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Status Assessment 2022 - Iberian guillemot

The status of the Iberian guillemot Uria aalge albionis is very poor, the breeding population has probably already disappeared. The real causes for the population decimation still prevail, especially incidental by-catch in fishing gears. A recovery of the population in the future is very unlikely.

Assessment of threats

Incidental by-catch

Oil pollution

Food limitations

Climate change

Egg collection, shooting

Threat or impact







Assessment of statusBreeding DistributionNon-breeding distributionBreeding population sizeNon-breeding population sizeCondition, reproductive successCondition, habitat qualityPrevious OSPAR status assessmentStatus (overall assessment)

I       NA
II       NA
III       NA
V       NA

Explanation to table:

Distribution, Population size, Condition

Trends in status (since the assessment in the background document)

↓     decreasing trend or deterioration of the criterion assessed
↑     increasing trend or improvement in the criterion assessed
←→     no change observed in the criterion assessed
trend unknown in the criterion assessed

Previous status assessment: If in QSR 2010 then enter Regions where species occurs ( ○) and has been recognised by OSPAR to be threatened and/or declining (● ) based on Chapter 10 Table 10.1 and Table 10.2 . If a more recent status assessment is available, then enter ‘poor’/’good’

Status*(overall assessment)

red – poor
green – good
? – status unknown
NA- Not Applicable
*applied to assessments of status of the feature or of a criterion, as defined by the assessment values used in the QSR 2023 or by expert judgement.


Key Pressure

↓    key pressures and human activities reducing
↑    key pressures and human activities increasing
←→     no change in key pressures and human activities
? Change in pressure and human activities uncertain

Threats or impacts (overall assessment)

red – significant threat or impact;
green–no evidence of a significant threat or impact
Blue cells – insufficient information available
NA – not applicable



1 – direct data driven
2 – indirect data driven
3 – third party assessment, close-geographic match
4 – third party assessment, partial-geographic match  
5 – expert judgement



Background Information

Year added to OSPAR list: 2003

The original evaluation of the Iberian guillemot Uria aalge albionis against the Texel-Faial criteria referred to global importance, decline and sensitivity criteria, with information also provided on threat.

  • Global/regional importance: at the time of listing (2003) the entire breeding population of the Iberian guillemot was only found in the Wider Atlantic (Region IV) of the OSPAR Maritime Area, apparently isolated from other breeding populations.
  • Decline: the Iberian guillemot has dramatically declined since its inclusion in the OSPAR List of threatened and/or declining species and habitats, and at the last assessment the species was thought to be virtually extinct as a breeding seabird in Iberia (OSPAR 2013).
  • Sensitivity: originally listed as sensitive due to the small breeding population and restricted breeding area. This subspecies was considered to be particularly sensitive to incidental by-catch in fishing nets and oil pollution.
  • Anthropogenic pressures and biological factors: in the past human removal of eggs and shooting of adults at sea may have had considerable impact. Latterly oil pollution and mostly incidental by-catch in fishing nets have been identified as main causes of population crash. Climate change effects on prey availability have not been demonstrated.

Last status assessment: 2013. OSPAR (2013) concluded that the species as breeder was virtually extinct in Region IV and continued to qualify under the OSPAR Texel-Faial criteria due to its marked population decline, small population size, limited number of breeding localities, uncontrolled threats, and inadequate conservation measures. This situation has been corroborated by the current assessment.

Geographical Range and Distribution

The common guillemot Uria aalge (Pontoppidan 1763) has a complicated taxonomy with five subspecies currently accepted distributed on both sides of the North Atlantic and Pacific oceans. The subspecies albionis breeds in Ireland, South Britain, Helgoland, Brittany and West Iberia, and is therefore the subspecies breeding in Region IV. Subspecies ibericus suggested by Salomonsen (1935) and supported by Bernis (1948) is not currently accepted.

The geographical breeding range of the Iberian guillemot has been in steady decline since the 1950s. There is no information available on the winter distribution of the Iberian guillemot, but the species Uria aalge is common all over the North-East Atlantic Ocean throughout winter.

Method of assessment: 3a- Source: OSPAR background information and monitoring programs in Spain and Portugal.


Figure 1: a) OSPAR regions. Region IV where the Iberian guillemot Uria aalge albionis occurs is shaded. b) The breeding distribution of the Iberian guillemot in the Iberian Peninsula. Red squares enclose the breeding area in Galicia and the Berlengas islands. Cape São Vicente, where the species also bred, is shown by a red dot.

Figure 1: a) OSPAR regions. Region IV where the Iberian guillemot Uria aalge albionis occurs is shaded. b) The breeding distribution of the Iberian guillemot in the Iberian Peninsula. Red squares enclose the breeding area in Galicia and the Berlengas islands. Cape São Vicente, where the species also bred, is shown by a red dot.


