Marine bird breeding success

The UK target was met in the Celtic Seas, but not in the Greater North Sea where 35% of species experienced frequent, widespread breeding failures between 2010 and 2015. In both sub-regions, the species that frequently failed to raise young, typically gulls and terns, feed on small fish at the surface.

Background

UK Target on Marine Bird Population Condition – breeding success/failure

This indicator is used to assess progress against the following target, which is set in the UK Marine Strategy Part One (HM Government, 2012): “At the scale of the Marine Strategy Framework Directive sub-regions marine bird productivity is not significantly affected by human activities: widespread seabird colony breeding failures should occur rarely in other species that are sensitive to changes in food availability.”

Key pressures and impacts

The extent and frequency of seabird breeding failure is used as an indicator of seabird population health. The indicator could provide evidence of fishing impacts where fisheries and seabirds target the same prey and other impacts from human disturbance, contaminants, and predation by invasive species such as rats. Natural factors may also affect this indicator, such as climate-driven changes in prey-fish availability, and predation and disturbance from native predators such as the fox. Distinguishing between natural effects and human impacts on breeding performance is not always possible.

Measures taken to address the impacts

Management measures at breeding colonies and in offshore areas that are protected by UK and European legislation are likely to help increase the resilience of seabirds to the impacts of climate change. There is evidence that the sandeel fishing closure off North-East England and East Scotland has had a positive impact on the breeding success of local kittiwake colonies. The recent change to smaller scale management of sandeel stocks may also have benefits for the seabirds that feed on them.

Assessment method

The methods used in this UK assessment are identical to those used for the OSPAR Intermediate Assessment (OSPAR Commission, 2017), for which the assessment and development of the indicator was led by the UK. The process was developed by the UK Healthy and Biologically Diverse Seas Evidence Group and in (Cook and others, 2014a). They were agreed to be technically appropriate for application in the North East Atlantic by the Joint OSPAR, ICES, and HELCOM Working Group on Marine Birds (ICES, 2016).

The breeding failure assessments for each species were constructed from the time series (1991 to 2015) of the annual estimates of breeding success (number of chicks fledged per pair, clutch or nest) at a sample of colonies. A separate assessment was conducted for each sub-region. The assessment of the Greater North Sea includes data from all countries bordering the sub-region, except France. An assessment was also conducted for each sub-division of the Greater North Sea, as shown in Figure 1. The assessment of the Celtic Seas is based on data from the UK and Ireland. The assessment of this indicator for the OSPAR Intermediate Assessment (OSPAR Commission, 2017) also included the Arctic Waters of Norway, which provides a useful comparison with this UK assessment because some species breed in all three regions and some Arctic breeders overwinter in UK waters only. Because not all colonies in the sample will have been observed every year in the time series, missing annual observations were predicted using models.

Figure 1: Marine bird assessment units.

Species-Specific Assessment of Breeding Failure

Parameter/metric

‘Annual colony failure rate,’ that is, the percentage of colonies failing per year, per species (Cook and others, 2014a).

‘Failure’ is defined as when a colony fails to produce any young or produces very few young during a single breeding season. Failure is quantified by (Cook and others, 2014a) as when the mean annual productivity of a breeding colony drops to 0.1 or fewer chicks per pair within a clutch or nest. As failure could be interpreted as an unusual deviation from ‘normal’ levels of breeding success, the precise assessment value below which a colony is defined as failing may be different at some colonies, even for the same species. The assessment value used for determining failure can be adjusted according to the knowledge of the colonies in question. Ideally, the assessment value should be taken from any clear response to important environmental factors such as low food availability (Cury and others, 2011). The assessment value of 0.1 chicks per pair, clutch or nest should be used as a default assessment value unless there is good evidence to show that ‘failure’ of some species in some areas should be set at a different level (ICES, 2016).

Trend analysis

The assessments for each species are constructed from a time-series of annual estimates of breeding success at a sample of colonies. Not all the colonies in the sample will have been observed every year in the time-series. Missing annual observations were estimated using a Generalised Linear Model (GLM) framework with a binomial error structure (Cook and others, 2014a; 2014b). Breeding success for each colony in each year was calculated, and where this value was 0.1 or fewer chicks per pair, clutch or nest, the colony was assessed as having failed in that year. Breeding success or failure was modelled in relation to year and site, to account for the fact that not all sites were covered in all years. The coefficient for each year was then taken to represent the probability of breeding failure occurring at any given site within that calendar year. The parameter ‘Year’ was included in the Generalised Linear Model as a fixed effect factor, rather than a random effect so that the coefficients would not be constrained to follow a normal distribution.

