Little Tern Sternula albifrons

Status;  International importance;  Population estimates;  Distribution;  Annual abundance/ productivity; Phenology/diet/survival

 

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Description

Little Tern vignette

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:

Amber listed in Birds of Conservation Concern 4 (2015 update)

Wildlife and Countryside Act 1981 - protected under Schedule 1

EC Birds Directive - listed in Annex 1 and as a migratory species

(further information on Conservation Designations for UK Taxa)

Amber listed in Birds of Conservation Concern in Ireland 2014-2019 (2014 update)

 


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.

 


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.

 


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 (PDF, 566 kb).

 

An interactive map is available on the NBN Gateway, where you can filter to display only the Seabird 2000 data.  For more recent, but less comprehensive, coverage view the distribution on the NBN with all available contributing datasets.

 

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

 


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% CLs 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.   

 



 

Breeding abundance

 

Little tern UK abundance graph 1986-2015

Figure 1: Trend in UK abundance index (solid line) of little tern 1986-2014 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

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 2015, the index was based at 66% below the baseline, the second lowest value ever recorded since 1986. In 2015, data were received from 93 colonies although 33 of these recorded no nesting little terns (cf. 76 and 39 respectively in 2014); monitored colonies held 1,300 AON. Prior to the period shown above, little tern abundance had been declining 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 Productivity UK 2015

Figure 2: Trend in UK productivity (no. of chicks fledged per pair) of little tern 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The productivity of little terns has been relatively low throughout the recording period, although with a great deal of annual fluctuation since the low point 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 the 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, chiefly, 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 tide edge, 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 realignment of coastal defences may create new opportunities for nesting.

 

Analysis of the SMP dataset found mean breeding success remained relatively stable at around 0.51 chicks per nest per year between 1986 and 20083. The quality of the dataset indicated that a fall of 10% or less in breeding success may not be detected, although a change in success of 25% or more would be detected with confidence. At this rate of breeding success, 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 breeding success were to increase to 0.70, population decline would be averted, and the population would stabilise.

 

 

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 Scottish colonies abundance 2015

Figure 1: Trend in abundance of little tern at two major Scottish colonies, 1986-2015.

 

The Scottish population of little tern increased between Operation Seafarer and the Seabird Colony Register but had fallen again by the time of Seabird 2000. The few colonies surveyed each year do not allow for an accurate 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 (Gordon) have almost halved whereas at Tiree Reef (Argyll and Bute) numbers have been more stable although may now be in decline, with low numbers recorded there in 2001, 2003, 2010, 2013 and also in 2015. At Sands of Forvie, an electric fence kept out the majority of ground predators, such as Foxes and Badgers (Meles meles) however, all 19 AON failed at the egg stage in 2015, probably due to a combination of poor weather and avian predation4. Tiree holds the largest concentration of little terns in Scotland where, in addition to the main colony, many smaller colonies are scattered around the island in most years, each usually holding from a few up to 10 pairs. However, in 2015, these satellite colonies held only a further nine pairs, the majority were at just one colony (three pairs) with nine of the 17 colonies visited deserted. Numbers of little terns nesting on Tiree were well below the average of the previous 12 years (53 AON per year). However in 2015, numbers nesting on the nearby islet of Gunna were unusually high at 45 AON, suggesting a shift to that location, particularly from the adjacent Tiree colony of Miodar, which dropped from 25 pairs in 2014 to just three pairs in 20155, 6.  

 

Productivity

 

Scotland Little tern productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of little tern in Scotland, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Aside from the obvious peaks in productivity in 1986, 1988, 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 outside the country. In 2014, nesting little terns had a very productive breeding season while in 2015 productivity fell to the second lowest value recorded. Out of 13 colonies that reported productivity this year, only three bred successfully producing a total of 15 chicks (cf 116 chicks in 2014). At Sands of Forvie, the number of breeding pairs has been steadily increasing by two or three pairs per year since at least 2005, however, in 2015 all chicks failed at egg stage, due to a combination of poor weather and avian predation4. On Tiree little terns had a very poor breeding season with zero productivity, following moderate to good breeding success in the previous six years. In 2015, eight of 17 colonies held only 34 AON with all these failing to produce a chick due to poor weather6.

 

 

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 abundance graph 1986-2015

Figure 1: Trend in abundance index (solid line) of little tern in England, 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

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 proscriptions due to 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 at the time of Seabird 2000 (1,541 AON); at least 1,154, 1,100 and 959 AON were recorded in 2013, 2014 and 2015, respectively, although data are not submitted to the SMP for all colonies.

 

Productivity

 

England Little tern productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of little tern in England, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Productivity recorded at English colonies has also fluctuated much 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 not sufficient 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 both 2012 and 2013, data were received from 31 colonies but each year five colonies held no breeding little terns at all and complete failure was recorded in a further 17 and 13 colonies, respectively. 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.

 

 

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 Gronant abundance 2015

Figure 1: Abundance of little terns at Gronant (Clwyd), 1986-2015.

 

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 (Clwyd), 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 135 AON, with one pair breeding at Ayr of Point (<4km to the East)7.