The global population of the subspecies albionis is estimated at ca. 300 000 birds by the European Environment Agency (EEA indet.) and shows an overall positive trend in the long term. This is not the case for the subspecies in OSPAR Region IV, where the guillemot is now probably extinct as a breeding seabird species. The species was common in the Berlengas islands (Portugal) where 6 000 breeding pairs were estimated in 1939 and on the Galician coast (Spain) in the 1940-1960 period (about 1 500 breeding pairs), but all the populations dropped dramatically from the 1960s onwards and at present all the breeding colonies have disappeared. The last breeding event in Portugal (Berlenga island) involving 17 birds was recorded in 2002, and the last single Iberian guillemot was observed here in 2014 (Lecoq 2003, Morais et al 2003, Oliveira et al 2016). In Spain the last breeding event was recorded for the colony of cape Vilán (Galicia) in 2007, when two pairs were observed attending two chicks, although some adults were later observed in the colony still in 2012 and 2013 (two and three birds, respectively) (Barros 2021). 

Method of assessment: 2a -. Source: national surveys and monitoring programs in Spain and Portugal and unpublished own data (this report).


Information on the breeding ecology of the Iberian guillemot Uria aalge albionis is scarce. Apart from occasional observations, there are no data on the breeding success of the different colonies. The breeding habitat of the Iberian guillemot, inaccessible sea-cliffs and partially submerged caves at cliff bases (locally named as furnas), has not changed since the time when the species was abundant. On the contrary, in the last decades the feeding habitat related to the breeding colonies has been eroded by oil pollution and an increased fishing effort on the part of local fisheries.

Method of assessment: 3b – Source: current literature, OSPAR 2013

Threats and Impacts

Between 1960 and 1974 the Iberian guillemot Uria aalge albionis suffered an annual decline of 33,3%. Pollution, changes in prey availability, incidental by-catch mortality in fishing nets and climate change have been suggested as the main causes for the dramatic decline in the species. The collapse of the Iberian guillemot population was specifically analysed by Munilla et al (2007). These authors did not detect a decrease in the availability of the likely prey (pelagic fish). Furthermore, climatic conditions were good during the worst period of the Iberian guillemot decline, and a possible effect of climate change on the availability of main prey has not been demonstrated. Regarding human activities, the rapid development of gillnet fisheries appears as the main factor underpinning the population crash. Pollution derived from large oil spills could have contributed to the extinction of the species. 

Measures that address key pressures from human activities or conserve the species/habitat

The Iberian guillemot is listed in Annex 1 of the EU Birds Directive (2009/147/EC).

The Iberian guillemot breeding population was categorised as endangered in the Spanish Catalogue of Threatened Species (Royal Decree 139/2011, 4February 2011). This decree establishes the obligation of regular monitoring (every three years) of endangered species.

The Iberian guillemot was listed as an endangered species at a regional level (Galicia) by Decree of 19 April 2007 (Decree 88/2007 19 April).

In Portugal, the common guillemot is considered a priority species under the Berlengas SPA management recommendations.

OSPAR Recommendation 2014/2016 on furthering the protection and conservation of the Iberian guillemot (Uria aalge) in Region IV of the OSPAR Maritime Area includes the introduction of legislation to improve the protection of the species, the declaration of new marine protected areas, the study of key negative impacts on the population (specifically by-catch in fishing gears and oil spills) and the implementation of measures in order to reduce them, and finally a regular monitoring of the remaining population. In the last 15 years the Iberian guillemot has been benefited from some regional and national legislation (see this section, above*), and its last breeding colonies were one of the main reasons for the declaration of the Special Protection Area ES0000176 Costa da Morte (Norte); moreover, the marine habitats surrounding this colony are protected by Special Protection Area ES0000497 Espacio Marino de la Costa da Morte, created by Order AAA/1260/2014, of 9 July 2014. In addition, this SPA has been included in the OSPAR Marine Protected Areas (MPA) Network. Regarding main impacts on the population, despite recommendations no specific measures have ever fully been implemented. Finally, the Galician regional government has recently commissioned a review of the status of the species (Munilla, 2017), although the Iberian guillemot is extinct as a breeder since about a decade.

Conclusion (including management considerations)

The new available data confirm the highly negative trend identified in the last assessment for the species, which considered the Iberian guillemot Uria aalge albionis as virtually extinct (OSPAR 2013). The last observation of Iberian guillemots in a suitable breeding habitat and season occurred in Spain in 2013 (three birds in Cape Vilán). In Portugal, the last of the Iberian guillemots was observed in the cliffs of Berlenga island in 2014. Since then, no new records of Iberian guillemots in the known colonies have been made, despite specific and intensive monitoring. At the time of writing, the species has been completely absent from its breeding quarters in Portugal for the past seven years and in Spain for the past eight years. Although the period of time since the last confirmed breeding events is perhaps too short to consider the Iberian guillemot as officially extinct, new breeding attempts are increasingly unlikely to happen. Confidence in the current status assessment is high due to the quantity of information available for the previous years.