To minimise the impact of differences in sampling rate and ensure that breeding success was likely to be representative of the colony, minimum criteria were set for inclusion of data within the model. Only those colonies at which a mean of 10 nests were monitored for at least three years were considered. To prevent any individual site having undue influence over the value of the coefficients, a jack-knife statistical approach was used in which each site, in turn, is dropped from the model. Models were run for each species in each sub-region in turn. The final indicator value presented for each species, in each sub-region, and in each year is the mean probability of a breeding failure calculated from each run of the jack-knife analysis.

Assessment

In summary, ‘breeding failure’ is when the annual mean breeding success of a colony is 0.1 or fewer chicks per pair, clutch or nest, and ‘annual colony failure rate’ is the percentage of colonies of species that are experiencing breeding failure in a single breeding season.

1. Breeding failure for each species was assessed in two stages: Assessing if colony failure is widespread - the annual colony failure rate (the percentage of colonies experiencing breeding failure) is considered ‘widespread’ if it exceeds the assessment values set for each species (see below); and

2. Assessing the frequency of widespread breeding failure occurrence. Widespread breeding failure is considered ‘frequently occurring’ if it occurs in more than three years out of six.

The annual colony failure rate (the percentage of colonies failing) of each species was assessed for each region and depending on species, against one of the two upper thresholds. For terns the threshold was mean percentage of colonies failing per year, over the preceding 15 years, and for all other species 5% of colonies failing per year. The aim of these thresholds for annual colony failure rate is to identify widespread breeding failures and to differentiate large-scale impacts from local problems, where only a small proportion of colonies fail per year. The above assessment values were taken from Cook and others (2014a) who tested various threshold values for each species. A different threshold value was applied to the breeding failure rate of terns because they often desert colonies, sometimes before laying eggs, in response to local disturbances or impacts on food supply (Shealer and Kress, 1991; Holt, 1994; Cook and others, 2011). The threshold value for terns is designed to identify years of unusually high rates of breeding colony failure. A fixed threshold value of 5% was appropriate for all other species that do not tend to desert colonies all at once. Cook and others (2014a) found that years in which colony failure rate is more than 5% are much rarer in other species and they, therefore, provide a good indicator that pressures may be impacting on the population.

For each species, the frequency of widespread colony failure was assessed over the most recent six-year period from 2010 to 2015, inclusive. The six-year period was chosen to match the EU’s Marine Strategy Framework Directive reporting cycle. To assess a species over a certain period, there needed to be some observed data of breeding success at some colonies during 2015 (the most recent year in the period). One or two years of widespread colony failure were considered as ‘acceptable,’ given that seabird species are long-lived and given the wide range of possible natural and anthropogenic factors that could cause breeding failure in some species. There is likely to be an impact of successive years of breeding failure on a colony. If widespread, successive colony failures could have a significant impact on the recruitment of breeding birds into the regional population. Low recruitment could lead to declines in population size and affect the assessments of the UK indicator on marine bird abundance. Cook and others (2014a) recommended that widespread failure of a species in three years out of six should be flagged as a cause for concern and that failure in more than three years was not consistent with achieving the UK target.

Species selection and Aggregation (functional groups)

There were sufficient time series data to conduct assessments of 20 species in the Greater North Sea and Celtic Seas during 2010 to 2015. Table 1 presents the five marine bird functional groups. The species assessed in each sub-region were all seabirds from two of the five functional groups (surface feeders and water column feeders). The species assessed and the functional groups to which they were assigned, are presented in Table 2.

Table 1. Marine bird functional groups.

Functional Group	Typical Feeding Behaviour	Typical Food Types	Additional Guidance
Wading feeders	Walk/wade in shallow waters	Invertebrates (molluscs, polychaetes, etc.)	Example: oystercatcher
Surface feeders	Feed within the surface layer (within 1m to 2m of the surface)	Small fish, zooplankton and other invertebrates	“Surface layer” defined on the normal diving depth of plunge-divers (except gannets) Example: Black-legged kittiwake
Water column feeders	Feed at a broad depth range in the water column	Pelagic and demersal fish and invertebrates including squid and zooplankton	Include only species that usually dive and actively swim underwater, including gannets and species that feed on benthic fish like flatfish. Example: The common guillemot
Benthic feeders	Feed on the seabed	Invertebrates such as molluscs, echinoderms	Example: common eider
Grazing feeders	Grazing in intertidal areas and shallow waters	Plants such as. eelgrass, saltmarsh plants and algae	Geese, swans and dabbling ducks, coot Example: mallard

Table 2. Species included in assessment of marine bird breeding success/failure 2015, in each sub-region.

