Citation: Babcock and Booth (2020) Using Decoys and Sound Lures. Tern Conservation Best Practice. Produced for “Improving the conservation prospects of the priority species roseate tern throughout its range in the UK and Ireland” LIFE14 NAT/UK/000394’
Last updated: October 2020
This is a live document we update regularly. If you have comments and suggestions, please email Chantal.Macleod-Nolan@rspb.org.uk
Last updated: October 2020
This is a live document we update regularly. If you have comments and suggestions, please email Chantal.Macleod-Nolan@rspb.org.uk
| Babcock and Booth (2020) Using Decoys and Sound Lures. Tern Conservation Best Practice. |
Key Messages
- Decoys and sound lures (often both together) are commonly used to try to attract terns to new or restored habitat or to specific areas e.g. inside an anti-predator fence.
- Decoys and sound lures should only be used when the habitat is suitable and there is a low perceived risk of predation, disturbance, pollution or other hazards.
- Social attractants are most useful in cases where there are relatively few terns present or little competition for space. Near large tern colonies or where there is displacement of terns, for example by increasing numbers of gulls, new habitats are often readily colonised without attractants.
- Making and/or painting decoys can be a useful education and community engagement activity.
Information
A decoy is a model of a species used to attract wild birds, usually members of the same species to a particular area. A decoy is not necessarily a precise replica, the level of accuracy required depends on the species, but should imitate the size, shape, typical posture and major plumage features of the species. It needs to be made of fairly robust materials depending on the length of deployment, examples have been made from plastic, fibreglass, resin, ceramics, and wood, or for short term use, stuffed specimens. Decoys are used by hunters, researchers trapping birds, and by conservationists, to attract a wide range of species including ducks, waders, albatrosses, Ascension frigatebirds Fregata aquila, Atlantic puffins Fratercula arctica and tern species.
A sound lure is a device playing sound recordings of bird songs or calls, normally to attract adult birds. These can be used to attract colonial birds to a breeding habitat (although are also used as a survey method e.g. storm petrels, and sometimes by birdwatching tour guides to attract territorial birds for viewing by playing the call of a potential rival or common predator to induce a mobbing response). Sound lures played at a natural volume are thought to be most effective.
Decoys and sound lures to attract wild birds to suitable breeding habitat are generally considered to be most effective when used simultaneously. They are effective for colonial species which use the presence of conspecifics to indicate good quality, safe breeding habitat and which may also derive other benefits from breeding in a colony such as protection from predators, shared information about foraging opportunities and for unpaired individuals, increased mate choice. These additional benefits of colony-nesting are not of course, conferred by a simulated colony until the number of individuals builds up to create a critical mass. It is important to actively attract birds by these methods only in safe breeding areas where predation risk is low.
The colonial nature of tern species combined with a propensity to move between sites in response to habitat loss or to low breeding success, may predispose them to be responsive to management based on social attraction. If there are terns already breeding in the area, visual or audio attractants may not be necessary, especially if the existing nesting habitat is overcrowded or dominated by gulls. However, decoys and audio lures can be useful for sites with a lower density of birds in the vicinity, to attract birds to newly created areas of habitat or rafts, or to attempt to persuade birds to breed in a specific place (such as a fenced area or area safe from high tides). They may prove particularly attractive to failed breeders relocating from another site, or birds prospecting for a new colony.
Using decoys and lures involves trying to affect the behaviour of a wild bird, which requires consideration of any legal or licencing issues. In the UK, roseate terns Sterna dougallii and little terns Sternula albifrons are Schedule 1 species, specially protected from disturbance through the Wildlife and Countryside Act (1981). Using decoys or lures on a new site with no Schedule 1 species present does not require a disturbance licence. However, if Schedule 1 species arrive at the site and show signs of breeding such as courtship activity including displaying, presenting food and nest scraping, then a disturbance licence, issued by the relevant statutory body in England, Scotland, Wales or Northern Ireland, is required. If the site is a Site/Area of Special Scientific Interest (SSSI/ASSI) or otherwise designated, permission will also need to be sought from the relevant statutory authority. The requirement for any consents from the appropriate licensing body should be arranged well in advance of any work. Landowner agreement is also likely to be required.
Decoys are available from a number of commercial sources (mainly in North America) including Mad River Decoys and Restoration Decoys but are relatively expensive, particularly if large numbers are required. Two techniques for making decoys are set out in Appendix 1 and Appendix 2 and some notes on making sound lures are included in Appendix 3.
Where decoys and lures are deployed, it would be useful to record how they were set out including numbers and spacing and the species response. Reports on which arrangement is most successful vary, but a good general rule might be to deploy decoys in larger (10+), widely spaced (1.5 m+) groups which includes both single birds and pairs. Placement of decoys should leave area of the best quality tern habitat available. Facing decoys into the prevailing wind as terns usually do, is logical but the effectiveness of this does not appear to have been scientifically tested.
A decoy is a model of a species used to attract wild birds, usually members of the same species to a particular area. A decoy is not necessarily a precise replica, the level of accuracy required depends on the species, but should imitate the size, shape, typical posture and major plumage features of the species. It needs to be made of fairly robust materials depending on the length of deployment, examples have been made from plastic, fibreglass, resin, ceramics, and wood, or for short term use, stuffed specimens. Decoys are used by hunters, researchers trapping birds, and by conservationists, to attract a wide range of species including ducks, waders, albatrosses, Ascension frigatebirds Fregata aquila, Atlantic puffins Fratercula arctica and tern species.
A sound lure is a device playing sound recordings of bird songs or calls, normally to attract adult birds. These can be used to attract colonial birds to a breeding habitat (although are also used as a survey method e.g. storm petrels, and sometimes by birdwatching tour guides to attract territorial birds for viewing by playing the call of a potential rival or common predator to induce a mobbing response). Sound lures played at a natural volume are thought to be most effective.
Decoys and sound lures to attract wild birds to suitable breeding habitat are generally considered to be most effective when used simultaneously. They are effective for colonial species which use the presence of conspecifics to indicate good quality, safe breeding habitat and which may also derive other benefits from breeding in a colony such as protection from predators, shared information about foraging opportunities and for unpaired individuals, increased mate choice. These additional benefits of colony-nesting are not of course, conferred by a simulated colony until the number of individuals builds up to create a critical mass. It is important to actively attract birds by these methods only in safe breeding areas where predation risk is low.
The colonial nature of tern species combined with a propensity to move between sites in response to habitat loss or to low breeding success, may predispose them to be responsive to management based on social attraction. If there are terns already breeding in the area, visual or audio attractants may not be necessary, especially if the existing nesting habitat is overcrowded or dominated by gulls. However, decoys and audio lures can be useful for sites with a lower density of birds in the vicinity, to attract birds to newly created areas of habitat or rafts, or to attempt to persuade birds to breed in a specific place (such as a fenced area or area safe from high tides). They may prove particularly attractive to failed breeders relocating from another site, or birds prospecting for a new colony.
