Archived 2020 topic: Audouin’s Gull (Larus audouinii) – reclassify from Least Concern to Vulnerable

Please note: This discussion topic is one of a set about species that are endemic or nearly endemic to the European Union (EU), and whose status in the EU therefore effectively determines their global status. To ensure consistency between the 2020 global and EU Red List assessments of these species, this set of topics is being fast-tracked through BirdLife’s Globally Threatened Bird Forums to inform decisions on the EU (and global) status of relevant species, which must be finalised and communicated to the European Commission by mid-April 2020. Topics on other species will be posted on the Forums shortly, for discussion later in the spring, as per usual. The results of the 2020 global Red List update for birds will be published by IUCN and BirdLife in early December.

Audouin’s Gull Larus audouinii breeds on Mediterranean coasts, with its main breeding areas at the Ebro Delta (NE Spain) and Chafarinas Islands (off NE Morocco), and scattered colonies from Portugal, Morocco and Algeria east to the Aegean Sea, S Turkey and Cyprus; it winters south to Senegambia (Burger et al. 2020). It is currently listed as Least Concern, having been reclassified from Near Threatened in 2015, when its population was considered to be fluctuating (following a huge increase and range expansion) but not declining.

Globally, it has an extremely large extent of occurrence in both the breeding season (>2.2 million km2) and in winter (>8 million km2), and hence does not approach the thresholds for Vulnerable under the range size criteria (B and D2). Its population size is also moderately large, with 43,000–44,000 mature individuals in Europe alone (BirdLife International 2015), and hence does not approach the thresholds for Vulnerable under the population size criteria (C and D1). Therefore, the only potentially relevant criterion is A, which relates to reductions in population size. Until recently, however, its population was not thought to be declining at all, let alone sufficiently rapidly to approach the threshold for listing as Vulnerable under Criterion A (>30% decline over 10 years or three generations, whichever is longer). Consequently, it was evaluated as Least Concern.

In late 2019, all 28 EU Member States were obliged to complete their second 6-yearly report to the European Commission (EC) under Article 12 of the EU Birds Directive, including their latest information on the sizes and trends of the populations and ranges of all naturally occurring wild bird species. Under an EC contract to evaluate the EU population status of each species, BirdLife has now analysed these new data, which indicate that this species’s population has declined significantly in recent years. Specifically, the data reported by Spain (which holds >80% of the European and global population; BirdLife International 2015) suggest that the breeding population declined by 31% in just four years, from 2013 to 2017. No trend was reported by Portugal (11%), and Italy (7%) reported recent stability, but the small populations in France and Greece were also reported as declining.

Further information provided by SEO/BirdLife (J.M. Arcos in litt. 2020) confirms that the Spanish breeding population has in fact been declining since around 2010 (before which time, it fluctuated for several years, as reflected in the current global assessment). The latest version of the Spanish Government’s Marine Strategy for the Levantine coast and Balearic islands (Fig. 11, p. 44) shows that the breeding population peaked at 18,268 pairs in 2006, but had fallen to 10,231 pairs by 2017 (and has declined further since then; J.M. Arcos in litt. 2020). The equivalent Marine Strategy for the Alboran Sea (not currently available online) shows that the breeding population (which includes colonies in Spanish territory on the N African coast, such as Alhucemas, Ceuta and Melilla) also peaked in the mid-1990s at 4,384 breeding pairs, but had fallen to c. 1,900 pairs in 2017 (and has declined further since then; J.M. Arcos in litt. 2020). In total, the Spanish breeding population has declined from 21,264 pairs in 2006 to 12,131 pairs in 2017, and is still declining.

The number of birds breeding at the former main colony (Punta de la Banya) in the Ebro Delta has crashed, from 15,396 pairs in 2006 to 1,355 pairs in 2019 (Genovart et al. 2018; J.M. Arcos in litt. 2020). Some of these birds have relocated and established other colonies elsewhere within the Ebro Delta, including one of 746 pairs, as well as several smaller colonies that together hold up to 4,000 pairs (Oro et al. 2009). However, these recently formed colonies are often in suboptimal areas, such as ports. The main reason for these changes seems to be the presence of predators (e.g. fox, badger) in the Ebro Delta (Payo-Payo et al. 2018), and the lack of suitable nesting places elsewhere, aside from some artificial sites (e.g. ports, saltpans). Fishing moratoria and the reduction of fishing discards off the Ebro Delta may also be an important factor (Cama et al. 2013), although fisheries bycatch is still considered to be a significant threat to the species (Genovart et al. 2017).

