grazing by sheep was introduced. The plant communities shifted towards communities' characteristic of lowland wet grassland. Breeding wading bird numbers increased in response to these habitat changes.

Introduced marram grass Ammophila arenaria has changed the beach profile so that for Chatham Island oystercatchers Haematopus chathamensis the flooding of nests is now a serious problem. From 1998 to 2004 nests were routinely moved upshore to save them from storm surges and high tides. During this period the oystercatcher population increased from 16 to 34 pairs.


A portable low-cost fabric pen makes it possible to 'gently release' hand-reared kakapo Stigops habroptilus, to confine kakapo undergoing veterinary treatment, to give supplementary food, and to settle translocated individuals into predetermined locations.


A faster and cheaper method of hedge-laying to benefit wildlife using a mechanical hedge laying technique has been developed. In comparison to traditionally laid hedges, those mechanically laid are broader at the base, thicker, taller, retain more deadwood and flower and fruit every year.


The effects of introducing cattle grazing to a saltmarsh on breeding redshank Tringa totanus were investigated. The density of breeding redshank did not noticeable change after introduction of grazing.

Suitable breeding areas for ground nesting waders were restored by mechanically scraping off vegetation that had colonized limestone slag banks. In response, breeding numbers of ringed plover Charadrius hiaticula, oystercatcher Haematopus ostralegus and lapwing Vanellus vanellus doubled in the year following restoration. Early successional plants also benefited.


A programme was introduced to eradicate invasive New Zealand pygmyweed Crassula helmsii by Reglone herbicide treatment. In response, 70% of pygmyweed was killed. Follow up spraying of regrowth was partially successful but some re-growth is noticed annually.


At The Lodge RSPB Reserve, an attempt was made to eradicate invasive New Zealand pygmyweed Crassula helmsii that had colonised a pond by covering with black polythene. Pygmyweed was completely eradicated but re-colonised from plants in marginal vegetation in areas not covered with polythene.

The effects of adding organic matter (barley straw) on aquatic invertebrate food supply for waterbirds in an artificial saline lagoon in eastern England was investigated. The addition of barley straw resulted in an increase in benthic invertebrate biomass the following year, but was not considered a successful long-term management strategy to boost invertebrate populations.


To restore an area of former heathland, soil nutrient levels were reduced by turf removal. Turf-stripping reduced dominance of wavy hair-grass Deschampsia flexuosa and promoted an increase in heather Calluna vulgaris.

In order to restore heathland, birch Betula trees were cleared, the humic layer was removed, and heather Calluna vulgaris seeds were spread out over the restoration area. Two years later there was a good growth of young heather plants with 5-10% cover seven years after the intial clearance, whilst some areas were dominated by wavy hair-grass Deschampsia flexuosa.


In order to restore heathland, Douglas fir Pseudotsuga menziesii and Scots pine Pinus sylvestris was removed, and thereafter three treatments were applied: i) no soil removal or seed addition, ii) seeding with heather Calluna vulgaris, iii) removal of humic layer and seeded with heather. There was little or no heather establishment in untreated areas; heather establishment and growth was good in one seeded area (15% cover) but not the other; where humus had been removed and seed added the area was dominated by common bent grass Agrostis capillaris (50% cover), Campylopus introflexus (20%) and juniper hair-moss Polytrichum juniperinum (13%); very little heather (<1% cover) had established.

To restore brown teal Anas chlorotis populations, a captive breeding and release programme has been developed. At the Moehau Kiwi Sanctuary, a first release of 60 teal had a survival rate of 45%, and the second release of 40 birds an 85% survival rate. As the survival rate of the second release was so high, the same methods will be used in the next planned release, in combination with ongoing predator control.

For The Chicken Islands group (New Zealand) a pacific rat Rattus exulans eradication programme was undertaken in an attempt to establish a safe offshore haven for many rare native species. Eradication of the introduced rats was successful, and in response, populations of several native reptiles have increased and seabird fledging success has increased dramatically.