Using decoys and lures involves trying to affect the behaviour of a wild bird, which requires consideration of any legal or licencing issues. In the UK, roseate terns Sterna dougallii and little terns Sternula albifrons are Schedule 1 species, specially protected from disturbance through the Wildlife and Countryside Act (1981). Using decoys or lures on a new site with no Schedule 1 species present does not require a disturbance licence. However, if Schedule 1 species arrive at the site and show signs of breeding such as courtship activity including displaying, presenting food and nest scraping, then a disturbance licence, issued by the relevant statutory body in England, Scotland, Wales or Northern Ireland, is required. If the site is a Site/Area of Special Scientific Interest (SSSI/ASSI) or otherwise designated, permission will also need to be sought from the relevant statutory authority. The requirement for any consents from the appropriate licensing body should be arranged well in advance of any work. Landowner agreement is also likely to be required.
Decoys are available from a number of commercial sources (mainly in North America) including Mad River Decoys and Restoration Decoys but are relatively expensive, particularly if large numbers are required. Two techniques for making decoys are set out in Appendix 1 and Appendix 2 and some notes on making sound lures are included in Appendix 3.
Where decoys and lures are deployed, it would be useful to record how they were set out including numbers and spacing and the species response. Reports on which arrangement is most successful vary, but a good general rule might be to deploy decoys in larger (10+), widely spaced (1.5 m+) groups which includes both single birds and pairs. Placement of decoys should leave area of the best quality tern habitat available. Facing decoys into the prevailing wind as terns usually do, is logical but the effectiveness of this does not appear to have been scientifically tested.
Figure 3. Arctic tern with of the decoys used in Maine (from Kress, 1997)
Published Research
The literature on decoys and lures suggests variable effectiveness, perhaps linked to the role of other factors in colony establishment and the range of tern species covered by the studies. A combination of management actions including predator control (particularly of large gulls), vegetation removal and social attraction (decoys and sound recordings) is often employed, so separating the relative important of these measures is often not possible.
Pynenburg et. al. (2017) tested decoys and lures to relocate breeding common terns Sterna hirundo to newly created habitat islands in a rehabilitated wetland on Lake Ontario, Canada. Three different call types (local, from elsewhere in the Great Lakes, and from the Atlantic coast of North America) were tested. In late April when terns were prospecting, decoys were placed on three islands and playback of the different calls rotated between them. A fourth island served as a control. Counts during May showed no significant difference between the effectiveness of the different call types. Nor was evidence found that the social attractants were effective. Gull control (by nest removal under permit) and availability of new habitat were the key factors. This suggests that terns were under pressure from the gull population and seeking colonisation opportunities, therefore social attractants were redundant.
Arnold et. al. (2011) attempted to test the relative importance of aural (sound recordings) and visual cues (decoys) in attracting common terns as part of a colony restoration project on Muskeget Island, Massachusetts, USA. The two-year experiment with three treatments (decoys and sound, sound only and decoys only) found that the first 50 nests to establish each year were built 10 - 100 m downwind from the speakers playing sounds of an active common and roseate tern colony. No nests were built within decoy plots and the authors concluded that sound attractants were the most influential. Behavioural observations showed that birds responded to decoys only when within range of sound. It is worth noting that in subsequent years sound lures and decoys were placed together on the island and that common terns were seen to interact with decoys even when the sound wasn’t working.
Kress (1997) describes the restoration of two tern colonies in the Gulf of Maine, USA. Common and Arctic terns Sterna paradisaea nested on about 75 islands in the Gulf of Maine in 1885, but persecution reduced the number about 16 colonies by 1900. Following legal protection, tern number increased until about 1940, when approximately 8,000 pairs each of common and Arctic terns nested on approximately 25 islands. After that tern numbers declined in Maine as herring gull Larus argentatus and great black-backed gull Larus marinus populations increased. By 1977, the Arctic tern population had declined to 3,146 pairs on 9 islands and common terns 2,095 pairs on 24 islands. Roseate terns showed a similar pattern, as numbers declined from about 275 pairs in 1931 to just 80 pairs in 1977.
On Eastern Egg Rock, a 2.9 ha, treeless island located 9 km from the shore, gull control began in 1974, at which point the island was dominated by about 200 pairs of great black-backed gulls. Each year from 1978 to 1981, 28 tern decoys, some with a head extended posture and others with a short-necked, incubating posture, were placed in suitable habitat. In 1978 and 1979, Arctic tern colony sounds were broadcast from speakers located near the decoys when terns were sighted (and in 1980 and 1981 from dawn to dusk). Both Arctic and common terns began landing with decoys soon after the attraction program started. During 1978 and 1979, terns loafed with the decoys and often interacted with them, offering fish to the models, making scrapes and parading with nesting material. During these years the terns chased off gulls and humans which approached the vicinity. By July 1980, there were 12 Arctic tern nests and 20 common tern nests, all clustered among the decoys, with the sound speaker in the middle and by the end of the season the colony had grown to 80 pairs of terns. By 1996, Eastern Egg Rock was the largest common tern colony in Maine with 1,374 pairs and roseate terns had increased to at least 126 pairs (78% of all roseate terns nesting in Maine). The Arctic tern colony on Eastern Egg Rock was small at this time, being focussed on Seal Island.
Seal Island National Wildlife Refuge is a 40ha treeless island 29 km from the mainland. Gulls completely excluded terns from Seal Island by the mid-1950s and so gull control began in 1984. Each year from 1985-1989, 50 Arctic tern decoys were set in suitable habitat and a tape recording of Arctic tern courtship calls, was played from dawn to dusk on most days. Arctic terns began landing within several days of placement of decoys, sitting among the decoys or attempting to feed them small fish. Low levels of tern activity were observed from 1985-1988. In 1989, tern numbers increased late in the season forming a colony of 16 pairs of Arctic terns and 1 pair of common terns. Late nesting suggests that the birds had failed elsewhere and made a second nesting attempt at Seal Island. By 1996, there were 956 pairs of Arctic terns and 780 pairs of common terns at the colony. A few pairs of roseate terns nested at Seal Island in 1991 and 1995 but remained a rare breeder.
The literature on decoys and lures suggests variable effectiveness, perhaps linked to the role of other factors in colony establishment and the range of tern species covered by the studies. A combination of management actions including predator control (particularly of large gulls), vegetation removal and social attraction (decoys and sound recordings) is often employed, so separating the relative important of these measures is often not possible.
