
Mediterranean Shag (Phalacrocorax aristotelis desmarestii). Credit: Constantine Alexander. All rights reserved
The Mediterranean Shag (Phalacrocorax aristotelis desmarestii) is an endearing but reclusive marine bird that inhabits southern Europe and southwest Asia principally along Mediterranean coasts and, to a lesser extent, the Black Sea coast. It is one of three subspecies of the European Shag (Phalacrocorax aristotelis) which is noted for being among the deepest divers in the cormorant family capable of reaching depths to 45 metres in search of its preferred fish and other mid-water as well as benthic community prey. The other two subspecies are P. aristotelis aristotelis which inhabits northwest Europe along the Atlantic coast and P. aristotelis riggenbachi which resides along the northwestern African coast.
The Mediterranean Sea, which is situated at the crossroads of Europe, Africa and Asia, has been described in Latin as mare medi terraneum - the “sea in the middle of land”. The sea occupies a 2,509,559 square kilometre surface area with an average depth of 1,460 metres and a maximum depth of 5,267 metres. The sea’s coastline extends 46,000 kilometres through 22 countries. The Mediterranean Sea has a restricted interchange with the Atlantic Ocean through the Strait of Gibraltar on the west and the Black Sea through the Strait of Dardanelles and the Sea of Marmara to the east. Although the Mediterranean Sea covers only 1% of the world’s marine areas, it hosts 6% of the world’s marine species. It is to this region that the Mediterranean Shag is endemic and contributes to the natural beauty, rich biodiversity and remarkable productivity of the region’s extraordinary coastal and marine environment.
Description:
As an excellent swimmer and diver, the Mediterranean Shag is a robust, medium to large size marine bird measuring approximately 70-80 centimetres in length with an expansive 95-110 centimetre wingspan. The streamlined Shag has dark feathers, a long narrow bill, pale coloured cheeks on its face and a long curved neck. Its strong feet are designed to facilitate its propulsion through the water when diving and foraging in coastal waters. The Mediterranean Shag is easily distinguishable by its curved crown tuft of feathers during breeding season.
Distribution:
Mediterranean Shags prefer an undisturbed natural environment along rocky coasts and islands adjacent to clear water inhabited by their preferred prey of fish and other mid-water and benthic marine organisms. Mediterranean Shags are usually never far from land and can be found roosting on isolated rocks and boulders along the shore. The reclusive shags can also be seen swimming and diving along the coast, often alone and away from human activities. These habitats can be found along their geographical distribution range which includes Spain, Gibraltar (UK), France, Italy, Greece, Slovenia, Croatia, Bulgaria, Albania, Ukraine, Turkey, Algeria, Libya, Tunisia, Cyprus and Egypt where the entire global population of the Mediterranean Shag is estimated to be fewer than 10,000 breeding pairs.
Approximately one half of the global population breeds in the European Union (EU), especially along the coasts of Spain, Baleares, Corsica, Sardinia, Tuscany archipelago, Lampedusa as well as Ionian and Aegean sea islands and islets. Countries which have recently had among the highest estimated Mediterranean Shag populations include Croatia, Italy, Turkey, Spain, France and Greece.
There have been very significant fluctuations in breeding numbers from year to year in several Mediterranean colonies which, along with the reclusive behaviour of the bird, have contributed to the difficulty in estimating the population with the desired degree of reasonable accuracy; however, according to the 2002 Mediterranean Shag Species Action Plan for the Convention on the Conservation of European Wildlife and Natural Habitats by BirdLife International for the European Commission, the global population was estimated to be fewer than 10,000 pairs shortly after the turn of the century. By 2011, Mediterranean Shag experts were in agreement that the subspecies population had declined largely as a result of human activities that adversely impact their breeding, foraging and roosting behaviour.
At a higher taxonomic level, the International Union for Conservation of Nature acknowledged in its 2009 assessment that the “population trend appears to be decreasing” as well for the European Shag (Phalacrocorax aristotelis) species to which the Mediterranean Shag subspecies belongs, although the European Shag was not then considered threatened at a global level.
Diet and Foraging:
With its proficiency as a foot-propelled pursuit diver, the Mediterranean Shag forages in mid-water or along the bottom of sandy and rocky sea beds and shows a preference for sheltered fishing grounds such as bays and channels, although it generally avoids estuaries, shallow or muddy inlets and fresh or brackish waters. The Mediterranean Shag usually forages alone when away from nesting colonies and during winter, but a dense shoal of fish may attract a small flock of Mediterranean shags in search of essential nutrition.
The Mediterranean Shag diet consists primarily of coastal fish species and marine benthic organisms. For example, according to one 2011 report of a Mediterranean Shag study conducted off the Croatian coast and in the Gulf of Trieste, post-breeding Mediterranean Shags in the Gulf preyed on fish species largely from the demersal and relatively immobile Goby (Gobiidae) family, such as the dimunitive Black Goby (Gobius niger) that usually reaches 10 centimetres (cm) in length. During the breeding season the Shags exhibited a more varied diet including more mobile benthic-pelagic prey such as the Brown Comer (Serranus hepatus) that usually reaches 15 cm and is found over seagrass, sand, mud and rocks; and the Peacock or Painted Wrasse (Crenilabrus tinca) that averages 25-30 cm in length and lives up to 14 years; and the schooling Big Scale Sand Smelt (Atherina boyeri) that is small, usually 7-10 cm in length. In addition, the Mediterranean Shag diet also includes other species from the Labridae family of wrasses; the Ammodytidae family of sand lances including small sandeels which burrow into the sand; and, to a lesser extent, polychaetes (segmented, or bristled, worms), cephalopods, other molluscs, and small benthic crustaceans.
