Citation: Babcock and Booth (2020) Roseate Tern Terraces and Nest Boxes. 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) Roseate Tern Terraces and Nest Boxes. Tern Conservation Best Practice. |
Key Messages
- Roseate terns, unlike other UK tern species, often choose nesting sites under overhanging vegetation or in burrows created by other species.
- Nest boxes provide a suitable artificial equivalent and are readily adopted, providing shelter from the weather and protection from predators.
- Nest boxes positioned in clusters on terraces near common tern colonies, in areas of low disturbance and good food supply appear to be the most attractive to roseate terns.
Information
While most UK tern species prefer to nest in open shingle areas with sparse vegetation, roseate terns Sterna dougallii often select sites on the ground under tall vegetation burrows or rock crevices. Roseate terns will readily use artificial nest boxes, and these are commonly distributed across artificially-created open areas known as terraces (probably because the earliest examples were often on a slope and comprised several levels). This combination of terraces and nest boxes appears to be attractive to roseate terns.
Terrace construction
The creation of enhancement of nesting areas for roseate terns will depend primarily on the characteristics of the site. Methods successfully used include building dry stone retaining walls (Coquet Island, Rockabill) and boards held in place with rebar/spikes (Rockabill, Great Gull Island).
Ongoing management and monitoring is easier if the tops of the terrace are covered to limit vegetation growth and/or, depending on the colony, burrowing species which might undermine the terrace. Tarpaulin, weed-supressing membranes, flagstones and interlocking plastic pavement slabs have all been used (note that it is advisable to have some drainage). A topping of gravel or shell substrate is suitable for construction of nest scrapes, and will also prevent eggs from rolling and raise them above any pooled water.
Terraces and nest boxes for roseate terns should where possible be adjacent to common tern Sterna hirundo nesting areas. This may cause some competition but the risk of this is outweighed by the benefit of more aggressive defence against predators, particularly large gulls (Rockabill, Coquet).
Roseate tern nest boxes should be densely distributed (around 30-40 cm apart) and facing the sea (Paul Morrison pers com.). At Lady’s Island Lake, Coquet Island and Rockabill boxes are collected after the breeding season for cleaning and storage and replaced in the same positions the next season, the box locations are mapped and/or marked with numbered weights over the winter. Vegetation management is usually required at the start of the season before replacing the boxes.
While most UK tern species prefer to nest in open shingle areas with sparse vegetation, roseate terns Sterna dougallii often select sites on the ground under tall vegetation burrows or rock crevices. Roseate terns will readily use artificial nest boxes, and these are commonly distributed across artificially-created open areas known as terraces (probably because the earliest examples were often on a slope and comprised several levels). This combination of terraces and nest boxes appears to be attractive to roseate terns.
Terrace construction
The creation of enhancement of nesting areas for roseate terns will depend primarily on the characteristics of the site. Methods successfully used include building dry stone retaining walls (Coquet Island, Rockabill) and boards held in place with rebar/spikes (Rockabill, Great Gull Island).
Ongoing management and monitoring is easier if the tops of the terrace are covered to limit vegetation growth and/or, depending on the colony, burrowing species which might undermine the terrace. Tarpaulin, weed-supressing membranes, flagstones and interlocking plastic pavement slabs have all been used (note that it is advisable to have some drainage). A topping of gravel or shell substrate is suitable for construction of nest scrapes, and will also prevent eggs from rolling and raise them above any pooled water.
Terraces and nest boxes for roseate terns should where possible be adjacent to common tern Sterna hirundo nesting areas. This may cause some competition but the risk of this is outweighed by the benefit of more aggressive defence against predators, particularly large gulls (Rockabill, Coquet).
Roseate tern nest boxes should be densely distributed (around 30-40 cm apart) and facing the sea (Paul Morrison pers com.). At Lady’s Island Lake, Coquet Island and Rockabill boxes are collected after the breeding season for cleaning and storage and replaced in the same positions the next season, the box locations are mapped and/or marked with numbered weights over the winter. Vegetation management is usually required at the start of the season before replacing the boxes.