Pynenburg et. al. (2017) tested decoys and lures to relocate breeding common terns Sterna hirundo to newly created habitat islands in a rehabilitated wetland on Lake Ontario, Canada. Three different call types (local, from elsewhere in the Great Lakes, and from the Atlantic coast of North America) were tested. In late April when terns were prospecting, decoys were placed on three islands and playback of the different calls rotated between them. A fourth island served as a control. Counts during May showed no significant difference between the effectiveness of the different call types. Nor was evidence found that the social attractants were effective. Gull control (by nest removal under permit) and availability of new habitat were the key factors. This suggests that terns were under pressure from the gull population and seeking colonisation opportunities, therefore social attractants were redundant.
Arnold et. al. (2011) attempted to test the relative importance of aural (sound recordings) and visual cues (decoys) in attracting common terns as part of a colony restoration project on Muskeget Island, Massachusetts, USA. The two-year experiment with three treatments (decoys and sound, sound only and decoys only) found that the first 50 nests to establish each year were built 10 - 100 m downwind from the speakers playing sounds of an active common and roseate tern colony. No nests were built within decoy plots and the authors concluded that sound attractants were the most influential. Behavioural observations showed that birds responded to decoys only when within range of sound. It is worth noting that in subsequent years sound lures and decoys were placed together on the island and that common terns were seen to interact with decoys even when the sound wasn’t working.
Kress (1997) describes the restoration of two tern colonies in the Gulf of Maine, USA. Common and Arctic terns Sterna paradisaea nested on about 75 islands in the Gulf of Maine in 1885, but persecution reduced the number about 16 colonies by 1900. Following legal protection, tern number increased until about 1940, when approximately 8,000 pairs each of common and Arctic terns nested on approximately 25 islands. After that tern numbers declined in Maine as herring gull Larus argentatus and great black-backed gull Larus marinus populations increased. By 1977, the Arctic tern population had declined to 3,146 pairs on 9 islands and common terns 2,095 pairs on 24 islands. Roseate terns showed a similar pattern, as numbers declined from about 275 pairs in 1931 to just 80 pairs in 1977.
On Eastern Egg Rock, a 2.9 ha, treeless island located 9 km from the shore, gull control began in 1974, at which point the island was dominated by about 200 pairs of great black-backed gulls. Each year from 1978 to 1981, 28 tern decoys, some with a head extended posture and others with a short-necked, incubating posture, were placed in suitable habitat. In 1978 and 1979, Arctic tern colony sounds were broadcast from speakers located near the decoys when terns were sighted (and in 1980 and 1981 from dawn to dusk). Both Arctic and common terns began landing with decoys soon after the attraction program started. During 1978 and 1979, terns loafed with the decoys and often interacted with them, offering fish to the models, making scrapes and parading with nesting material. During these years the terns chased off gulls and humans which approached the vicinity. By July 1980, there were 12 Arctic tern nests and 20 common tern nests, all clustered among the decoys, with the sound speaker in the middle and by the end of the season the colony had grown to 80 pairs of terns. By 1996, Eastern Egg Rock was the largest common tern colony in Maine with 1,374 pairs and roseate terns had increased to at least 126 pairs (78% of all roseate terns nesting in Maine). The Arctic tern colony on Eastern Egg Rock was small at this time, being focussed on Seal Island.
Seal Island National Wildlife Refuge is a 40ha treeless island 29 km from the mainland. Gulls completely excluded terns from Seal Island by the mid-1950s and so gull control began in 1984. Each year from 1985-1989, 50 Arctic tern decoys were set in suitable habitat and a tape recording of Arctic tern courtship calls, was played from dawn to dusk on most days. Arctic terns began landing within several days of placement of decoys, sitting among the decoys or attempting to feed them small fish. Low levels of tern activity were observed from 1985-1988. In 1989, tern numbers increased late in the season forming a colony of 16 pairs of Arctic terns and 1 pair of common terns. Late nesting suggests that the birds had failed elsewhere and made a second nesting attempt at Seal Island. By 1996, there were 956 pairs of Arctic terns and 780 pairs of common terns at the colony. A few pairs of roseate terns nested at Seal Island in 1991 and 1995 but remained a rare breeder.
Kress concluded that factors associated with recolonization included:
Kotliar & Burger (1984) studied a sand and shell island in New Jersey, USA, finding 81% of 821 least tern Sterna antillarum landings between 19th and 25th May 1983 were in a 100 m2 plot with tern decoys and only 19% in a control plot without decoys. The first three nests established were within 3m of a decoy and none of the first 28 nests was in the control plot. Burger (1988) tested the role of decoy numbers, spacing and apparent mating status on social attraction of least terns and found birds were more attracted to larger groups of decoys (groups of 20 preferred to groups of 10); to wider-spaced tern decoys (1.5 m apart rather than 0.5 m apart); to solitary rather than paired decoys; and to plots containing decoys both singly and in pairs rather than singly alone.
Roby et al. (2002) studied two small islands in the Columbia River Estuary, Oregon, USA, where a Caspian tern Hydroprogne caspia colony of c.8,900 pairs) was relocated from Rice Island to East Sand Island between 1999 and 2001 to reduce conflict with fishermen. The project created and maintained 1.5-3.0 ha suitable nesting habitat and deployed 253-415 decoys each year, with between two and four audio systems, broadcasting the sounds of a Caspian tern colony on East Sand Island, while vegetation was encouraged on Rice Island by fencing and planting wheat. Caspian terns shift breeding colony sites frequently in response to changing habitats and breeding success, and are a generalist forager, preying on the most available forage fish near the colony, so the project was successful in reducing conflict with fishermen.
Jeffries & Brunton (2001) found that New Zealand fairy terns Sternula nereis davisae were significantly more likely to land in experimental plots with tern decoy models compared to control plots, with 80% of all landing episodes in experimental plots with decoys. By contrast, they found that New Zealand fairy terns were no more likely to land in experimental plots when a tape of fairy tern calls was played, compared to days when calls were not played.
Freare et. al. (2015) found that a combination of decoys and sound lures was most effective at attracting sooty terns Onychoprion fuscatus to previously occupied sites in the Seychelles restored by habitat management. Three dimensional decoys were more effective than two dimensional ones and decoys which were much larger than actual sooty terns were more effective than decoys which were closer to life size. Sooty terns spent more time flying over experimental plots where calls were being broadcast and had a significant preference for landing in plots with both three-dimensional models and sound. A breeding colony was not re-established however, possibly as a result of predation from common moorhen Gallinula chloropus and common myna Acridotheres tristis.
- Presence and number of surviving birds with a memory of nesting at the restoration site.
- A source of potential breeders with a history of nesting nearby.
- Expanding regional populations producing a supply of prospecting young birds.
- Disturbance at neighbouring colonies that result in poor productivity, encouraging birds to search for alternate nesting places.