		Functional groups					Assessment Region
Species (English Name)	Species (Scientific Name)	Grazing feeders	Wading feeders	Surface feeders	Water column feeders	Benthic feeders	Arctic	Greater North Sea	Celtic Seas
Red-throated diver	Gavia stellata				X
Black-throated diver	Gavia arctica				X
Great Northern diver	Gavia immer				X
White-billed diver	Gavia adamsii				X
Great crested grebe	Podiceps cristatus				X
Red-necked Grebe	Podiceps grisegena				X
Slavonian grebe	Podiceps auritus				X
Northern Fulmar	Fulmarus glacialis			X	(X)		X	X	X
Sooty Shearwater	Puffinus griseus			X	(X)
Manx Shearwater	Puffinus puffinus			X	(X)				X
Balearic shearwater	Puffinus mauretanicus			X	(X)
Cory's Shearwater	Calonectris diomedea			X	(X)
European Storm-petrel	Hydrobates pelagicus			X	(X)
Leach's Storm-petrel	Oceanodroma leucorhoa			X	(X)
Northern gannet	Morus bassanus			(X)	X		X	X	X
Great Cormorant	Phalacrocorax carbo				(X)	X	X	X
European shag	Phalacrocorax aristotelis				X	(X)	X	X	X
Eurasian spoonbill	Platalea leucorodia		X					a
Mute Swan	Cygnus olor	X
Bewick's Swan	Cygnus bewickii	X
Whooper Swan	Cygnus cygnus	X
Greylag goose	Anser anser	X
Greenland white-fronted goose	Anser albifrons flavirostris	X
Canada Goose	Branta canadensis	X
Barnacle Goose	Branta leucopsis	X
Brent Goose	Branta bernicla	X
Shelduck	Tadorna tadorna		X
Wigeon	Anas penelope	X
Teal	Anas crecca		X
Mallard	Anas platyrhynchos	X	X
Pintail	Anas acuta	X	X
Shoveler	Anas clypeata	X
Pochard	Aythya ferina					X
Tufted Duck	Aythya fuligula					X
Greater Scaup	Aythya marila					X
Common Eider	Somateria mollissima					X		a
King eider	Somateria spectabilis					X
Steller’s eider	Polysticta stelleri					X
Long-tailed Duck	Clangula hyemalis					X
Common Scoter	Melanitta nigra					X
Velvet Scoter	Melanitta fusca					X
Goldeneye	Bucephala clangula					X
Common merganser	Mergus merganser				X
Red-breasted Merganser	Mergus serrator				X
Smew	Mergellus albellus				X
Coot	Fulica atra	X
Oystercatcher	Haematopus ostralegus		X					a
Black-winged Stilt	Himantopus himantopus		X
Pied avocet	Recurvirostra avosetta		X					a
Lapwing	Vanellus vanellus		X
Golden plover	Pluvialis apricaria		X
Grey Plover	Pluvialis squatarola		X
Ringed plover	Charadrius hiaticula		X
Kentish Plover	Charadrius alexandrinus		X
Bar-tailed Godwit	Limosa lapponica		X
Whimbrel	Numenius phaeopus		X
Curlew	Numenius arquata		X
Spotted Redshank	Tringa erythropus		X
Redshank	Tringa totanus		X
Greenshank	Tringa nebularia		X
Wood Sandpiper	Tringa glareola		X
Turnstone	Arenaria interpres		X
Red-necked Phalarope	Phalaropus lobatus			X
Grey Phalarope	Phalaropus fulicarius			X
Red Knot	Calidris canutus		X
Sanderling	Calidris alba		X
Little Stint	Calidris minuta		X
Curlew Sandpiper	Calidris ferruginea		X
Purple sandpiper	Calidris maritima		X
Dunlin	Calidris alpina schinzii & arctica		X
Ruff	Philomachus pugnax		X
Arctic skua	Stercorarius parasiticus			X				X	X
Long-tailed Skua	Stercorarius longicaudus			X
Pomarine Skua	Stercorarius pomarinus			X
Great Skua	Stercorarius skua			X			X	X	X
Glaucous gull	Larus hyperboreus			X			X
Great Black-backed Gull	Larus marinus			X			X	X	X
Herring gull	Larus argentatus		X	X			X	X	X
Lesser black-backed gull	Larus fuscus intermedius/graellsii		X	X			X	X	X
Common Gull	Larus canus		X	X				X	X
Mediterranean Gull	Larus melanocephalus			X					a
Black-headed Gull	Croicocephalus ridibundus		X	X				X	X
Little Gull	Larus minutus			X
Black-legged kittiwake	Rissa tridactyla			X			X	X	X
Ivory gull	Pagophila eburnea			X
Little Tern	Sternula albifrons			X				X	X
Roseate tern	Sterna dougallii			X				X
Common tern	Sterna hirundo			X				X	X
Arctic tern	Sterna paradisaea			X				X	X
Sandwich tern	Sterna sandvicensis			X				X	X
Black Tern	Chlidonias niger			X
Razorbill	Alca torda				X		X	X	X
Common Guillemot	Uria aalge				X		X	X	X
Brünnich’s guillemot	Uria lomvia				X		X
Black Guillemot	Cepphus grylle				X		X		X
Little Auk	Alle alle				X		X
Puffin	Fratercula arctica				X		X	X	X