Figure 1. Roseate tern terrace on Rockabill, with boxes close together and facing the sea; note the rock weights intended to hold the boxes in place in strong winds (RSPB).
Nest box design and positioning
Nest boxes were first used at US roseate tern colonies in the late 1980’s (Avery and del Nevo, 1991) before being adopted by Rockabill and then Coquet Island.
The first boxes used on Coquet Island were made of plywood, approximately 45 cm by 30 cm and 15 cm high, with a full height 15 cm wide door and either a flat or sloping roofed design (see Morrison & Gurney, 2007). The exact design is considered less important than the positioning near common terns, the clustering of boxes, lack of disturbance and availability of food.
Most boxes are made of plywood or marine ply, which is relatively light but does deteriorate with time in a marine environment. At Blue Circle Island, Larne Lough, Northern Ireland concrete boxes have been used (Figure 4), which are more durable but heavy to move. Three-sided boxes are also used; although on Rockabill it was found that chicks tend to leave these more quickly than more enclosed boxes (Newton & Glenister, 2008). Boxes usually have an open bottom, but boxes with floors have been used on bare rock on Dalkey Island (Figure 5) where such boxes are used a gravel or shell substrate should be provided in the box.
The association of roseate terns with common terns is thought to confer an advantage in terms of defending the colony, and perhaps may also act as an indicator of good habitat or foraging, so proximity to common terns may have a positive influence the colonisation of roseate tern boxes. However, on Falkner Island, Connecticut, USA, competition from common terns was considered a potential contributor to a decline in roseate tern pairs between 2008 and 2016. Another form of interspecific interaction was identified by Burke et. al. (2016) who found several instances of interspecies fostering between common and roseate terns where they breed in close proximity on Rockabill.
Published Research
Spendelow (1982) found that roseate terns on Falkner Island, CT, USA, had greater reproductive success when using nest sites modified to provide access to vegetated areas and additional shelter than when using unmodified sites.
Morrison & Gurney (2007) recorded changes in management and roseate tern numbers on Coquet Island, Northumberland, UK. Following the creation of a terrace and an increase in the number of nest boxes the number of roseate tern breeding pairs increased from 34 in 2000 to 94 in 2006, however it should be noted that this was set against a trend of population increase and cannot be directly attributed to these interventions. The effect on productivity is unknown as chicks would previously hide in long vegetation and so figures prior to introduction of the boxes are less reliable and should be considered minimum counts, however the development of the terrace and introduction of nest boxes also made monitoring far easier.
Spendelow (1982) found that roseate terns on Falkner Island, CT, USA, had greater reproductive success when using nest sites modified to provide access to vegetated areas and additional shelter than when using unmodified sites.
Morrison & Gurney (2007) recorded changes in management and roseate tern numbers on Coquet Island, Northumberland, UK. Following the creation of a terrace and an increase in the number of nest boxes the number of roseate tern breeding pairs increased from 34 in 2000 to 94 in 2006, however it should be noted that this was set against a trend of population increase and cannot be directly attributed to these interventions. The effect on productivity is unknown as chicks would previously hide in long vegetation and so figures prior to introduction of the boxes are less reliable and should be considered minimum counts, however the development of the terrace and introduction of nest boxes also made monitoring far easier.
Case Studies
Rockabill
The Rockabill Tern Project, a joint project between BirdWatch Ireland and the National Parks & Wildlife Service has been running since 1989 when there were 152 pairs of roseate terns on the island. At the time of writing around 900 nest boxes are deployed each year with a 90-95% occupancy rate. Roseate terns nesting in boxes on Rockabill study plots have consistently higher productivity than those that nest in the open (Figure 7) suggesting that boxes do confer an advantage.
Rockabill
The Rockabill Tern Project, a joint project between BirdWatch Ireland and the National Parks & Wildlife Service has been running since 1989 when there were 152 pairs of roseate terns on the island. At the time of writing around 900 nest boxes are deployed each year with a 90-95% occupancy rate. Roseate terns nesting in boxes on Rockabill study plots have consistently higher productivity than those that nest in the open (Figure 7) suggesting that boxes do confer an advantage.