Kotliar & Burger (1984) studied a sand and shell island in New Jersey, USA, finding 81% of 821 least tern Sterna antillarum landings between 19th and 25th May 1983 were in a 100 m2 plot with tern decoys and only 19% in a control plot without decoys. The first three nests established were within 3m of a decoy and none of the first 28 nests was in the control plot. Burger (1988) tested the role of decoy numbers, spacing and apparent mating status on social attraction of least terns and found birds were more attracted to larger groups of decoys (groups of 20 preferred to groups of 10); to wider-spaced tern decoys (1.5 m apart rather than 0.5 m apart); to solitary rather than paired decoys; and to plots containing decoys both singly and in pairs rather than singly alone.
Roby et al. (2002) studied two small islands in the Columbia River Estuary, Oregon, USA, where a Caspian tern Hydroprogne caspia colony of c.8,900 pairs) was relocated from Rice Island to East Sand Island between 1999 and 2001 to reduce conflict with fishermen. The project created and maintained 1.5-3.0 ha suitable nesting habitat and deployed 253-415 decoys each year, with between two and four audio systems, broadcasting the sounds of a Caspian tern colony on East Sand Island, while vegetation was encouraged on Rice Island by fencing and planting wheat. Caspian terns shift breeding colony sites frequently in response to changing habitats and breeding success, and are a generalist forager, preying on the most available forage fish near the colony, so the project was successful in reducing conflict with fishermen.
Jeffries & Brunton (2001) found that New Zealand fairy terns Sternula nereis davisae were significantly more likely to land in experimental plots with tern decoy models compared to control plots, with 80% of all landing episodes in experimental plots with decoys. By contrast, they found that New Zealand fairy terns were no more likely to land in experimental plots when a tape of fairy tern calls was played, compared to days when calls were not played.
Freare et. al. (2015) found that a combination of decoys and sound lures was most effective at attracting sooty terns Onychoprion fuscatus to previously occupied sites in the Seychelles restored by habitat management. Three dimensional decoys were more effective than two dimensional ones and decoys which were much larger than actual sooty terns were more effective than decoys which were closer to life size. Sooty terns spent more time flying over experimental plots where calls were being broadcast and had a significant preference for landing in plots with both three-dimensional models and sound. A breeding colony was not re-established however, possibly as a result of predation from common moorhen Gallinula chloropus and common myna Acridotheres tristis.
Case Studies
Use of common and little tern decoys is relatively frequent in the UK, but detailed information about the way in which they are deployed, and observations of birds reactions is not always easy to find.
Blakeney Point, England: attempting to move a colony a short distance on an established site
In 2015, little tern decoys were used to encourage birds to nest higher up the beach after a change in beach profile left the colony of up to 90 pairs prone to flooding. No sound lures were used. The decoys were made from clay donated by a local pottery ‘Made in Cley’, fired and painted with acrylic paints. The estimated cost for clay and paint to produce 25 decays was about £35.
The decoys were placed in three areas, with the following results:
Site A: A relatively small area inside a new fence line; 10 decoys placed, and no birds nested. The rangers believe that the decoy pattern was too dense and discouraged furthers nests in this area.
Site B: Higher up the beach in the main colony; 10 decoys placed in a small area. Birds nested further down the beach, in traditional areas, away from the decoys.
Site C: A larger enclosed area of suitable habitat occasionally used by 1 to 3 late nesting pairs; 3 decoys placed. Ten pairs nested and fledged 12 chicks.
The conclusion drawn was that a relatively large area of suitable habitat is needed and it is best not to overcrowd it with decoys (see also Burger, 1988, above). The decoys only appeared to attract birds to the general area, and not to a specific site, so were thought unsuitable for moving nesting birds a short distance on an established site. Other factors may have influenced nesting decisions including changing vegetation and predation risk.
Use of common and little tern decoys is relatively frequent in the UK, but detailed information about the way in which they are deployed, and observations of birds reactions is not always easy to find.
Blakeney Point, England: attempting to move a colony a short distance on an established site
In 2015, little tern decoys were used to encourage birds to nest higher up the beach after a change in beach profile left the colony of up to 90 pairs prone to flooding. No sound lures were used. The decoys were made from clay donated by a local pottery ‘Made in Cley’, fired and painted with acrylic paints. The estimated cost for clay and paint to produce 25 decays was about £35.
The decoys were placed in three areas, with the following results:
Site A: A relatively small area inside a new fence line; 10 decoys placed, and no birds nested. The rangers believe that the decoy pattern was too dense and discouraged furthers nests in this area.
Site B: Higher up the beach in the main colony; 10 decoys placed in a small area. Birds nested further down the beach, in traditional areas, away from the decoys.
Site C: A larger enclosed area of suitable habitat occasionally used by 1 to 3 late nesting pairs; 3 decoys placed. Ten pairs nested and fledged 12 chicks.
The conclusion drawn was that a relatively large area of suitable habitat is needed and it is best not to overcrowd it with decoys (see also Burger, 1988, above). The decoys only appeared to attract birds to the general area, and not to a specific site, so were thought unsuitable for moving nesting birds a short distance on an established site. Other factors may have influenced nesting decisions including changing vegetation and predation risk.
Long Nanny, England: attempting to move a colony with vegetation management and decoys
The Long Nanny, Northumberland, UK, is a site of dynamic coastal change, especially during winter storms, occupying 7.5ha of sand beach, saltmarsh and dunes. The primary nesting area for terns is a low-lying sand spit at the north eastern end of the site which in recent years has eroded and now much of the spit is regularly covered by spring tides.
An area with a higher elevation reducing the likelihood of tidal inundation was rotovated in 2016 to attract terns. Six life-sized painted plaster little tern decoys and three slightly larger glazed ceramic decoys were placed in scrapes in the rotavated area and in an elevated area of the saltmarsh adjacent, and a recording of little tern calls was played in the decoy area from 0800hrs to 1000hrs and 1400hrs to 1600hrs daily between the 14thMay and the 2nd June.
The Long Nanny, Northumberland, UK, is a site of dynamic coastal change, especially during winter storms, occupying 7.5ha of sand beach, saltmarsh and dunes. The primary nesting area for terns is a low-lying sand spit at the north eastern end of the site which in recent years has eroded and now much of the spit is regularly covered by spring tides.
An area with a higher elevation reducing the likelihood of tidal inundation was rotovated in 2016 to attract terns. Six life-sized painted plaster little tern decoys and three slightly larger glazed ceramic decoys were placed in scrapes in the rotavated area and in an elevated area of the saltmarsh adjacent, and a recording of little tern calls was played in the decoy area from 0800hrs to 1000hrs and 1400hrs to 1600hrs daily between the 14thMay and the 2nd June.
Little terns were seen flying over, taking off or landing on the decoy area on seventeen occasions between 12th and 21st May, including one occasion when a tern was observed apparently calling to a decoy. Two empty scrapes were found in the rotavated area on the 7th May but they were shallow with plover footprints nearby so were almost certainly made by ringed plover. No little tern nesting attempts were recorded in the decoy area.
It may be that because the original habitat still appears suitable (until the spring tides) it is still more attractive to little terns.
