Common Tern

Listen to example recordings of the main vocalisations of Common Tern, provided by xeno-canto contributors.

This species can be found on the following statutory and conservation listings and schedules.

UK Birds of Conservation Concern	Amber listed
Species of European Conservation Concern	Least Concern
IUCN Red List of Threatened Species (global)	Least Concern
Schedule 1 license required (to disturb)	No
Birds Directive Annex 1	Yes
Listed on the Annexes of	WBD(I), Bern(III), Bonn(II*), AEWA

Common Terns breed at lakes and reservoirs scattered across lowland Britain, especially in the major river valleys, and extensively at the coast. There are a few very large coastal colonies and groups of colonies that account for more than half the total population. Breeding numbers and productivity at sample colonies have been monitored annually since 1986 by JNCC's Seabird Monitoring Programme. The abundance trend shows approximate stability from 1986 to 2018 with some small fluctuations, equating to a 9% increase over this period (although this is not statistically significant), while productivity has fluctuated but appears to show a recent decline (SMP data here).

Common Terns are poorly covered by general breeding bird surveys because of their highly aggregated breeding population. There have been enough birds seen on BBS visits for a trend to be drawn but this has an exceptionally wide confidence interval and probably relates mainly to birds seen on overland passage, prospecting for nest sites or breeding in small, dispersed colonies. Extraordinary counts in 2017 and very high counts in 2014 have caused an upturn in the BBS index, but other recent counts have been similar to those from previous years.

Breeding Common Terns are widespread and primarily coastal in Scotland and are found on the lochs and islands of the west coast, Outer Hebrides, Northern Isles and around the inner Moray Firth. This contrasts with England, where the species’ range is dominated by inland colonies. In Ireland, colonies are more clustered, both on the coast and inland where most nest on islands in the largest lakes.

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Occupied 10-km squares in UK

No. occupied in breeding season	669
% occupied in breeding season	22
No. occupied in winter	15
% occupied in winter	0.5

European Distribution Map

European Breeding Bird Atlas 2

Breeding Season Habitats

Most frequent in

Estuaries

The breeding distribution change map shows a clear pattern of losses in Scotland and Ireland contrasting with gains in eastern and central England since both previous breeding atlases.

Common Tern is a summer breeding species, present from April onwards, departing from August onwards.

View a summary of recoveries in the Online Ringing Report.

Foreign locations of birds ringed or recovered in Britain & Ireland

View number ringed each year in the Online Ringing Report

Maximum Age from Ringing	33 years 0 months 6 days (set in 1996)
Typical Lifespan	12 years with breeding typically at 3 year
Adult Survival	0.9
Juvenile Survival	0.47 (to age 2)

Wing Length	Adults	271.2±6.5 | Range 260–281mm, N=304
	Juveniles	261.8±8.6 | Range 247.5-275.5mm, N=120

Body Weight	Adults	128±9.6 | Range 113–144g, N=429
	Juveniles	127±13.7 | Range 106–153g, N=124

Feather measurements and photos on featherbase

Ring size	C2
Field Codes	2-letter: CN | 5-letter code: COMTE | Euring: 6150

For information in another language (where available) click on a linked name

Causes of change

There is little good evidence available regarding the drivers of the breeding population change in this species in the UK.

Further information on causes of change

No further information is available.

Information about conservation actions

The reasons for the declines at coastal colonies are not clear and a wide range of potential conservation actions have been suggested by different authors. These include the control of predators such as rats (Amaral et al. 2010) and gulls (Blokpoel et al. 1997), including selectively controlling chick-predating gulls in Canada (Guillemette & Brousseau 2001); providing plywood shelters for chicks to reduce predation (Burgess & Morris 1992); actions to reduce disturbance such as restricting access to nesting areas (Fasola & Canova 1996) and educating watercraft owners about the effects of disturbance (Burger & Leonard 2000); and habitat management to reduce vegetation (Cook-Haley & Millenbah 2002). In the latter study, vegetation was reduced through spraying and nest success was highest in areas with moderate amounts (40-50%) of vegetation cover.

In Maryland, USA, McGowan et al. (2019) successfully relocated a colony affected by construction work to a new site 200 m away, using a combination of deterrents (overhead lines) at the old site and attractants (audio calls and decoys) at the new site. However, they caution that this approach should only be used when absolutely essential and note that whilst in this case there were no apparent effects on reproduction, this approach may not be viable on all sites.

It is currently unclear which action or actions are most likely to help reverse declines and hence further research may be needed to inform conservation policies. Denac & Bozic (2020) give an account of a wide variety of conservation measures undertaken to provide and enhance breeding habitat for Common Terns in Slovenia, including various actions to manage vegetation, reduce predation and increase nest site availability by preventing Black-headed Gulls from occupying sites (the latter by blocking access until terns had returned using a grid of plastic strings), The success (or failure) of the conservation actions are discussed, although this is largely subjective and the efficacy of the various measures have not been tested experimentally.

Away from coastal sites, the provision of nesting rafts has proved a successful method to attract Common Terns to previously unoccupied inland sites (Dunlop et al. 1991).