Figure 6. Nest Boxes on Rockabill (Brian Burke)
Figure 7. Roseate tern productivity in Rockabill study areas (Birdwatch Ireland)
Coquet Island: roseate tern terrace and nest boxes
In 2000, following a visit to Rockabill, the number of roseate tern nest boxes on Coquet Island, Northumberland, was increased and a terrace was constructed, surfaced with flagstones to prevent undermining by puffins Fratercula arctica, and topped with fine shingle. In 2000, 25 nest boxes were deployed, by 2006 this was 200, and over 300 were put out in 2020 ensuring that there are always significantly more boxes available than the number of breeding pairs. Since 2003 all the roseate terns on the island have used nest boxes the majority for nesting and the remainder as chick shelters.
In 2018, there were 4 nest box variations in use on Coquet Island: the original square design and the second rectangular design made of plywood or marine ply (see Figure 2), plus two new box types. The new boxes were the same rectangular shape, but one made of recycled plastic and one of thicker, pale coloured compressed wood. A comparison of the relative occupancy rates of the four types suggested that the new recycled plastic boxes had the highest occupancy rate and the new compressed wood the lowest occupancy rate, however this was not a scientific study and it may be that box location was more important than design (Kinchin-Smith, Morrison & Redfern, 2019). It had been suggested that the dark colour of the recycled plastic boxes might mean that they got warmer than light-coloured boxes, but the boxes are quickly covered in tern guano in either case.
In 2000, following a visit to Rockabill, the number of roseate tern nest boxes on Coquet Island, Northumberland, was increased and a terrace was constructed, surfaced with flagstones to prevent undermining by puffins Fratercula arctica, and topped with fine shingle. In 2000, 25 nest boxes were deployed, by 2006 this was 200, and over 300 were put out in 2020 ensuring that there are always significantly more boxes available than the number of breeding pairs. Since 2003 all the roseate terns on the island have used nest boxes the majority for nesting and the remainder as chick shelters.
In 2018, there were 4 nest box variations in use on Coquet Island: the original square design and the second rectangular design made of plywood or marine ply (see Figure 2), plus two new box types. The new boxes were the same rectangular shape, but one made of recycled plastic and one of thicker, pale coloured compressed wood. A comparison of the relative occupancy rates of the four types suggested that the new recycled plastic boxes had the highest occupancy rate and the new compressed wood the lowest occupancy rate, however this was not a scientific study and it may be that box location was more important than design (Kinchin-Smith, Morrison & Redfern, 2019). It had been suggested that the dark colour of the recycled plastic boxes might mean that they got warmer than light-coloured boxes, but the boxes are quickly covered in tern guano in either case.
Isle of May: tern terrace creationThe Isle of May, in the Firth of Forth, Scotland, is owned and managed by Scottish Natural Heritage. It has supported varying numbers of breeding common, Arctic, roseate and Sandwich terns since the middle of the 19th century (Wanless, 1988). In 2015, a decision was taken to enhance nesting habitat for common and Arctic terns, with a longer-term goal of attracting roseate and Sandwich terns back to the island. Two areas were identified for the project, both traditional tern nesting areas with concrete foundations to facilitate construction and limit vegetation growth, located some distance from breeding gulls. The first, in the area known as the Beacon, also had the advantage of being largely undisturbed by visitors to the island, was constructed over the winter of 2015/16. The terraces were created by adding timber edging to the existing concrete bases and filling the them with sand and gravel from the island. Additional space was created with areas of membrane laid on the ground to limit vegetation growth and covered with sand and gravel. Nest boxes were also provided.
Figure 8. The Isle of May tern terraces at the Beacon in April 2016 (SNH). In subsequent years Coquet Island style sloping roof rectangular boxes were also used. After the 2019 breeding season the boxes were moved closer to the cliff edge which may be preferred by roseate terns, with more open common tern nesting areas behind.
During the 2016 breeding season the new terraces attracted Arctic and common terns, as well as the first Sandwich terns to breed on the Isle of May since 2008. Additional terraces were created from 2017 onwards in the area known as the Thistle Field, or Mouse House Field, using the same methods.