It may be that because the original habitat still appears suitable (until the spring tides) it is still more attractive to little terns.
Figure 5. As little terns persisted in nesting in areas prone to flooding, the highly-interventionist measure of raising nests on fish crates continued in order to prevent the nests being lost (Olly Slessor)
Coquet Island, England: little tern decoys and lures in unsuitable habitat
Little tern decoys and a tape lure have been deployed on Coquet Island, Northumberland, UK for four seasons, without attracting birds from the nearby colonies at the Long Nanny or Lindisfarne. This is probably because the island lacks the low open shingle habitat with an open aspect that little terns prefer.
Little tern decoys and a tape lure have been deployed on Coquet Island, Northumberland, UK for four seasons, without attracting birds from the nearby colonies at the Long Nanny or Lindisfarne. This is probably because the island lacks the low open shingle habitat with an open aspect that little terns prefer.
Solent, England: common tern decoys on rafts at two contrasting sites
On the south coast of England common tern decoys were deployed on new tern rafts in two areas in 2017. At West Hayling, the rafts were occupied almost immediately, which was probably due to the pre-existing tern nesting habitat being dominated by gulls and the deployment of the rafts being timed to coincide with the terns arriving so that the earlier arriving gulls couldn’t settle on them. At North Solent National Reserve new rafts deployed at the same time were not used initially, probably as (1) there were areas of “natural” habitat which still had space when the terns returned (although prone to flooding due to erosion and sea level raise, proximity to predators etc.), (2) the raft locations were away from the primary colony areas and feeding zones, requiring a pioneer to commit to the rafts before others would follow and (3) the raft design might have been suboptimal, especially with regards to its size.
On the south coast of England common tern decoys were deployed on new tern rafts in two areas in 2017. At West Hayling, the rafts were occupied almost immediately, which was probably due to the pre-existing tern nesting habitat being dominated by gulls and the deployment of the rafts being timed to coincide with the terns arriving so that the earlier arriving gulls couldn’t settle on them. At North Solent National Reserve new rafts deployed at the same time were not used initially, probably as (1) there were areas of “natural” habitat which still had space when the terns returned (although prone to flooding due to erosion and sea level raise, proximity to predators etc.), (2) the raft locations were away from the primary colony areas and feeding zones, requiring a pioneer to commit to the rafts before others would follow and (3) the raft design might have been suboptimal, especially with regards to its size.
Figure 6. Roseate tern decoys on the Skerries, off Anglesey, UK in 2016, deployed on newly created terraces alongside nest boxes (Ian Sims; RSPB)
Skerries, Wales: roseate tern decoys and nest boxes
On the Skerries, Anglesey, a roseate tern terrace, nest boxes, and decoys were deployed in 2017. A tape lure was also deployed but failed within a couple of weeks. Despite the fact that no roseate terns nested on the terrace, one pair nested on the island in 2018 and two pairs in 2019 both in the vicinity of the terrace and decoys. It is important to note that there were up to three mixed pairs of common and roseate terns on the island prior the colonisation of “pure” pairs, which might have contributed to the attractiveness of the site to the new colonisers, along with the presence of suitable habitat and an established common tern colony.
On the Skerries, Anglesey, a roseate tern terrace, nest boxes, and decoys were deployed in 2017. A tape lure was also deployed but failed within a couple of weeks. Despite the fact that no roseate terns nested on the terrace, one pair nested on the island in 2018 and two pairs in 2019 both in the vicinity of the terrace and decoys. It is important to note that there were up to three mixed pairs of common and roseate terns on the island prior the colonisation of “pure” pairs, which might have contributed to the attractiveness of the site to the new colonisers, along with the presence of suitable habitat and an established common tern colony.
Relevant sections of Conservation Evidence
Action: Use decoys to attract birds to safe areas
Action: Use vocalisations to attract birds to safe areas
Action: Use decoys to attract birds to safe areas
Action: Use vocalisations to attract birds to safe areas
References
Arnold, J.M., Nisbet, I.C. and Veit, R. (2011), Assessing aural and visual cueing as tools for seabird management. The Journal of Wildlife Management, 75: 495-500. doi: 10.1002/jwmg.76
Blokpoel H., Tessier G.D. & Andress R.A. (1997) Successful restoration of the Ice Island common tern colony requires on-going control of ring-billed gulls. Colonial Waterbirds, 20, 98-101
Burger, J. (1988) Social Attraction in Nesting Least Terns: Effects of Numbers, Spacing, and Pair Bonds, The Condor, Volume 90, Issue 3, Pages 575–582, https://doi.org/10.2307/1368345
Feare C.J., French G.C.A., Nevill J.E.G., Pattison-Willits V.S., Wheeler V., Yates T.L., Hoareau C. & Prescott C.V. (2015) Attempted re-establishment of a sooty tern Onychoprion fuscatus breeding colony on Denis Island, Seychelles. Conservation Evidence, 12, 19-24
Jeffries D.S. & Brunton D.H. (2001) Attracting endangered species to 'safe' habitats: responses of fairy terns to decoys. Animal Conservation, 4, 301-305
Kotliar N.B. & Burger J. (1984) The use of decoys to attract least terns (Sterna antillarum) to abandoned colony sites in New Jersey. Colonial Waterbirds, 7, 134-138
Kress, S.W. (1983) The use of decoys, sound recordings, and gull control for re-establishing a tern colony in Maine. Colonial Waterbirds 6: 185–196.
Kress, S.W. 1997: Using animal behaviour for conservation: case studies in seabird restoration from the Maine coast, USA. Journal of the Yamashina Institute for Ornithology 29(1): 1–26.
Lampman K., Taylor M. & Blokpoel H. (1996) Caspian terns (Sterna caspia) breed successfully on a nesting raft. Colonial Waterbirds, 19, 135-138
Pynenburg, B.P., Moore, D.J. & James S. Quinn (2017) Efficacy of decoys and familiar versus unfamiliar playback calls in attracting Common Terns to a rehabilitated wetland on Lake Ontario. Aquatic Ecosystem Health & Management, 20:3, 285-294.
Roby D.D., Collis K., Lyons D.E., Craig D.P., Adkins J.Y. & Myers A.M. (2002) Effects of colony relocation on diet and productivity of Caspian terns. The Journal of Wildlife Management, 66, 662-67
Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.
