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Little tern (Sternula albifrons)

The following has been adapted from original text by Georgina Pickerell in Seabird Populations of Britain and Ireland (with permission from A&C Black, London).

 

Little tern is the smallest species of tern breeding in the UK, nesting exclusively on the coast in well-camouflaged shallow scrapes on beaches, spits or inshore islets. They do not forage far from their breeding site, which dictates a necessity for breeding close to shallow, sheltered feeding areas where they can easily locate the variety of small fish and invertebrates that make up their diet. Colonies are found around much of the coastline, but the main concentration is in south and east England, where the species' preference for beaches also favoured by people makes it vulnerable to disturbance.

Conservation status

Little tern is currently identified as a conservation priority in the following:

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International importance

UK Population

Biogeographic Population

% World Population

1,900 AON*

9.7 (ssp. albifrons)

2.2

*AON = Apparently Occupied Nests

The UK population figure (rounded to the nearest hundred) was derived from data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E. (eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also the source of figures for the Biogeographic and World populations.

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UK population estimates and change 1969–2002 (census data)

Complete coverage of little tern colonies has been achieved in each national census. Site fidelity can be low from year to year, in response to predation, disturbance or habitat change. Thus, in order to gain an accurate national estimate of numbers, a simultaneous census was planned to cover all British colonies within a single year. During Seabird 2000, 93% of the population were counted in 2000, a marked improvement on the SCR Census when counts were spread over four years (13% counted in 1985, 21% in 1986, 63% in 1987 and 3% in 1988). There are no known colonies in Northern Ireland.

While the similarity in methods employed in both the SCR Census and Seabird 2000 ensures a valid comparison of their population estimates, the apparent population trend from a comparison of two such widely spaced surveys may be misleading. This is because the proportion of adult little terns choosing to nest in any one year fluctuates. Thus, more accurate trends are obtained from more frequently conducted counts (e.g. annually). Annual monitoring of little tern colonies has been conducted in Britain since 1969 with the colonies monitored currently holding about two-thirds of the national population.

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

UK Population estimate (AON*)

1,589

2,517

1,927

% change since previous census   

n/a

+58

-23

*AON = Apparently Occupied Nests

For census results for individual countries and Ireland, the Channel Islands and the Isle of Man see under relevant sections below.

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Distribution/abundance

The Seabird 2000 census provides the most comprehensive recent assessment of the distribution and abundance of breeding seabirds. Numbers of Little tern found in different regions, and a map showing the locations and size of colonies, is provided in the Seabird 2000 Little tern results page.

The locations sampled during the annual Seabird Monitoring Programme provide some information on distribution and are accessible via the Seabird Monitoring Programme online database.

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Annual abundance and productivity by geographical area

With reference to the regional accounts below please note the following:

Breeding abundance: graphs of abundance index with 95% confidence limits are only shown for a region where the trend produced has been deemed accurate (see methods of analysis). Where a trend was thought to be inaccurate, graphs of abundance at major colonies in a region may be shown instead, particularly if such colonies hold greater than 10% of the regional population, are monitored frequently and may thus help illustrate regional population fluctuations outwith national censuses. Occasionally, too few data have been collected regionally to produce either of these.

Productivity: graphs of productivity are only shown if analysis of breeding success data produced a significant result for regional and/or year effects (again see methods of analysis). If results were not significant, then a regional mean productivity value is given. However, on some occasions, too few data are available from which to provide a meaningful average. Furthermore, for 11 species where the quality of monitoring data available was considered high, population viability analysis was undertaken at the UK level and the results of this are also reported.

 

United Kingdom

Breeding abundance

little-tern-uk-ab.jpg

Figure 1. Trend in UK abundance index (solid line) of little tern 1986–2018 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis.

 

Figure 1 shows that little tern abundance generally declined after the late 1980s through to 2005 but then increased, showing signs of a partial recovery until 2012. In 2018, however, the index was 40% below the baseline, the lowest value ever recorded since 1986. Prior to the period shown above, little tern abundance had been in decline since the mid 1970s1, following increases during the early 1970s. The decline in numbers since 1986 has coincided with low productivity (see below), which is likely to have contributed to the decrease in abundance via low rates of recruitment into the breeding population.

 

Productivity

little-tern-uk-prod.jpg

Figure 2. Trend in UK productivity (no. of chicks fledged per pair) of little tern 1986–2018. Based on SMP data; view the methods of analysis.