In subsequent years the number of Arctic and common tern breeding on the Island has increased, while Sandwich terns have nested in 3 of the 4 years after the creation of the terraces. In 2019, a single roseate tern settled, paired with a common tern and raised a chick. (David Steel, SNH, pers. com.)
Relevant sections of Conservation Evidence
Action: Provide artificial nesting sites for ground and tree-nesting seabirds
Action: Physically protect nests with individual exclosures/barriers or provide shelters for chicks of ground nesting seabirds
Action: Remove vegetation to create nesting areas
Action: Can nest protection increase predation of adults and chicks?
Action: Provide artificial nesting sites for ground and tree-nesting seabirds
Action: Physically protect nests with individual exclosures/barriers or provide shelters for chicks of ground nesting seabirds
Action: Remove vegetation to create nesting areas
Action: Can nest protection increase predation of adults and chicks?
References
Avery, M.I., & del Nevo, A.J. (1991). Action for roseate terns. RSPB Conservation Review, 5: 54– 59.
Burke, B., Power, A., Keogh, N. & Newton, S.F. (2016). Mother knows best? Interspecific fostering between Roseate Terns Sterna dougallii and Common Terns Sterna hirundo on Rockabill Island, County Dublin. Irish Birds. 10. 345-352.
Kinchin-Smith, D., Morrison, P. & Redfern, C. (2019) Coquet Island: Birds and Management for Wildlife [2018]. Northumbrian Naturalist, 86: 9 -16.
Morrison P. & Gurney M. (2007) Nest boxes for roseate terns Sterna dougallii on Coquet Island RSPB reserve, Northumberland, England. Conservation Evidence, 4, 1-3.
Newton, S.F. & Glenister, L.J. 2008. Rockabill Tern Manual (revised edition, November 2008). Unpublished BirdWatch Ireland Report, Newtownmountkennedy, Co. Wicklow
Spendelow, J. (1982). An Analysis of Temporal Variation in, and the Effects of Habitat Modification on, the Reproductive Success of Roseate Terns. Colonial Waterbirds, 5, 19-31. doi:10.2307/1521029
Wanless, S. (1988) The recolonisation of the Isle of May by Common and Arctic Terns. Scottish Birds 15: 1-8.
Acknowledgements
Thanks to Paul Morrison (RSPB Coquet Island), David Steel (Scottish Natural Heritage) and Steve Newton (Birdwatch Ireland) for assistance.
Avery, M.I., & del Nevo, A.J. (1991). Action for roseate terns. RSPB Conservation Review, 5: 54– 59.
Burke, B., Power, A., Keogh, N. & Newton, S.F. (2016). Mother knows best? Interspecific fostering between Roseate Terns Sterna dougallii and Common Terns Sterna hirundo on Rockabill Island, County Dublin. Irish Birds. 10. 345-352.
Kinchin-Smith, D., Morrison, P. & Redfern, C. (2019) Coquet Island: Birds and Management for Wildlife [2018]. Northumbrian Naturalist, 86: 9 -16.
Morrison P. & Gurney M. (2007) Nest boxes for roseate terns Sterna dougallii on Coquet Island RSPB reserve, Northumberland, England. Conservation Evidence, 4, 1-3.
Newton, S.F. & Glenister, L.J. 2008. Rockabill Tern Manual (revised edition, November 2008). Unpublished BirdWatch Ireland Report, Newtownmountkennedy, Co. Wicklow
Spendelow, J. (1982). An Analysis of Temporal Variation in, and the Effects of Habitat Modification on, the Reproductive Success of Roseate Terns. Colonial Waterbirds, 5, 19-31. doi:10.2307/1521029
Wanless, S. (1988) The recolonisation of the Isle of May by Common and Arctic Terns. Scottish Birds 15: 1-8.
Acknowledgements
Thanks to Paul Morrison (RSPB Coquet Island), David Steel (Scottish Natural Heritage) and Steve Newton (Birdwatch Ireland) for assistance.