To protect Chatham Island oystercatcher Haematopus chathamensis eggs from being trampled, stock fencing and electric fencing was applied. Only one nest was trampled by cattle, however, 13 of 19 nests that were video recorded were predated by cats Felis catus.


Dune restoration through herbicide control of invasive marram grass Ammophila arenaria and replanting with native species has resulted in dune reprofiling. This has allowed Chatham Island oystercatcher Haematopus chathamensis, an endangered species, to nest higher up the beach where they are less vulnerable to loss of clutches to high tides and storm surges.


Following predator control, in conjunction with other conservation intitatives, the number of breeding pairs of Chatham Island oystercatcher Haematopus chathamensis in a 14 km management area increased from 16 pairs to 35 pairs. These birds produced 18-35 chicks a year. In 1999 the entire global population was only 142 birds but it had increased to 320 birds by 2004.


Totals of 67 Middle Island tusked weta Motuweta isolata were released on Red Mercury Island and 80 on Double Island between 2000 and 2003. In 2005 surveys located 11 wetas on Red Mercury and 4 on Double Island. Juvenile wetas were found on both islands in 2004 and 2005 showing that successful breeding had occurred.

Former arable fields were treated by removing the topsoil, adding sulphur and applying seed-rich cuttings of heather Calluna vulgaris, bell heather Erica cinerea and western gorse Ulex gallii using a muck spreader. After soil stripping an interesting plant community developed including some less frequent or rare species. Both heather species and western gorse germinated. Soil pH a year after the sulphur addition was 5.6 where applied at rate of 4t/ha and 4.2 where applied at 8t/ha.


Following predator control the population of New Zealand fairy tern Sterna nereis davisae increasesd from five breeding pairs to 35-40 individuals.

Juvenile flax snails Placostylus ambagiosus experience high mortality from introduced predators. Snails were kept in a terrarium with constant high humidity, regular moisture and a relatively constant temperature. Leaves, especially from karaka tees Corynocarpus laevigatus, were provided as food but the juveniles also fed on the algae allowed to build up within the terrarium. They eventually bred successfully and grew faster than in the wild.


Following removal of Norway rats Rattus norvegicus and rabbits Oryctolagus cuniculus from Motuhora (Whale Island), 32 adult tuatara Sphenodon punctatus were introduced in 1996. They produced at least two clutches of offspring, and about 50 individuals were present when surveyed in 2005.

Two hundred wooden refuges were provided for the Auckland tree weta Hemideina thoracica. Within six months over half were used, 52 weta were transferred to Korapuki Island by plugging then translocating these refuges. After five years, there were over 500 individual tree wetas present on Korapuki.


Three hibernacula were created for common lizards Lacerta vivipara in an area set aside for a suburban nature conservation area in the town of Lowestoft, eastern England. Six months later in the spring following construction, lizards were present in small numbers around each hibernaculum. The lizards apparently preferred to use natural gaps for entry rather than the entrance pipes provided.

Off the coast of New Zealand, small quantities of shark liver oil dripped onto the water surface behind a fishing boat deterred pelagic seabirds from taking bait on long-line hooks.


An area dominated by purple moor grass Molinia caerulea was burnt, flail mowed, heather seed was added, and then grazed. Heather Calluna vulgaris seedlings were observed the next summer and grazing kept Molinia growth in check.


An area of silver birch Betula pendula (40% cover) was cleared during the winter of 1995-1996. Two summers later, the cleared area and an adjacent area of open heath were sprayed with Asulox herbicide to control invasive bracken Pteridium aquilinum growth. Seven years after the last spray treatment, bracken was dominant throughout the area (median cover in sample plots 80%; cover estimate range 40%-90%). Whilst achieving short-term success, longer term evidence therefore suggests that bracken management needs to be ongoing at this site.