Results

Findings from the 2012 UK Initial Assessment

This indicator was not considered as part of the UK Initial Assessment (HM Government, 2012).

Latest findings

Status assessment

In the Celtic Seas and the Greater North Sea, a quarter or more of species showed frequent and widespread breeding failures during the period from 2010 to 2015 (Tables 3 and 4) Of the six water-column feeding species in the Greater North Sea and Celtic Seas, none showed frequent and widespread breeding failures during 2010 to 2015, compared to 36% (Celtic Seas) and 50% (Greater North Sea) of surface feeding species (Table 3). Surface-feeders forage on small fish, zooplankton and other invertebrates at or within the surface layer (within 1 to 2m of the surface); water column feeders actively dive below the surface to a broad range of depths to feed on fish and invertebrates such as squid and zooplankton in the water column or close to the seabed.

Table 3. Percentage of species that experienced frequent, widespread colony failures between 2010 and 2015.

	Greater North Sea	Celtic Seas
Surface feeding species	50% (14)	36% (14)
Water column feeding species	0% (6)	0% (6)
All species	35% (20)	25% (20)

Table 4. Number of years of widespread breeding failure of seabird species from 2010 to 2015 in the Greater North Sea and Celtic Seas. ‘Widespread breeding failure’ occurs when the percentage of colonies failing per year exceeds the mean percentage over the preceding 15 years for tern species or exceeds 5% for all other species. n.a. = not applicable: insufficient data or not breeding.

	Species (Common Name)	Greater North Sea	Celtic Seas
Surface Feeders	Black-headed gull	≥ 4	≥ 4
	Northern fulmar	≤ 2	≤ 2
	Herring gull	≤ 2	≥ 4
	Common gull	≥ 4	≥ 4
	Lesser black-backed gull	≥ 4	≥ 4
	Great black-backed gull	≥ 4	≤ 2
	Manx shearwater	n.a.	≤ 2
	Black-legged kittiwake	≥ 4	≤ 2
	Arctic skua	≥ 4	≤ 2
	Greats skua	≤ 2	≤ 2
	Roseate tern	≤ 2	n.a.
	Common tern	3	≥ 4
	Arctic tern	≤ 2	≤ 2
	Sandwich tern	≥ 4	3
	Little tern	≤ 2	≤ 2
Water Column Feeders	Razorbill	3	≤ 2
	Black guillemot	n.a.	≥ 2
	Puffin	≤ 2	≤ 2
	Northern gannet	≤ 2	≤ 2
	European shag	≤ 2	≤ 2
	Great cormorant	≤ 2	n.a.
	Common guillemot	≤ 2	≤ 2

Trend assessment

Breeding success is declining in the Celtic Seas and the Greater North Sea. In both sub-regions, more species (mainly surface feeders) experienced widespread failure between 2010 and 2015, than during the 2000s when the UK Initial Assessment (HM Government, 2012) was conducted (Figure 2). There is moderate/low confidence in the methodology used and moderate confidence in the data coverage.