 

The productivity of little terns has been relatively low throughout the recording period, although with a great deal of annual fluctuation since the lowest value was recorded in 1991. These low levels of productivity are insufficient to maintain the population by recruitment alone. Simple population models, incorporating annual productivity estimates with constant values for adult survival and age at first breeding, have predicted the observed decline in population size reasonably accurately2. Factors contributing to this low productivity include predation of chicks and eggs by foxes Vulpes Vulpes, kestrels Falco tinnunculus and corvids; nest loss due to bad weather; food shortage; and, most significantly, disturbance by humans. Most little terns nest along the east and south coasts of England, adjacent to some of the most densely populated areas of Britain, although many sites are now guarded in an attempt to limit disturbance. As little terns nest on low-lying ground close to the high water mark, their nests are vulnerable to erosion and tidal inundation, hence much work has been done on site management seeking to provide nesting areas safe from tidal inundation. Predictions of increased storminess and sea-level change under climate change scenarios may lead to increased prevalence of such events, though managed realignment3 of coastal defences may create new opportunities for nesting.

Analysis of the SMP dataset found mean little tern productivity to be relatively stable at around 0.51 chicks per nest per year between 1986 and 20084. The quality of the dataset indicated that a fall of 10% or less in productivity may not be detected, although a change in success of 25% or more would be detected with confidence. At this rate of productivity, using available life history information (population size, clutch size, age at first breeding and survival rates of different age classes) to parameterise population viability analysis, it is predicted that the population will decline by 41% over 25 years. If productivity were to increase to 0.70, population decline would be averted, and the population would stabilise.

Scotland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

308

373

331

% change since previous census   

n/a

+17

-11

*AON = Apparently Occupied Nests

 

Breeding abundance

little-tern-scotland-ab.jpg

Figure 3. Trend in abundance of little tern at two major Scottish colonies, 1986–2018.

 

The Scottish little tern population increased between Operation Seafarer and the Seabird Colony Register but had fallen again by the Seabird 2000 census. The few colonies surveyed each year do not, however, allow for an accurate population trend to be generated. Data shown above for two of the largest, and most frequently monitored, colonies indicate contrasting fortunes since Seabird 2000. Numbers at Sands of Forvie are similar to when monitoring began in 1986, whereas at Tiree Reef numbers have been more stable although may now be in decline, with low numbers recorded there in 2001, 2003, 2010, 2013, 2016 and also in 2018. At Sands of Forvie, an electric fence kept out the majority of ground predators, such as Foxes Vulpes vulpes and Badgers Meles meles, however, little terns failed to breed in 2016. The reasons for this are unclear, although poor spring weather and constant sandblow over the nesting habitat may have been a contributing factor5.

 

Productivity

little-tern-scotland-prod.jpg

Figure 4. Trend in productivity (no. of chicks fledged per pair) of little tern in Scotland, 1986–2018. Based on SMP data; view the methods of analysis.

 

Aside from obvious peaks in 1999, 2009 and 2014, little tern productivity at Scottish colonies tends to be rather low and in line with that recorded in England. This low productivity is due to a variety of factors such as predation, poor weather, disturbance and tidal inundation and may be too low to sustain the population without emigration from colonies from other countries. In 2014, little terns had a very productive breeding season while in 2015 productivity fell to the third lowest value recorded. Out of 13 colonies that reported productivity in 2015 only three bred successfully, producing a total of 15 chicks (cf 116 chicks in 2014). Since then, productivity has been fluctuating with only 3–5 colonies breeding in Scotland between 2016 and 20183,5. At The Reef RSPB reserve, productivity ranged from 0 to 0.25 between 2016 to 2018 with birds failing to breed in 2016. Here, heavy rain associated with Storm Hugo in mid-June 2018 saw most nests being flooded and failing at the egg/early chick phase with only 0.13 chicks fledged per pair. At Sands of Forvie in 2015 and 2017, all chicks failed at egg stage, due to a combination of poor weather and avian predation3,5. Productivity of little tern at Sands of Forvie improved again in 2018, when 0.50 chicks fledged.

 

England

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

1,247

2,087

1,521

% change since previous census   

n/a

+67

-27

*AON = Apparently Occupied Nests

 

Breeding abundance

little-tern-england-ab.jpg

Figure 5. Trend in abundance index (solid line) of little tern in England, 1986–2018 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis.

 

The trend shown for the UK closely matches that shown for England, where the majority of data have been collected over the years. The declining trend for little terns in England, visible since 1987, has been partially halted in recent years, no doubt through targeted management with many colonies now benefiting from some form of guarding (e.g. fencing, trapping, signage, surveillance and public relations). Prior to this, a large increase, of 67%, had occurred between Operation Seafarer and the Seabird Colony Register. Currently, the total population is below that recorded during Seabird 2000 (1,521 AON), with 981, 1,028 and 928 AON recorded in 2016, 2017 and 2018, respectively, although data are not submitted to the SMP for all colonies.

 

Productivity

little-tern-england-prod.jpg

Figure 6. Trend in productivity (no. of chicks fledged per pair) of little tern in England, 1986–2018. Based on SMP data; view the methods of analysis.