The relocation of colonies may be expected in such a nomadic species, and some Spanish breeders are known to have moved to S Portugal (Calado et al. 2018), where numbers peaked at 2,934 pairs in 2018 (2,663 pairs in 2019; J.M. Arcos in litt. 2020). However, this redistribution does not compensate for declines elsewhere, and thousands of birds remain unaccounted for. At a recent meeting of the Spanish Working Group on Audouin’s Gull, attended also by Portuguese and N African experts, the possibility that some of these ‘missing’ birds may have moved to an unknown location(s) in N Africa was discussed (J.M. Arcos in litt. 2020). Morocco was thought unlikely; it was less clear for Algeria.

Notwithstanding this possible redistribution, combining the data currently available from Spain and Portugal (>90% of the global population) suggests an overall decline of around 30% since 2006. The relevant period for assessing trends in this species under Red List Criterion A is 24.3 years (based on an estimated generation length of 8.1 years; Bird et al. 2020). The current population level is about 15% lower than in the mid-1990s, so it does not approach the 30% threshold for listing as Vulnerable under A2 (past declines). However, including data from other countries, and extrapolating the trend observed since 2006 forward three generations (to 2030), implies an overall decline approaching 40%, which falls within the range for qualifying as Vulnerable under A4 (past, present and future declines). Projecting three generations farther into the future under A3 does not seem justified at present, until it is clearer whether the missing birds have relocated somewhere else, and whether the decline at least partly represents a readjustment to a lower and more natural carrying capacity, now that fishery discards have been reduced from the unsustainable levels of the early 2000s (Cama et al. 2013; Genovart et al. 2017).

Overall, this species’s global population appears to be declining at a rate approaching 40% over three generations (24 years), thereby qualifying it for reclassification from Least Concern to Vulnerable under Criterion A4b.

Relevant comments and information on this fast-track topic are welcome by 8 April 2020, please.

Please note that this forum topic is not designed to be a general discussion about the ecology of the species, but rather a discussion of the species’s Red List status. Therefore, please ensure your comments are relevant to the species’s Red List status and the information requested. By submitting a comment, you confirm that you agree to the BirdLife Forums’ Comment Policy.

References

Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., Symes, A., Taylor, J., Şekercioğlu, Ç.H. & Butchart, S.H. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology. https://doi.org/10.1111/cobi.13486

BirdLife International (2015) European Red List of Birds: Audouin’s Gull Larus audouinii.http://datazone.birdlife.org/userfiles/file/Species/erlob/summarypdfs/22694313_larus_audouinii.pdf

Burger, J., Gochfeld, M., Garcia, E.F.J. & Sharpe, C.J. (2020). Audouin’s Gull (Larus audouinii). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. https://www.hbw.com/species/audouins-gull-larus-audouinii

Calado, J.G., Matos, D.M., Ramos, J.A., Moniz, F., Ceia, F.R., Granadeiro, J.P. and Paiva, V.H., (2018) Seasonal and annual differences in the foraging ecology of two gull species breeding in sympatry and their use of fishery discards. Journal of Avian Biology49(1).

Cama, A., Bort, J., Christel, I., Vieites, D.R. and Ferrer, X. (2013) Fishery management has a strong effect on the distribution of Audouin’s Gull. Marine Ecology Progress Series 484: 279-286.

Genovart, M., Doak, D.F., Igual, J.M., Sponza, S., Kralj, J. and Oro, D. (2017) Varying demographic impacts of different fisheries on three Mediterranean seabird species. Global Change Biology 23: 3012-3029.

Genovart, M., Oro, D. and Tenan, S. (2018) Immature survival, fertility and density dependence drive global population dynamics in a long‐lived species. Ecology 99: 2823-2832.