Figure 2. Changes in the proportion of marine bird species which have not experienced widespread annual colony failures in each year. The maximum number of species included per year in each group is shown in brackets in the figure legend. The number of species varied each year depending on data availability.

Further information

Species-specific Assessments

Separate assessments were carried out for the Greater North Sea and the Celtic Seas. The OSPAR Assessment (OSPAR Commission, 2017) also included Arctic Waters: Norwegian areas only, including Svalbard and Jan Mayen. The annual colony failure rate of each species was plotted separately for each region. Figure 3 shows species specific indicator assessments of annual colony failure. The common eider, Eurasian spoonbill, pied avocet, and oystercatcher were omitted from the regional assessment (Table 3) because the time series did not contain an estimate of breeding success in 2015. Roseate tern colony failure rates for the Celtic Seas are not included in the regional assessment in Table 3 because there were no data for roseate tern colonies in Ireland since 2013. The maps in Figure 3 can be used to identify spatial patterns in breeding failure occurrence in all the species assessed.

Figure 3. Fulmar: example of species-specific indicator assessments of annual colony failure between 1986 and 2015. Assessment values are shown as red dotted lines. The assessment value for tern species is the mean percentage of colonies failing per year, over the preceding 15 years. The assessment value for all other species (except terns) is 5% of colonies failing per year. The black dotted line denotes the mean percentage of colonies failing per year, over the preceding 15 years, where this is not used as the assessment value. All values below the assessment value are coloured green, and all those above are coloured red and indicate ‘widespread breeding failure’.

Figure 4. Fulmar: example of spatial distribution in breeding colony failures of each species. Pie charts show the proportion of years between 2010 and 2015 in which breeding success was more than 0.1 chicks per pair (green), or 0.1 or fewer chicks per pair (red). Grey indicates several years in which breeding success was not measured.

The assessment was also conducted in each of the six sub-divisions of the Greater North Sea (see Figure 1) and results are shown in Figure 5. The assessments in some sub-divisions were limited by data availability and should be viewed with caution. However, Figure 5 does demonstrate how this indicator assessment can be disaggregated into smaller assessment units. The subdivisions which had incomplete spatial coverage of data were:

• Sub-division (c) - Skagerrak/Kattegat – data limited to the Norwegian coast
• Sub-division (d) - Southern North Sea – data limited to the UK, Belgium, and Netherlands coasts
• Sub-division (e) - The English Channel - data limited to the UK coast, Jersey and Guernsey

Figure 5. Species-specific assessments of annual colony failure in the sub-divisions of the Greater North Sea. Species ordered by functional group. Colour of cells indicates the number of years during the six-year assessment period (2010 to 2015) that annual colony failure rate was widespread and that it exceeded species-specific assessment values: green = two years or less; orange cells = three years; red = four years or more. Greater North Sea sub-divisions are: a) North-east coast of Britain; b) west coast of Norway; c) Skagerrak/Kattegat; d) Southern North Sea; e) The English Channel; f) North coast of Scotland and the Northern Isles.

Conclusions

The UK target was met in the Celtic Seas, but not in the Greater North Sea, where 35% of species experienced frequent, widespread breeding failures between 2010 and 2015. In both sub-regions, the species that frequently failed to raise young all feed on small fish at the surface. Species that dive below the surface in pursuit of fish showed widespread breeding failures much less frequently. This would suggest the surface availability of small forage fish species including lesser sandeel and sprat is limiting the breeding success of surface-feeding species such as the black-legged kittiwake. Reductions in food availability could be a result of climate change or due to past and present fisheries.

The reduction of other pressures on seabirds through active management at colonies in the UK will help to enhance the resilience of the UK’s breeding seabirds to the impacts of climate change on their natural food supply.

Knowledge gaps

Climate change effects on prey availability are likely to increase the incidence of widespread breeding failures in UK seabirds in the future. A better understanding of the impact of human activities is required to better manage the reduction of human impacts on breeding seabirds and increase their resilience to the effects of climate change. For instance, can this indicator be used to inform the management of sandeels?