Acknowledgements
Thanks to: Wez Smith (RSPB), Pete Jones (Cumbria Wildlife Trust) and Ron Thomas (RSPB volunteer), Chantal Macleod-Nolan (RSPB), Ian Sim (RSPB) and Paul Davis (RSPB/Essex Wildlife Trust)
Arnold, J.M., Nisbet, I.C. and Veit, R. (2011), Assessing aural and visual cueing as tools for seabird management. The Journal of Wildlife Management, 75: 495-500. doi: 10.1002/jwmg.76
Blokpoel H., Tessier G.D. & Andress R.A. (1997) Successful restoration of the Ice Island common tern colony requires on-going control of ring-billed gulls. Colonial Waterbirds, 20, 98-101
Burger, J. (1988) Social Attraction in Nesting Least Terns: Effects of Numbers, Spacing, and Pair Bonds, The Condor, Volume 90, Issue 3, Pages 575–582, https://doi.org/10.2307/1368345
Feare C.J., French G.C.A., Nevill J.E.G., Pattison-Willits V.S., Wheeler V., Yates T.L., Hoareau C. & Prescott C.V. (2015) Attempted re-establishment of a sooty tern Onychoprion fuscatus breeding colony on Denis Island, Seychelles. Conservation Evidence, 12, 19-24
Jeffries D.S. & Brunton D.H. (2001) Attracting endangered species to 'safe' habitats: responses of fairy terns to decoys. Animal Conservation, 4, 301-305
Kotliar N.B. & Burger J. (1984) The use of decoys to attract least terns (Sterna antillarum) to abandoned colony sites in New Jersey. Colonial Waterbirds, 7, 134-138
Kress, S.W. (1983) The use of decoys, sound recordings, and gull control for re-establishing a tern colony in Maine. Colonial Waterbirds 6: 185–196.
Kress, S.W. 1997: Using animal behaviour for conservation: case studies in seabird restoration from the Maine coast, USA. Journal of the Yamashina Institute for Ornithology 29(1): 1–26.
Lampman K., Taylor M. & Blokpoel H. (1996) Caspian terns (Sterna caspia) breed successfully on a nesting raft. Colonial Waterbirds, 19, 135-138
Pynenburg, B.P., Moore, D.J. & James S. Quinn (2017) Efficacy of decoys and familiar versus unfamiliar playback calls in attracting Common Terns to a rehabilitated wetland on Lake Ontario. Aquatic Ecosystem Health & Management, 20:3, 285-294.
Roby D.D., Collis K., Lyons D.E., Craig D.P., Adkins J.Y. & Myers A.M. (2002) Effects of colony relocation on diet and productivity of Caspian terns. The Journal of Wildlife Management, 66, 662-67
Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.
Acknowledgements
Thanks to: Wez Smith (RSPB), Pete Jones (Cumbria Wildlife Trust) and Ron Thomas (RSPB volunteer), Chantal Macleod-Nolan (RSPB), Ian Sim (RSPB) and Paul Davis (RSPB/Essex Wildlife Trust)
Appendix 1. How to make a decoy mould for plaster tern decoys
by Wez Smith, RSPB Sites Manager, Langstone and Chichester Harbour.
1) Buy some standard air-drying clay and make a single tern decoy, this is going to be the basis for your mould. Let it dry out so that it’s completely set.
by Wez Smith, RSPB Sites Manager, Langstone and Chichester Harbour.
1) Buy some standard air-drying clay and make a single tern decoy, this is going to be the basis for your mould. Let it dry out so that it’s completely set.
2) Make a small box using foam card, or anything else generally waterproof that won’t buckle under high heat. This is to make your mould in. Put the original decoy in it and stick in a few cocktail sticks just to show where the centre line is (as you’ll need to cut down it later).
3) Melt some vinyl rubber in a big saucepan. It is also known as ‘vinamold’ (you can buy it here: http://www.maragon.co.uk/arts-and-crafts.html). This is what your mould is going to be made from. Once it has melted into a liquid form, pour it slowly all over the decoy and fill up the box to create a rectangular mould. Leave it to cool for at least 24 hours.
4) Once cool, cut the block in half and open it carefully. You should be left with a mould something like this:
5) Now it’s the easy bit. To make as many copies as you want, all you need to do is place the two halves back together, wrap the whole thing in clingfilm (to make it waterproof) and then pour outdoor plaster into it (we use Cassini’s, available from the same link as the vinyl rubber above). Once it is dry, you can open it, take out the decoy tern and repeat until you have the number you are after.
5) Now it’s the easy bit. To make as many copies as you want, all you need to do is place the two halves back together, wrap the whole thing in clingfilm (to make it waterproof) and then pour outdoor plaster into it (we use Cassini’s, available from the same link as the vinyl rubber above). Once it is dry, you can open it, take out the decoy tern and repeat until you have the number you are after.
6) You then just have to paint them in the appropriate colours.
Appendix 2. Plastic tern decoy making methodology
by Pete Jones of Cumbria Wildlife Trust
For the 2016 bird breeding season Cumbria Wildlife Trust created some tern decoys using rotocast plastic. The use of decoys is well documented and had been successful on the tern breeding colony at Foulney Island near Barrow in Furness. However, the traditional method of making terns using clay or paper-mache has drawbacks that rotocast plastic solves. Clay and paper-mache models take a long time to make and the models never last that long (in some cases only one season before more need to be made). Once a rotocasting setup is established, decoys can be produced much quicker using the new method (one person can produce around 5 or 6 an hour), and they will last much longer out in the elements, eliminating the need to make a new batch every year.
The following methodology will go through how to make a master model, create a mould and cast plastic decoys.
by Pete Jones of Cumbria Wildlife Trust
For the 2016 bird breeding season Cumbria Wildlife Trust created some tern decoys using rotocast plastic. The use of decoys is well documented and had been successful on the tern breeding colony at Foulney Island near Barrow in Furness. However, the traditional method of making terns using clay or paper-mache has drawbacks that rotocast plastic solves. Clay and paper-mache models take a long time to make and the models never last that long (in some cases only one season before more need to be made). Once a rotocasting setup is established, decoys can be produced much quicker using the new method (one person can produce around 5 or 6 an hour), and they will last much longer out in the elements, eliminating the need to make a new batch every year.
The following methodology will go through how to make a master model, create a mould and cast plastic decoys.
1. Making the master
To produce a mould, you will need a master model to get a mould from. You will be using silicon for the mould (as will be explained later) and this does impose some restrictions on the master model. Most silicons will not cure properly if in contact with anything containing sulphur, so our master has to be sulphur free. Most regular plasticines contain small amounts of sulphur and so are not good for this purpose. We used DAS modelling clay. This clay is air drying and can be found in most craft supply shops. Sulphur free plasticine can be found but is a little specialist and can be expensive.
To produce a mould, you will need a master model to get a mould from. You will be using silicon for the mould (as will be explained later) and this does impose some restrictions on the master model. Most silicons will not cure properly if in contact with anything containing sulphur, so our master has to be sulphur free. Most regular plasticines contain small amounts of sulphur and so are not good for this purpose. We used DAS modelling clay. This clay is air drying and can be found in most craft supply shops. Sulphur free plasticine can be found but is a little specialist and can be expensive.
- The first step in the process is to sculpt a master model. Use photographs and books as reference material (I found photos of the birds in the hand, whilst being ringed, were particularly useful to gauge size).