Oro, D., Pérez-Rodríguez, A., Martínez-Vilalta, A., Bertolero, A., Vidal, F. and Genovart, M. (2009) Interference competition in a threatened seabird community: a paradox for a successful conservation. Biological Conservation 142: 1830-1835.

Payo-Payo, A., Sanz-Aguilar, A., Genovart, M., Bertolero, A., Piccardo, J., Camps, D., Ruiz-Olmo, J. and Oro, D. (2018) Predator arrival elicits differential dispersal, change in age structure and reproductive performance in a prey population. Scientific Reports 8: 1-7.

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14 Responses to Archived 2020 topic: Audouin’s Gull (Larus audouinii) – reclassify from Least Concern to Vulnerable

  1. John Croxall says:

    I am/was aware of the concern in SEO over the sudden major change in status. The summary of recent evidence is suficiently compelling to me to warrant the change proposed, but I would entirely defer to the views of those who work on/with this species.

  2. Daniel Oro says:

    I agree with SEO’s proposal. The main concern for the species (and other close protected species with close ecological requirements) is the loss of suitable habitat even within protected areas, where terrestrial predators (mainly carnivores) have increased their populations. By suitable habitat I mean marshes and coastal wetlands, not rocky islands.

  3. Christina Ieronymidou says:

    The small population in Cyprus (15-28 pairs) underwent a decline of c. 37% during 2007 – 2015 (Hellicar 2016), but numbers have since stabilised (BirdLife Cyprus unpublished data). At BirdLife Cyprus we agree with the proposal to uplist the species based on the population trend reported in Spain.

    Hellicar, M. 2016. Rare and localised Audouin’s Gull Larus audouinii declining in Cyprus; results from systematic monitoring 2007–2015 and data for Yellow-legged Gulls Larus michahellis and Mediterranean Shags Gulosus aristotelis desmarestii. Sandgrouse 38: 110 – 117

  4. Borut Rubinić says:

    It seems that in Croatia where the population was first discovered and assessed in 2002 the population trend is more or less stable. Although the micro-locations (breeding rocky islets) change between years (AG is mostly asjusting to the current-yearly distribution of Yellow-legged Gulls), the overall number remains in same range.

    In the 2001 when I did the complete census it was 67 pairs and partial monitoring data suggested that between 1997 and 2002 that number was between 60 and 70 pairs (Rubinić 2002*).

    More current data should be sought by BIOM – BirdLife Croatia, that conducted several projects around AG, Yelkouan and Scopoli’s Shearwater in Croatia recently.

    *Rubinić, B. (2002): Distribution, numbers and breeding ecology of Audouin’s Larus audounii and Yellow-legged Gull L.michahellis on South-Dalmatian islands, Croatia. Bachelor Thesis. University of Ljubljana. Biotechnical Faculty, Department of Biology. Lljubljana. 64 pp.

  5. Nicola Baccetti (ISPRA, Italy) says:

    Italy seems currently split into two different scenarios. A north-western sector – historically holding the whole population – where colonies are now decreasing, changing positions or even disappearing, and a south Tyrrhenian – Ionian (now also Adriatic) sector, where new, large colonies have established. The two patterns may well result in an apparent overall stability of the national stock, although it has to be stressed that there is hardly any exchange of marked individuals between the two areas. For the reasons that the overall number of colonies is small (<20), total breeding failures are frequent, pop trend at least in part of the range is negative and SPA designation of the main Sardinian breeding site is lacking, I'm in favour of the upgrading.

  6. Recorbet Bernard says:

    In France, have only reproduced in Corsica; it is classified as “Endangered” on the national and Corsican IUCN red lists. The Corsican population has always been small (<100 pairs) and fluctuating. The number of colonies fluctuated from 1 to 3 with a significant change; the main colony (located on the islets of Cap Corse) declined sharply from 2000 when a new colony appeared in Aspretto / Ajaccio on a military dike. The trend in the number of pairs has been declining moderately since 2005(about 15-20% ; 2005-2019). The success of reproduction is weak (0,56/pairs) but not against a significant increase but unfortunately concern only the Aspretto colony. We also note a fairly high mortality by accidental capture of amateur fishing. This colony, in urban and artificial site remains very fragile and remains dependent on the contributions of birds born in Sardinia and in Tuscany and the management by the military. On the other hand, exchanges between the Corsican and Spanish colonies are almost zero.
    In conclusion, Corsica remains very marginal and fragile for the conservation of the species with little hope of significant increases in the future.