The main threats having caused the decrease in Iberian guillemot population numbers are still present and have even increased over the last decades. This is especially true for the incidental by-catch in fishing nets, which has turned the Atlantic Iberian waters into a hostile habitat for many seabird species. Although incidental by-catch in fishing nets is likely to have had an important negative effect on the population of the Iberian guillemot, actions to reduce this impact have never been implemented

Although the common guillemot Uria aalge (including the subspecies albionis) is a common species in Iberian Atlantic waters outside the breeding season and particularly in winter, there are no reasons to expect the breeding population to recover, at least not in the short term. The closest colonies to Iberia are found in Brittany (France) and have remained stable for the last years, while some of the smaller colonies have also disappeared, but a rapid increase in numbers have been recorded in 2019-2020 (Cadiou et al 2021). Moreover, the Iberian guillemot marked the southern limit in the breeding distribution of the species in the Atlantic, and under current climate change the edges in the distribution of North Atlantic species are expected to move northwards, and not to the south (Hampe & Petit 2005).

Knowledge gaps

There is very little information regarding past distribution, population size, trends and biology of the Iberian guillemot Uria aalge albionis. This is especially true for the first decades following on from the discovery of the main populations. It is evident that now that the species seems to have disappeared, it is impossible to obtain new information and any future research on the species must be based on older and scarce data, or information from other populations. Another considerable gap when analysing the trend of the Iberian guillemot in Spain, even in the last few decades, is the scarcity of accurate censuses available, and the lack of periodicity between them.

Method used

Main source of information:

3. Assessment derived from a mix of OSPAR data assessment and assessments from third parties

Assessment is based upon:

b)    mainly extrapolation from a limited amount of data. Trends are inevitably estimative due to the scarcity of censuses available, particularly in Spain; some ecological parameters are inferred from other populations due to the lack of accurate information. Overall published information about the Iberian guillemot is scarce, and there is just one scientific paper investigating the causes of the population crash. Compared to the background document (OSPAR 2013), the present status assessment is significantly improved by the inclusion of new data on population size, trends and ecological aspects of the species.

Barros , A. (2021). Arao común, Uria aalge. En: López-Giménez, N. (Ed.). Libro Rojo de las Aves de España. SEO/BirdLife. Madrid.

Bernis, F. (1948). Las aves de las Islas Sisargas en junio. Boletín de la Real Sociedad Española de Historia Natural 46: 647–648.

Cadiou B., Jacob Y., Provost P., Quénot F., Février Y. (2021). Bilan de la saison de reproduction des oiseaux marins en Bretagne en 2020. Rapport de l’Observatoire régional des oiseaux marins en Bretagne, Brest, 37 p. 

EEA (indet.). Uria aalge albionis. Assessment of the status at the European level. Report under the Article 12 of the Birds Directive.

Hampe, A., Petit, R.J. (2005). Conserving biodiversity under climate change: the rear edge matters. Ecology Letters 8: 461-467.

Lecoq, M. (2003). Censo das Populações de Aves Marinhas Nidificantes no Arquipélago das Berlengas em 2002: Calonectris diomedea, Phalacrocorax aristotelis e Uria aalge. Relatório II (Final): Censo da População em 2002. SPEA. Unpublished report.

Morais L., Crisóstomo, P., Santos, C. (2003). Contagen de aves marinhas nidificantes na Ilha Berlenga Larus cachinnans, Phalacrocorax aristotelis e Uria aalge. Actualidade e dados historicos. ICN Reserva Natural das Berlengas. Unpublished report.

Munilla, I., Díez, C., Velando, A. (2007). Are edge bird populations doomed to extinction? A retrospective analysis of the common guillemot collapse in Iberia. Biological Conservation 137: 359–371.

Munilla, I. 2017. Monitoring and conservation assessment of the breeding populations of the European shag (Phalacrocorax aristotelis), the Cory’s shearwater (Calonectris diomedea), the Common guillemot (Uria aalge) and the Black-legged kittiwake (Rissa tridactyla) in Galicia. Consellería de Medio Ambiente e Ordenación do Territorio, Xunta de Galicia. Unpublished report.

Oliveira, N., Almeida, A., Santos Torres, A., Fagundes, I., Rodrigues, P., Andrade, J. (2016). Updated Information on the Breeding Status of Berlengas Archipelago Seabirds. Report of the Action A1, Project LIFE Berlengas. SPEA - Portuguese Society for the Study of Birds, Lisbon. Unpublished report.

OSPAR (2013). Background Documento for Iberian guillemot (Uria aalge). OSPAR Commission, 2013.

Salomonsen, F. (1935). Aves. In S.L. Tuxen et al. (eds.): The zoology of the Faroes. Vol. 3. Part 2. Copenhagen: A.F. Høst & Søn.


Audit trail

Sheet reference:

BDC 2022/Iberian guillemot Uria aalge albionis