At a site in southern England in September 2004, about 4 ha of mature, dense, non-native, maritime pine Pinus pinaster was cleared using a shear-head timber processor. One year later in August 2005, the cleared area was predominantly covered in purple moor-grass Molinia caerulea (approx. 80% cover). The remaining 20% was either bare ground (approx. 15%) or mature heather Calluna vulgaris and gorse Ulex plants (less than 5% cover) present prior to clearance, but no heather seedlings were found. There was no evidence of any pine regeneration.

In August 2004, an area of just over 1 ha of dense, mature Scots pine Pinus sylvestris was cleared using a shear-head timber processor. Prior to the clearance, the area supported little heathland vegetation and was predominantly bare ground with some bracken Pteridium aquilinum underneath the dense pine canopy. One year after the clearance, heather Calluna vulgaris seedlings had become established. Evidence suggests that control of bracken and tree seedlings may be required as part of long-term management in order to restore and maintain an open heath.


Approximately 0.5 ha of dense, mature Scots pine Pinus sylvestris and rhododendron Rhododendron ponticum was cleared using a shear-head timber processor. Prior to clearance the area under the canopy supported little heathland vegetation. One year later, heather Calluna vulgaris seedlings had become established; other heathland vegetation included purple moor grass Molinia caerulea and cross-leaved heath Erica tetralix. There was also evidence of vigorous rhododendron regrowth from the cut stumps.


Approximately one third of a hectare of mature heather Calluna vulgaris was burnt in January 2000. Five years later, the burnt strip was revisited. It had fewer heather flowers and the sward was shorter (20-25 cm) than the surrounding vegetation (35-40 cm). Bristle bent grass Agrostis curtisii was more abundant (25% cover) than in adjacent unburned areas (5%).


A forage harvester was used to cut swathes of heathland vegetation at a site in southern England to increase habitat heterogeneity. Areas selected were predominantly dry heath or on the margins of humid heath and were cut to ground level. Six years later the cut areas were still clearly visible. In a humid heath area purple moor-grass Molinia caerulea had been greatly reduced, heather Calluna vulgaris had increased slightly, and open patches of bare ground (important for early successional plants) were present. On dry heath, heather cover was reduced substantially but the shorter and more open sward had allowed lichen communities to develop.


On a heathland in southern England, mature gorse Ulex europaeus was coppiced and the area fenced to prevent rabbit Oryctolagus cuniculus browsing in an attempt to create a varied gorse age structure. Twelve years later little gorse had regrown from the cut stumps and the cleared area had been invaded by bracken Pteridium aquilinum.


Approximately 0.5 ha of dense Scots pine Pinus sylvestris and maritime pine P.pinaster woodland was cleared using a shear-head timber processor with the objective of restoring heathland. Prior to clearance the area supported little heathland vegetation and was predominantly bare ground with some bracken Pteridium aquilinum, underneath the thick pine canopy. One year after clearance, there was deep litter layer (7-8 cm), little regeneration of heather Calluna vulgaris, and bracken was becoming dominant.


In January 2002, with the aim being to reinstate heathland vegetation, an area of 0.75 ha was cleared of Scots pine Pinus sylvestris and some maritime pine P.pinaster trees. Prior to clearance the area supported little heathland vegetation, predominantly comprising bare ground with some bracken Pteridium aquilinum. Three and a half years after clearance, the area supported a range of common generalist, non-heathland plant species, and was being invaded by silver birch Betula pendula saplings.


A number of pine Pinus trees were ring-barked using either single or double cuts, two trees also had their crown removed. One to two years later, all the ring-barked trees were still standing. The only two which had died were the ones with their crown removed. The remaining trees were all alive, but had some dead needles and needles showing signs of discolouration. There was no clear difference between trees cut using a single or a double cut.


Two adjacent mature Scots pine Pinus sylvestris trees were ring-barked using a chainsaw. Five years later, both trees had died. One tree had blown over just above the ring-bark cuts, leaving a jagged stump 1.25 m high; the other tree had lost its crown, resulting in 10 m of standing deadwood. Saproxylic invertebrates had colonised and great spotted woodpeckers Dendrocopus major had used the taller ring-barked stump for nesting. This management method proved to be a low-cost and easy way to produce standing deadwood.