 

Productivity recorded at English colonies has also fluctuated markedly over the years but generally lies between 0.30–0.50 chicks fledged per pair per year; a fairly low value compared to e.g. Wales. As with Scotland, this level of productivity is probably insufficient to sustain population levels, and probably contributes to the decline in the abundance trend. Data from monitored colonies illustrate just how disastrous recent breeding seasons have been. In 2015, 45 colonies were visited but 19 of these held no breeding little terns and a further five failed completely. During April and May 2015, little terns encountered cool and windy weather as well as a lack of suitable small fish6. In common with other years, the reasons for failure were high tides, poor weather, disturbance; and predation of eggs, chicks and adults by mammals and other birds. Between 2016 to 2018, data were received from 32 colonies of which 7, 10 and 10 respectively did not hold any breeding little terns and a further 8, 6 and 6 colonies respectively failed completely.

 

Wales

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

28

55

75

% change since previous census   

n/a

+96

+36

*AON = Apparently Occupied Nests

 

Breeding abundance

little-tern-wales-ab.jpg

Figure 7. Abundance of little terns at Gronant, 1986–2018.

 

Although the population of little terns in Wales increased between each of the national censuses, the number of colonies since Seabird 2000 has declined to only two. At Gronant, numbers have fluctuated over the years, but the general trend is upward over time, possibly due to recent successful breeding seasons and subsequent increased recruitment into the colony. In recent years, the colony has consistently held four times the number of pairs it did in 1986. In 2015, numbers at Gronant were slightly below the 2014 figure at 136 AON, with one pair breeding at Point of Ayr (<4 km to the East). Numbers at Gronant decreased in 2015 to 123 AON, however, since then they have increased to 171 AON in 2018.

 

Productivity

At Gronant, an average of 1.00 chicks per pair were fledged each year between 1986 and 2018. Peaks in productivity were recorded in 1992, 2003, 2004 and 2010, all ranging between 1.78 and 1.92. In 2015, productivity was just above the average at 0.80, with 99 chicks fledged from 123 pairs. In addition, two chicks also fledged at Ary of Point, which was the first time for Wales in over 25 years that both sites bred successfully. The 2016 breeding season was an excellent, with Gronant producing a total of 170 chicks fledged from 141 pairs. This was followed by another productive season in 2017 when 202 chicks fledged from 161 pairs, taking productivity above 1.20 for the first time since 2010. In 2018, less chicks fledged and, therefore, productivity reduced to 1.12 chicks fledged per little tern pair.

 

Northern Ireland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

6

2

0

% change since previous census   

n/a

-67

-100

*AON = Apparently Occupied Nests

 

Breeding abundance

Six AON were recorded during Operation Seafarer, declining to two AON by the time of the Seabird Colony Register with none recorded during Seabird 2000. No little terns have been recorded breeding in Northern Ireland since then.

 

Productivity

No systematic data on the productivity of little terns in Northern Ireland were submitted to the SMP before the species ceased to breed in the country.

 

Republic of Ireland

Population estimates and change 1969–2018 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Republic of Ireland Census

(2015-18)

Population estimate (AON*)

309

280

206

388

% change since previous census   

n/a

-9

-26

+39

*AON = Apparently Occupied Nests

 

Breeding abundance

little-tern-ireland-ab.jpg

Figure 8. Abundance of little terns at Kilcoole, 1986–2018.

 

The little tern population in the Republic of Ireland declined 33% between the Operation Seafarer and Seabird 2000 censuses. While guarding colonies has succeeded in halting the population decline of little terns, their reduction in range has continued. Their vulnerability to disturbance has seen a shift towards fewer, larger colonies in areas where they are free from human disturbance, mostly in fenced off areas or on offshore islands3. Since the SCR, only the colony at Kilcoole, which accounts for over one third of the national population, has been monitored regularly (Figure 8). Numbers there trebled from 18 to 56, immediately after the Seabird Colony Register census but had declined again to 20 AON by Seabird 2000. In 2018, Kilcoole had increased again to 142 AON reflecting the recent Republic of Ireland Seabird Census which recorded 388 little tern AON, an increase of 123% compared to Seabird 20007.

 

Productivity

There is no statistically significant difference in little tern productivity in the Republic of Ireland since monitoring began with an average of 0.94 chicks fledged per pair between 1986 and 2018. 2013 and 2014 were successful breeding seasons, although in 2015 little tern colonies were affected by predation and inclement weather. In 2018, Kilcoole fledged 1.17 chicks per pair after surges associated with Storm Hector destroyed 45 nests. However, many of these pairs re-laid and successfully reared late chick through to fledging8. For the first time in three years, little terns bred again at Baltray, fledging 0.75 chicks per pair9.