  7. Sureyya Isfendiyaroglu says:

    Although a new breeding colony of Audouin’s gull was recently discovered in Gokceada (Onmus &Gonulal 2019) at the Northern range of the species distribution, the well established at colony at Aydıncık Islets in Mersin, which is located at the south eastern margin of the species distribution, had declined drastically from 28-30 pairs to 2-5 pairs. This decline had probably resulted from the increasing grazing pressure on the former breeding island (korhan özkan pers. communication.). The breeding colonies in the agean have not been sytematically studied in the last two decades but there’s a decline in the frequency and number of individuals observed around Bodrum and Datca Peninsulas. There’re also increasing anthropogenic activities due to various reasons (factors such as refugee traffic, expanding military operations and constructions) on the islets within the species’ breeding range. It’s evident the species does not have a favorable status around the Turkish coast.

  8. Luka Jurinovic says:

    After the initial assessment of Croatian breeding population in the beginning of 2000’s, we have a gap in knowledge about its size until 2017. In the period of 2017-2019, in Croatia we had 13-45 breeding pairs (13, 43-45 and 30 respectively). With frequent changes of breeding islets, population trend is unknown but it is probably fluctuating or slightly decreasing (Jurinović et all 2019*). Tagging of our birds showed the exchange of individuals between Italian Adriatic colonies, French and Croatian colonies, so population boundaries should be further studied. Breeding success is really low or breeding totally failed (as in 2019) so we are also in favour of the upgrading species status.

    Luka Jurinović and BIOM Life Artina crew

    *Jurinović, L., Zec, M., Dumbović Mazal, V. & Kralj, J. (2019) Explorative GPS-Tracking of Foraging Movements by Audouin’s Gulls Reveals No Association with Fishing Vessels in Croatia. Ardea, 107 (2), 213-221 doi:10.5253/arde.v107i2.a8.

  9. SPEA supports the reclassification of Audouin’s Gull from Least Concern to Vulnerable considering the overall decline of around 30% since 2006.

    Audouin’s Gull is known has a breeder in Portugal since 2001, firstly in the Reserva Natural do Sapal de Castro Marim e Vila Real de Santo António and, a few years later, a second colony was established in the Parque Natural da Ria Formosa, also in a saltpan complex near Tavira, until abandonment in 2007 (Catry et al. 2010). Both colonies were quickly deserted due to high levels of mortality from feral cats and dogs.
    Currently the species only breeds in Ria Formosa Natural Park, specifically at Barreta island (an uninhabited sandy island), and the population is estimated at 2663 breeding pairs in 2019 (Paiva et al. pers. comm.). This colony can be considered as a fragmented subpopulation, given its degree of isolation in relation to the most important breeding colonies located in Spain. Since it was established (in 2008), this colony has increased, reaching the max of 2,934 pairs in 2018 (Paiva et al. pers. comm.). Average annual population growth (2014-2019) has been around 26% and is probably related with species’ dependency of fisheries discards close to key breeding sites, which can become a problem in the future when the Common Fisheries Policy will be fully implemented and the discard ban adopted. Although there are some studies regarding its foraging ecology there is still some information gaps, especially with regards to its population dynamics, annual breeding success, interaction with fisheries, competition with Yellow-legged Gull, predation by invasive mammals or the impacts caused by human disturbance. In 2019, a LIFE project was started (LIFE Ilhas Barreira – LIFE18 NAT/PT/000927), to assess these knowledge gaps and, by the implementation of conservation measures at breeding areas, to improve breeding success and ensure the species long-term survival.

    In 2017, the “European birds of conservation concern: populations, trends and national responsibilities” published by BirdLife considered Audouin’s Gull as Non-SPEC, taking into account the fact that the species was not declining and was overall stable since 2000. In light of this review, we strongly recommend that the SPEC status of the species should be reviewed and updated.