During the winter of 1995-1996 on a heathland in southern England, 1.6 ha of invading silver birch Betula pendula (40% cover) and gorse Ulex europaeus were cleared using chainsaws and burnt on site. Ten years later, the cut birch and gorse stumps were still visible; the area was largely covered in dense bracken Pteridium aquilinum (average cover of 70% over 5 plots), the only gaps being the fire sites (predominantly bare) and a few patches of purple moor grass Molinia caerulea. Little heather Calluna vulgaris was present and there was considerable evidence of birch regeneration, suggesting that further management would be necessary to prevent invasion by scrub.


In 1991, 5.7 ha of Scots pine Pinus sylvestris scrub was removed from a heathland in southern England. Trees with diameters less than 25 cm were cut using bow saws and loppers; mature trees were left untouched. Fourteen years later, the area could still be identified by the presence of cut stumps; considerable pine regeneration (330 trees/ha) was apparent as there had been no ongoing management.


Two different herbicides were used to treat young Rhododendron ponticum plants on an area of heathland in June. Three months later, of 157 plants sprayed with Glyphagen (Roundup), all but 11 had died (93% kill rate), while of 161 plants sprayed with Garlon with additions of Mixture B (a wetting agent), all but five had died (97% kill rate).


During the winter of 2000-2001, approximately 2.4 ha of dense (75-100% tree cover) and 0.6 ha of medium (25-50% tree cover) birch Betula was cut and removed. In August 2002, the cleared birch had regenerated resulting in a dense stand of 2 m high birch. The regrowth was sprayed with Timbrel using knapsack sprayers. The regrowth kill rate of sprayed areas was 100%; no regrowth was subsequently recorded.


Scrub and trees were removed from overgrown clay pits at a nature reserve in southern England. Prior to management the maximum counts of southern damselfly Coenagrion mercuriale was 40-70 adults annually, but this increased to around 150-200 adults after management opened up the pools.

An area of about 13 ha of former open heathland in southern England was cleared of Scots pine Pinus sylvestris, maritime pine P.pinaster and birch Betula spp.; prior to management it contained 50-75% scrub and mature tree cover. Clearance was conducted using chainsaws; brash was burnt. Five years later, there was considerable evidence of pine regeneration (2,600 seedlings per ha). To maintain open heath, control of tree seedlings is required after tree clearance.


At a nature reserve in central England, after failure of smaller pools dug to provide long-term white-faced darter Leucorrhinia dubia breeding habitat, a larger 7 x 7m pool was created in 1992. Breeding by white-faced darters was confirmed in 1995 and they have since bred annually with 54 individuals recorded in 2003.

At a National Nature Reserve in the Norfolk Broads (eastern England), between 1986 and 1998, 1,600 m of new dykes were excavated in the winter months. Seven of these 12 dykes were subsequently colonised by Norfolk hawker Aeshna isosceles dragonflies (a species of conservation concern in the UK).



Four shallow bays, each about 3 x 5 m, with a rear vertical face of 30 cm, were dug to attract ground-nesting bees and wasps. All four were colonised in the first year and 80 solitary bee and wasp species have been recorded to date (2004). Two scarce heathland mosses also colonised the site and the bays were frequently used by common lizards Lacerta vivipara for basking.


Ship rats Ratus rattus were eradicated from the 9.3 ha Goat Island in 1994; however, rats were redetected in 1996. From April to June 2005 using between 35 and 51 traps were deployed. Subsequent to trapping, 49 poison bait stations were established across the island on 23 June 2005 to assess if this eradication had been successful; only one was touched. Tracking tunnels and waxtags were left on the island, but with no signs of use. It seems that eradication was achieved. Gnaw marks were subsequently discovered in a waxtag at the site where reinvasion was most likely but there were no further signs over the next two months.