Further information

This indicator was developed by the UK Healthy and Biologically Diverse Seas Evidence Group subgroup on marine birds, by Cook and others (2014a) and by the ICES/OSPAR/HELCOM Joint Working Group on Marine Birds assessment, but some limitations were acknowledged (ICES, 2015). The assessment methods for the marine bird breeding success/failure indicator currently focus on the extreme events of almost no chicks being produced by a colony, on average, per year. In doing so, they fail to identify other years where poor breeding success could still have significant negative impacts on the population in the longer term. However, it is not straightforward to categorise annual breeding success as ‘good’ or ‘poor.’ The reason breeding has not been directly assessed as ‘good’ or ‘poor’ in this indicator is because the number of chicks that need to be produced each year to sustain or increase a population varies substantially as do survival rates and other demographic parameters. Information on demographics like survival rate, age at first breeding, and immature survival rates are more resource demanding to measure because of the need to monitor the breeding success of individual birds from year to year. For well-studied species and at a few intensively studied sites these data do exist.

A possible step forward towards setting more informed and objective targets for annual breeding success rates would be to collate an inventory of ongoing monitoring of survival rates in the North-East Atlantic and conduct a review of published estimates. Once survival estimates and other demographics have been collated, some simple population modelling could be undertaken to produce some preliminary estimates of the levels of breeding success required to sustain or increase the population.

References

Cook ASCP, Calbrade NA, Austin GE, Burton NHK (2011) ‘Determining foraging use of the Dee estuary by common terns from the recent declining colony at the Shotton Lagoons and Reedbeds SSSI’ BTO report to CCW, Thetford.

Cook ASCP, Robinson RA, Ross-Smith VH (2014a) ‘Development of MSFD Indicators, Baselines and Target for Seabird Breeding Failure Occurrence in the UK (2012)’ JNCC Report 539, ISSN 0963 8901 (viewed on 23 October 2018)

Cook ASCP, Dadam D, Mitchell I,Ross-Smith VH, Robinson RA (2014b) ‘Indicators of seabird reproductive performance demonstrate the impact of commercial fisheries on seabird populations in the North Sea’ Ecological Indicators 38: 1–11 (viewed on 23 October 2018)

Cury PM, Boyd IL, Bonhommeau S, Anker-Nilssen T, Crawford RJM, Furness RW, Mills JA, Murphy EJ, Österblom H, Paleczny M, Piatt PF, Roux J-P, Shannon L, Sydeman WJ (2011) ‘Global seabird response to forage fish depletion – one-third for the birds’ Science 334: 1703–1706 (viewed on 23 October 2018)

HM Government (2012) ‘Marine Strategy Part One: UK Initial Assessment and Good Environmental Status’ (viewed on 5 July 2018)

Holt DW (1994) ‘Effects of short-eared owls on common tern colony desertion, reproduction, and mortality’ Colonial Waterbirds, 17, 1-6 (viewed on 28 October 2018)

ICES (2015) ‘Report of the Joint ICES/OSPAR Working Group on Seabirds (JWGBIRD)’, 17–21 November 2014, Copenhagen, Denmark. ICES CM 2014/ACOM:30. 115 pages (viewed on 22 October 2018)

ICES (2016) ‘Report of the Joint ICES/OSPAR/HELCOM Working Group on Seabirds (JWGBIRD)’ 9–13 November 2015, Copenhagen, Denmark. ICES CM 2015/ACOM:28. 196 pages (viewed on 23 October 2018)

OSPAR Commission (2017) ‘Intermediate Assessment 2017’ (viewed on 21 September 2018)

Shealer DA, Kress SW (1991) ‘Nocturnal abandonment response to black-crowned night-heron disturbance in a common tern colony’ Colonial Waterbirds, 14, 51-56 (viewed on 23 October 2018)

Acknowledgements

Assessment Metadata

Please contact marinestrategy@defra.gov.uk for metadata information

Recommended reference for this indicator assessment

Ian Mitchell¹, Aonghais Cook⁶, Andrew Douse,² Simon Foster,² Melanie Kershaw,³ Neil McCulloch⁴, Matty Murphy⁵, & Jane Hawkridge¹ 2018. Marine bird breeding success/failure*. UK Marine Online Assessment Tool, available at: /biodiversity-food-webs-and-marine-protected-areas/birds/breeding-successfailure/

* Adapted from OSPAR Intermediate Assessment 2017 on Marine Bird Breeding Success/Failure

¹Joint Nature Conservation Committee

²Scottish Natural Heritage

³Natural England

⁴Department of Environment, Agriculture & Rural Affairs, Northern Ireland

⁵Natural Resources Wales

⁶British Trust for Ornithology