- Use wooden sticks or metal wire to sculpt the clay around. This skeleton or armature will strengthen the model as it dries.
- Mount the master model on a piece of clay to act as a base. This will create the fill hole in the silicon mould.
- Try to get the finish on the master as close to perfect as possible. The mould will take on all surface irregularities so time spent getting the surface relatively smooth now will make for better decoys.
- If using DAS clay, the master model must be left to dry. Depending on the decoy being produced this can take several days.
- Once dry the master can have a spray varnish applied to seal it. This is not essential but will allow the master to be used for multiple moulds if required. Water in the liquid silicon can be absorbed by the dry clay causing the master to become brittle and easily damaged when removing from the mould. Sealing the master solves this problem. An acrylic based clear spray is the best – I found one in an auto-parts store for use when re-spraying cars. However, if you can find a matt varnish that would be better as it gives the finished decoys a matt finish, making them easier to paint.
2. Making the dump mould
The type of mould used in this process is called a dump mould. This is the simplest form of mould to make and is ideal for this application. It is termed a dump mould as the mould material is ‘dumped’ in the mould in one go. To make the mould you will need to build an open box around the master.
The base and walls of the mould can be made of anything like heavy card or thin, rigid plastic. I used foamcore (sometimes called mounting board in craft supply shops). This is a layer of thin, rigid foam in between two layers of tough paper. It is rigid, easy to cut, and fairly waterproof.
- Secure the master model to a sheet of foamcore. This can be done with hot glue or other non-sulphur glue.
- Cut out and glue down foamcore to create an open box around the master. As this will be the outside shape of the silicon mould you want to limit ‘dead’ space around the master. This will just become solid silicon with no mould space in it. It will make the mould heavier than it needs to be and is a waste of silicon. There only needs to be a gap of around 1cm between the outside of the master and the mould wall.
- Once the mould walls are built, the volume needs to be worked out. The easiest way to do this is to fill the mould (with the master in place) with sand or some other dry pourable material. Fill the mould with the sand and then pour it into a measuring jug to get the volume of the mould. This is how much silicon will be needed.
The silicon that we have used for our moulds is Smooth On Mold Max 14 NV. This is a tin-cure silicon with a Shore A hardness of 14. The NV stands for No Vacuum, meaning that vacuum degassing is not needed. It is an A:B mix silicon which has a mix ratio of 100A:10B by weight. A set of scales is needed to measure out what you need.
- Before measuring out, mix part A on its own to stop problems due to settling in transit.
- When you have estimated the volume of silicon needed you can convert that to weight using the data sheets that come with the silicon. Measure out the two parts into individual containers. Plastic tubs or cups are the easiest things to use. Containers can be cleaned and reused but take a lot of cleaning!
- Once combined the Mold Max 14 NV has a pot life of 40 minutes. This is plenty of time to mix and pour. Mix the two parts thoroughly for around 3 minutes.
- When mixed, start pouring the liquid silicon into the mould at the lowest point. This should eliminate trapped air in the mould. Pour steadily from a height (this reduces the amount of trapped air in the mix) until the master is covered. Pour around 1-1.5 cm depth over the highest point of the master.
- Once poured, leave the mould somewhere undisturbed until cured.
- When cured the mould walls can be ripped away from the mould, freeing the silicon mould with the master still inside.
- The master will now need to be removed from the mould. Turn the mould over so the bottom of the master base is showing. Using a sharp craft knife cut a zigzag line from the master base to the end of where the tail is. Then cut another zigzag line from the master base to the point of the beak. The cut line should only be zigzag shaped at the surface. Once the surface has been cut like this the rest of the cut line should be as straight as possible. The zigzag line allows for accurate registering, where the mould can be closed precisely without movement between the cut edges.
- Remove the master from the mould.
- Clean up any clay from inside the model and wash with water. Dry thoroughly.
- The mould is complete and ready to cast from.
3. Rotocasting
To create plastic decoys using the mould we will need to fill it with a liquid that hardens. Filling the mould cavity full of liquid plastic is an option but is wasteful of plastic. Rotocasting is the process of coating the inside of the mould with a thin layer of plastic. A small amount of plastic is added whilst liquid and the mould is sealed and rotated to evenly coat the inside of the mould. This rotation continues whilst the plastic cures. Once cured this plastic ‘shell’ can be removed. The decoy is still strong and durable but much less plastic is used.
4. Preparing the mould
The mould needs to be secured together so that liquid poured into it does not escape as it is curing. The best way of doing this is to get spare bits of foamcore roughly the shape of the sides of the mould and use sticky tape (either duct tape or strong masking tape) to wrap tightly around the mould and foamcore to close it up.
Once secured, a plug can be found for the opening. This plug need to fit the hole tightly so that no liquid escapes (it is not a big problem if a small amount escapes during the casting process). Once filled, the plug will need to be secured somehow. We used strong masking tape to do this.
To create plastic decoys using the mould we will need to fill it with a liquid that hardens. Filling the mould cavity full of liquid plastic is an option but is wasteful of plastic. Rotocasting is the process of coating the inside of the mould with a thin layer of plastic. A small amount of plastic is added whilst liquid and the mould is sealed and rotated to evenly coat the inside of the mould. This rotation continues whilst the plastic cures. Once cured this plastic ‘shell’ can be removed. The decoy is still strong and durable but much less plastic is used.
4. Preparing the mould
The mould needs to be secured together so that liquid poured into it does not escape as it is curing. The best way of doing this is to get spare bits of foamcore roughly the shape of the sides of the mould and use sticky tape (either duct tape or strong masking tape) to wrap tightly around the mould and foamcore to close it up.
Once secured, a plug can be found for the opening. This plug need to fit the hole tightly so that no liquid escapes (it is not a big problem if a small amount escapes during the casting process). Once filled, the plug will need to be secured somehow. We used strong masking tape to do this.
The urethane plastic that we used for our decoys was Smooth On Smooth-Cast 65D. This is a semi-rigid urethane which is able to stand up to rough treatment without breaking. It has a Shore A hardness of 65 which is quite rigid without being brittle. It is an A:B mix urethane which has a mix ration of 1:1 by volume.
To work out the volume of plastic needed we used trial and error. We started with a rough guess and after one cast realised that we could use less. The next few casts had reduced amounts of urethane until we were happy with the thickness of the shell.
Before rotocasting, shake the containers of part A and B to ensure mixing of any settling. Then measure out the two parts of the urethane into individual cups. We use plastic drink cups with the volume drawn on the outside of the cup in marker pen.
Have a stop-watch at hand to time the next few steps.
Once measured, start the stop-watch and the two parts can then be combined and mixed. The pot life of Smooth-Cast 65D is 2 minutes 30 seconds so fast working here is essential. Mix for around 30 seconds and ensure that the two parts are completely combined. When liquid, the urethane is transparent but cures white.