 

Productivity

 

At Gronant (Clwyd) an average of 0.75 chicks per pair was fledged each year between 1986 and 2015. Peaks in productivity were recorded at Gronant (Clwyd) in 1992, 2003, 2004 and 2010, all ranging between 1.78 and 1.92. In 2015, productivity was just above the average with 0.80, 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 two sites bred successfully.

In contrast to previous years, the first recorded egg was not until 7 June. Subsequently, terns seemed reluctant to re-lay in 2015 after losing their first clutch and unusually none were recorded.

The 2015 season also saw eggs and newly hatched chicks to be much smaller on average than usual (pers comm. Prof David Norman). Possibly this was due to adults struggling to feed in both the bad weather and uncharacteristic tide conditions so were generally in poor condition at the start of the breeding season. In addition, high kestrel predation restricted breeding success and accounted for the loss of 33 chicks, eight fledglings and three little tern adults6.

 

 

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 pairs were recorded during Operation Seafarer, declining to two pairs 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.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*) 309 280 206
% change since previous census    N/a -9 -26

 

* AON = Apparently Occupied Nests

 

Breeding abundance

 

Figure 1: Abundance of little terns at Kilcoole (Co. Wicklow), 1986-2015.

 

The little tern population of the Republic of Ireland has undergone long-term decline since Operation Seafarer, although the scale of the decline, at -33% between the first and most recent national censuses, has not been large. The increased use of beaches as a recreational resource from the middle of the 20th century onwards led to severe population losses and the abandonment of many traditional colony sites5. While guarded colonies have succeeded in halting the population decline in little terns, their reduction in range has continued. Their vulnerability to disturbance has seen a shift towards fewer, larger colonies in the remaining areas where they are free from human disturbance, mostly in fenced off areas or on offshore islands5. Since the SCR, only the colony at Kilcoole (Co. Wicklow), usually the largest one in the country, has been monitored with any regularity (Figure1). Numbers there trebled, from 18 to 56, immediately after the Seabird Colony Register census, but had declined again by Seabird 2000. However, the largest increases have occurred since then, with over 100 pairs recorded in several recent years, including 2014 and 2015 when 120 and 155 AON were counted, respectively. Three other colonies surveyed in 2015 held at least 230 nesting pairs thus, at just below 400 pairs breeding in 2015, the national population is almost twice the size as recorded during Seabird 2000. 

 

Productivity

 

There is no statistically significant difference in little tern productivity in the Republic of Ireland since monitoring began with an average of 0.46 chicks fledged per pair between 1986 and 2015. 2013 and 2014 were successful breeding seasons, although in 2015 little tern colonies were affected by predation and inclement weather. Kilcoole (Co.Wicklow) fledged 1.87 chicks per pair and Baltray (Co. Louth), which suffered heavily from predation, fledged  0.80 chicks per pair6. Wet and windy weather conditions during June and July affected productivity levels, as did predation by Peregrine falcon and Great black-backed gulls6.

 

 

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 tern Abundance Kilcoole 2015

Figure 1: Abundance of little terns at Kilcoole, 1986-2014.

 

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 All-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 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*) 19 60 20
% change since previous census    N/a +216 -67

 

* AON = Apparently Occupied Nests

 

Breeding abundance

 

Little tern Ayres of Man abundance 2015

 

Figure 1: Abundance of little terns at The Ayres (Isle of Man), 1986-2015.

 

Little terns now only nest in one area of the Isle of Man. The population has never been large with only 19 pairs known at the time of Operation Seafarer. Three times as many were present at the site during the Seabird Colony Register, with the peak count of 94 pairs occurring shortly after this in 1988, but this had fallen to 20 pairs again by Seabird 2000. Over the last decade, numbers had remained fairly stable, usually ranging between 10-20 pairs, but 50-55 pairs nested in 2014 with similar numbers in 2015 when 48 pairs were present at the colony. In 2013, trapping of nesting adults resulted in four controls, all of which had fledged as juveniles in 2010; three were from other colonies around the Irish Sea but one was from a colony on the east coast of Scotland. Immigration may be one factor currently increasing the numbers recorded at the colony. 

 

Productivity

 

Few systematic data on the productivity of little terns on the Isle of Man have been collected as part of the SMP. On average, 0.52 chicks have been fledged per pair per year between 1991 and 2015.

 

 

Little tern does not breed on the Channel Islands.

 

 


UK phenology, diet, survival rates

 

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

 


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 Proc. 2003 Little Tern Symp. Royal Society for the Protection of Birds, Sandy.

3 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, BTO, Thetford. 

4 Short, D. and  Watts E. 2016. Breeding of four species of tern and Black-headed Gull at Forvie National Nature Reserve, 2015. Unpublished report, Scottish Natural Heritage, Aberdeen.

5 Rendell-Read, S. 2015. Little Tern Newsletter 2014. Unpublished report, Royal Society for the Protection of Birds, Sandy.

6 Rendell-Read, S. 2016. Little Tern Newsletter 2015. Unpublished report, Royal Society for the Protection of Birds, Sandy.

7 Hibbert, A. 2016. Gronant Little Tern (Sternula albifrons) Report 2015. Unpublished report, Denbighshire County Council Countryside Service.

 


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; 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 Environment Agency; 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.