    * Catry, P., Costa, H., Elias, G. & Matias, R. (2010). Aves de Portugal, Ornitologia do Território Continental. Assírio e Alvim, Lisboa. 941 pp.

  10. Danae Portolou & Jakob Fric says:

    In comparison to the large colonies in the western Mediterranean, the Larus audouinii population in Greece has always been relatively small. The species breeds on uninhabited islets, thus habitat availability is considered high, however predation and food availability seem to limit its population size. The Hellenic Ornithological Society (BirdLife Greece) has been monitoring Audouin’s Gulls in the Greek insular area since 1995 through 3 major LIFE Nature projects during which two national censuses were performed in 1998 and 2010. The first national population estimate was 700-900 bp. The second national population census covered 90% of the known breeding distribution and produced an estimate of 350 – 500 pairs, i.e. an apparent decline of approximately 28-33%. Overall, 84 uninhabited islets in 33 breeding regions have been used for nesting, ranging from 1 to 86 breeding pairs. Since 2010, four colonies have been monitored almost annually, and all show significant declines in past population sizes and most importantly almost total breeding failure. In addition, colony fragmentation has been recorded.
    Based on the above, HOS agrees on the proposed upgrading.

    Saravia – Mullin, V., Portolou, D., Evangelidis, A., Gaganis, K., Manolopoulos, A. and J. Fric (2012) The breeding population of Audouin’s Gull Larus audouinii in Greece. In: Yésou, P., Baccetti, N. and J. Sultana (eds). Ecology and Conservation of Mediterranean Seabirds and other bird species under the Barcelona Convention. Update and Progress. Proceedings of the 13th Medmaravis Pan-Mediterranean Symposium, 14-17 October 2011, Alghero, Sardinia, Italy. Medmaravis 2012.

  11. Pep Arcos says:

    The following is a contribution to this forum on behalf of SEO/BirdLife.

    We do support the proposal, given the current situation and following a precautionary approach. The numbers in 2006 were the highest ever, but the decline since then has been sharp, and the trend seems consistent across the last decade. The ongoing reduction of discards (an important food source for the species) and the lack of proper, stable sites for breeding, might extend this decrease into the future, so it is reasonable to raise concern on the species. Proper management of potential breeding sites, including the control of terrestrial predators, and recovery of Mediterranean fish stocks through a careful fishing policy, are likely the most relevant actions to halt this decline.

  12. Red List Team (BirdLife International) says:

    The following comment is posted on behalf of Jula Selmani (National Agency of Protected Areas, Albania:

    Audouin’s Gull, there have been several records of this species along the last years in Albania. There are not yet evidences that the bird is nesting in Albania. However, no monitoring of the suitable habitats has been carried out yet. Therefore, as a breeder, considering the small area of occupancy (equal to suitable habitat to breed in Albania) the species should be classified as “EN” under the B criteria (B2). In addition, if it breeds in Albania, we estimate that it should have a small population less than 250 mature individuals, thus, it classifies as “CR” under the criteria “C” and likewise “EN” under the criteria “D”.
    The status of the species in Albania we estimate to be “EN”.

  13. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion over the past 10 days. We realise that the window for consultation was short (and is now closed), and greatly appreciate the time and effort invested by so many people in commenting, especially during this unprecedented time globally. The volume and variety of responses received on this (and other) species means that it will take us several more days to digest, analyse and interpret everything. We will however do so as quickly as possible, posting our considered conclusions on this species’s status on this page in a final contribution by mid-April.

    Thank you once again, and Happy Easter.

    BirdLife Red List Team

  14. Red List Team (BirdLife International) says:

    Following careful review and consideration of the existing available information, as well as the new information and valuable views shared through the consultation above, we have now reached a decision on the status of this species for both the 2020 global Red List and the EU Red List of birds. Our conclusion is that this species should be classified as Vulnerable (A3bce+4abce) – representing a reclassification from its current status of Least Concern, to reflect its recent and ongoing decline.

    Many thanks once again to everyone who contributed to the discussion above and helped to inform this outcome. The 2020 Red List update for birds including this assessment will be published on the BirdLife and IUCN websites in December.

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