Once combined pour the urethane into the opening of the mould, then quickly put the plug in and secure with tape to ensure as good a seal as possible.
To work out the volume of plastic needed we used trial and error. We started with a rough guess and after one cast realised that we could use less. The next few casts had reduced amounts of urethane until we were happy with the thickness of the shell.
Before rotocasting, shake the containers of part A and B to ensure mixing of any settling. Then measure out the two parts of the urethane into individual cups. We use plastic drink cups with the volume drawn on the outside of the cup in marker pen.
Have a stop-watch at hand to time the next few steps.
Once measured, start the stop-watch and the two parts can then be combined and mixed. The pot life of Smooth-Cast 65D is 2 minutes 30 seconds so fast working here is essential. Mix for around 30 seconds and ensure that the two parts are completely combined. When liquid, the urethane is transparent but cures white.
Once combined pour the urethane into the opening of the mould, then quickly put the plug in and secure with tape to ensure as good a seal as possible.
Immediately pick up the mould and start to rotate it at about the rate of 1 rotation every second. Randomly rotate the mould side to side, front to back, upside down, etc. to ensure the urethane covers the entire of the inside of the mould. Keep this rotating motion going even when you stop feeling the liquid moving about in the mould.
The cure time for Smooth-Cast 65D is around 15 minutes. However you do not need to rotate the mould for all of this time. Due to the gradual cure profile, after about 8 minutes the plastic will no longer flow and so the rotating can stop. This can be double checked against the residual urethane in the mixing cup. You will see this slowly turn white and start to cure. After 8 minutes, check the mixing cup. If confident that the plastic would not flow then place the mould, master base side down, on a flat surface and wait for the rest of the cure time to elapse. If you have two moulds, the next can be prepped, filled and rotated, whilst the first cures. This doubles the efficiency of production.
Once the cure time has elapsed, the decoy can be demoulded. Carefully remove the tape and strengthening bits of foamcore from the mould and open the mould to remove the decoy.
Once demoulded, leave to completely harden and then trim off any excess plastic around the seam lines (known as flashing).
The cure time for Smooth-Cast 65D is around 15 minutes. However you do not need to rotate the mould for all of this time. Due to the gradual cure profile, after about 8 minutes the plastic will no longer flow and so the rotating can stop. This can be double checked against the residual urethane in the mixing cup. You will see this slowly turn white and start to cure. After 8 minutes, check the mixing cup. If confident that the plastic would not flow then place the mould, master base side down, on a flat surface and wait for the rest of the cure time to elapse. If you have two moulds, the next can be prepped, filled and rotated, whilst the first cures. This doubles the efficiency of production.
Once the cure time has elapsed, the decoy can be demoulded. Carefully remove the tape and strengthening bits of foamcore from the mould and open the mould to remove the decoy.
Once demoulded, leave to completely harden and then trim off any excess plastic around the seam lines (known as flashing).
5. Painting
The decoys can now be painted with acrylic paints. If the master was varnished the decoys may need light sanding to roughen the surface to allow the paint to adhere. Once painted, use an acrylic spray varnish to give them protection against the weather. Most auto spray varnishes also have some level of UV protection in them which again increases the protection afforded to the decoys.
Glossary
Rotocast – A method of casting that creates a model shell rather than a solid model.
Master Model – the sculpted model that is used to make a mould from.
Silicon – A material that is ideal for making moulds from.
Urethane – A plastic that can be used for casting purposes.
DAS clay – A natural, air drying clay that can be sculpted.
Armature – A structure inside a clay or plasticine sculpt that gives it strength whilst it dries.
Dump mould – A simple type of mould where the mould material is ‘dumped’ over the master model.
Foamcore – A layer of rigid foam in between two sheets of thick paper. Also called Mounting Board.
Mould walls – Rigid, water resistant walls making an open box, that the liquid mould material can be poured into.
Appendix 3. RSPB Sound Lures
As with decoys, sound lures are a very niche item and it can be hard to find a supplier. It may be possible to create lures using readily available units or using ready-made electronic components.
You will need:
As with decoys, sound lures are a very niche item and it can be hard to find a supplier. It may be possible to create lures using readily available units or using ready-made electronic components.
You will need:
- Speaker (consider how loud this needs to be for your site)
- Sound player (MP3, CD, tape)
- Timer or control
- Power source – internal rechargeable batteries/external battery sources
A standard RSPB-made lure in a waterproof box, used at little tern colonies e.g. Hodbarrow and potential sites e.g. Wallasea, Essex. The lure includes a timer, microprocessor and a shop-bought MP3 player.
A lure kit made by Ron Thomas (Ron Thomas)
How to make a lure kit
by Ron Thomas, Volunteer at RSPB Dee Estuary
The aim of building a lure kit is to keep it simple and low cost, but you will need to test its effectiveness in an outdoor situation. Things to obtain/consider:
1) You will need to be able to set a timer so that the sound can be turned on/off for day/night use or any other sequencing that may be required.
2) I recommend having two mobility scooter batteries. These last 2–3 days before they need a recharge. Having two means you can have one in use while the other is on charge.
3) You’ll need a small amplifier. You can buy these from electrical shops for around £25
4) You’ll also need an MP3 player, which you should be able to buy for about £8.
5) A suitable speaker is needed – we managed to buy two for £3 from a local charity shop, so it’s worth shopping around.
6) Voltage regulators will be needed if different parts of the set up need different voltages (for example the amplifier requires 9v and the MP3 player needs 3v). Smaller regulators are best to reduce the bulk of the kit.
7) A housing is needed for the kit e.g. an IP65 external mains distribution box. This will contain all the kit, minus the speaker. Such boxes are available for less than £20.
8) A tape recording of little tern display calls is needed and copyright needs to be considered.
by Ron Thomas, Volunteer at RSPB Dee Estuary
The aim of building a lure kit is to keep it simple and low cost, but you will need to test its effectiveness in an outdoor situation. Things to obtain/consider:
1) You will need to be able to set a timer so that the sound can be turned on/off for day/night use or any other sequencing that may be required.
2) I recommend having two mobility scooter batteries. These last 2–3 days before they need a recharge. Having two means you can have one in use while the other is on charge.
3) You’ll need a small amplifier. You can buy these from electrical shops for around £25
4) You’ll also need an MP3 player, which you should be able to buy for about £8.
5) A suitable speaker is needed – we managed to buy two for £3 from a local charity shop, so it’s worth shopping around.
6) Voltage regulators will be needed if different parts of the set up need different voltages (for example the amplifier requires 9v and the MP3 player needs 3v). Smaller regulators are best to reduce the bulk of the kit.
7) A housing is needed for the kit e.g. an IP65 external mains distribution box. This will contain all the kit, minus the speaker. Such boxes are available for less than £20.
8) A tape recording of little tern display calls is needed and copyright needs to be considered.