 

All Ireland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

315

282

206

% change since previous census   

n/a

-10

-27

*AON = Apparently Occupied Nests

 

Breeding abundance

Little terns only breed in the Republic of Ireland, so all data and text presented for that country is also pertinent to the situation for the whole of Ireland.

 

Productivity

Little terns only breed in the Republic of Ireland, so all data and text presented for that country is also pertinent to the situation for the whole of Ireland.

 

Isle of Man

Population estimates and change 1969–2018 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Isle of Man Census

(2017-18)

Population estimate (AON*)

19

60

20

28

% change since previous census   

n/a

216

-67

+40

*AON = Apparently Occupied Nests

 

Breeding abundance

The Isle of Man little tern population has never been large, with only 19 AON known at the time of Operation Seafarer. Three times as many were present during the Seabird Colony Register, with the peak count of 94 AON occurring shortly after this in 1988, although this had fallen to 20 AON by Seabird 2000. In 2013, trapping of nesting adults resulted in four controls which had fledged as juveniles in 2010; three from other colonies around the Irish Sea and one from a colony on the east coast of Scotland. Immigration may, therefore, be one factor driving the increase in numbers at this colony. A seabird census of the Isle of Man between 2017-18 recorded 28 AON, a 40% increase compared to the number counted during Seabird 200010.

 

Productivity

Few systematic data on the productivity of little terns on the Isle of Man have been collected as part of the SMP.

 

Channel Islands

Little tern does not breed on the Channel Islands.

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UK phenology, diet, survival rates

No data have been collected as part of the Seabird Monitoring Programme.

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References

1 Ratcliffe, N., Pickerell, G. and Brindley, E. 2000. Population trends of Little and Sandwich Terns Sterna albifrons and S. sandvicensis in Britain and Ireland from 1969 to 1998. Atlantic Seabirds, 2, 211–26.

2 Ratcliffe, N. 2003. Little terns in Britain and Ireland: estimation and diagnosis of population trends. In: Schmitt, S. ed. Abstracts Proceedings. 2003 Little Tern Symposium. Royal Society for the Protection of Birds, Sandy.

3 Rendell-Read, S. 2018. Little Tern Newsletter 2017. Unpublished RSPB report, Royal Society for the Protection of Birds, Sandy.

4 Cook, A.S.C.P. and Robinson, R.A. 2010. How representative is the current monitoring of breeding success in the UK? BTO Research Report, No. 573, British Trust for Ornothology, Thetford.

5 Rendell-Read, S. 2017. Little Tern Newsletter 2016. Unpublished RSPB report, Royal Society for the Protection of Birds, Sandy.

6 Cummins, S., Lauder, C., Lauder, A. and Tierney, T. D. 2019. The Status of Ireland’s Breeding Seabirds: Birds Directive Article 12 Reporting 2013 – 2018. Irish Wildlife Manuals, No. 114. National Parks and Wildlife Service, Department of Culture, Heritage and the Gaeltacht, Ireland.

7 Rendell-Read, S. 2019. Little Tern Newsletter 2018. Unpublished RSPB report, Royal Society for the Protection of Birds, Sandy.

8 Johnson, C., Forkan, C. and Newton, S. 2018. Tern Colony Management and Protection at Kilcoole 2018. Conducted under services contract awarded to BirdWatch Ireland by the National Parks and Wildlife Service, Department of Culture, Heritage and the Gaeltacht.

9 Lynch, J, Hartigan, D, Connaghy, M. Martin, B, and Newton, S.F. 2017. Baltray Little Tern Colony Report 2017. Report by Birdwatch Ireland and Louth Nature Trust.

10 Hill, R.W., Morris, N. G., Bowman, & K. A., Wright, D. 2019. The Isle of Man Seabird Census: Report on the census of breeding seabirds in the Isle of Man 2017-18. Manx BirdLife. Laxey, Isle of Man.

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Partners

Data have been provided to the SMP by the generous contributions of its partners, other organisations and volunteers throughout Britain and Ireland. Partners to the SMP are: BirdWatch Ireland; The British Trust for Ornithology; UK Centre for Ecology and Hydrology; Natural Resources Wales; Department of Environment, Food and Agriculture (Isle of Man); Department of Environment, Heritage and Local Government (Republic of Ireland); States of Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage; The National Trust; National Trust for Scotland; Natural England; Northern Ireland Department of Agriculture, Environment and Rural Affairs; The Royal Society for the Protection of Birds; Scottish Natural Heritage; Seabird Group; Shetland Oil Terminal Environmental Advisory Group; Scottish Wildlife Trust. More about the SMP partners >>

 

Image of Little tern appears courtesy of Ian Rendall ©, is subject to international copyright law and may not be reproduced in any form whatsoever.

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SMP Report 1986–2018

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