The Mediterranean Shag can often be seen swimming alone along the coast during the cold months of winter, during which time most tourists and residents are absent from the seashore and refrain from recreational marine activities such as boating. The bird can be distinguished from other cormorant species as it makes a slight upward movement with the upper half of its body allowing it to stretch before it arches its head and neck as a prelude to diving into the water to feed on the fish or other marine prey that can be found midway in shallow coastal water or along the bottom of rocky or sandy sea beds. Ornithologists have always stressed the important contribution of healthy seagrasses to the reproduction and population sustainability of fish and other marine organisms that are a staple food source for the Mediterranean Shag.
Reproduction:
During the winter breeding season, Mediterranean Shags form sparse colonies and nest in rocky crevices, ledges, caves within sea cliffs or in between boulders. Their nesting dates vary from year to year depending on the region and its conditions. The nests, which are constructed of a variety of marine vegetation and other plant materials, are usually situated within a few metres above the high water level, but they have been recorded at altitudes reaching and even exceeding 100 metres.
If the nests remain in good condition, they are often reused during successive seasons. The younger birds of breeding age nest later than the older, mature birds; therefore, the younger birds are left to occupy nest sites that are not as desirable or advantageous as their more mature counterparts. As a result, the younger birds experience a lower rate of breeding success. The egg-laying period frequently varies from year to year depending on the region, but this period usually occurs between December and March. During each breeding season, Mediterranean Shags do not exhibit synchronized breeding dates among the various colonies within their distribution range, or among colonies within a given region or even among individuals within the same colony. This lack of synchronisation is attributed to the different experience levels among the breeding birds, the different geographic locations of the colonies and the variety of weather conditions that pervade the colonies. At egg-laying, the birds usually produce a clutch of 3 eggs which are incubated for 30 days prior to hatching. The post-hatching period during which the chicks develop to a fully grown state lasts approximately 53 days, at which point the offspring are usually ready to fledge.
During the breeding season, the geographical radius from the colony in which the Mediterranean Shags conduct their foraging and other maintenance activities generally extends to 15 kilometres. At the end of the breeding season, the adults as well as the juveniles disperse over a wide area, which in some cases may reach or even exceed 200 kilometres according to ornithological ring recoveries, whereupon the Mediterranean Shags use more remote foraging grounds. At that time, small feeding and roosting groups are formed.
Threats:
Mediterranean Shags are subject to the same threats to which other marine birds are exposed, the most notable of which are:
- mortality as a result of accidental capture (bycatch) in fishing gear such as gill nets and fish traps, particularly when the gear is permanently located close to the shore;
- the destruction by trawlers of Posidonia seagrass meadows (Posidonia oceanica) and biogenic reefs that facilitate fish reproduction on which the Mediterranean Shags rely;
- the serious depletion of fish stocks through overfishing by Mediterranean fisheries, many of which participate in illegal and, to a very large extent, unreported fishing. This fish stock depletion is especially detrimental to Mediterranean Shags which prey on many fish species that are unsustainably over-harvested by these fisheries;
- Coastal development and coastal recreational activities that result in significant disturbances as well as habitat loss, fragmentation and degradation which adversely impact the birds’ foraging, roosting and breeding behaviour. Among the activities which represent some of the most serious threats to the Mediterranean Shags are tourism; motorised marine recreation including jet skis and speedboats; the construction of ports, marinas and sea walls; coastal commercial and residential development; and sand extraction for beach regeneration which can severely damage Posidonia seagrass beds and other benthic (marine seabed) communities on which the Mediterranean Shags feed and rely for their survival;
- uncontrolled boat anchoring that destroys seafloor habitats, such as seagrass meadows, which facilitate fish reproduction on which the birds rely; and
- toxic marine contaminants, such as organochlorines and mercury, from sources including land runoff, industrial discharges, oil spills and illegal ship tank washing which have permeated the various levels of the marine food chain in the widely contaminated Mediterranean Sea region and result in lethal as well as sub-lethal health consequences to Mediterranean Shag adults, chicks and eggs.
Additional threats to the Mediterranean Shag include:
- direct persecution by fisheries and fish farm operators as the birds are shot, intentionally drowned and poisoned because they are perceived to be a threat to fish stocks;
- illegal shooting of Mediterranean Shag vagrants to Malta from pleasure boats that sail from Malta to the Pelagian Islands of Italy and from Maltese fishing boats that target adults and recently fledged juveniles, according to the July 2002 Species Action Plan for Mediterranean Shags for the Convention on the Conservation of European Wildlife and Natural Habitats;
- direct hunting of adults and chicks as well as egg collection for food;
- unlawful beach sand extraction by private contractors for building construction in the Mediterranean region;
- the presence of dogs;
- predation of eggs and nestlings by black rats (Rattus rattus) and Yellow-legged gulls (Larus michahellis) in certain locations such as Aegean Sea islands and islets; and
- livestock grazing and the presence of black rats that reduce vegetation cover which serves to shelter nesting sites, and this, in turn, reduces the availability of suitable breeding habitats.
Mortality from Fisheries:
Independent from fisheries reports, bird ringing recoveries reveal that more than 40% of the recorded mortality of the Mediterranean Shag is associated with fishing activities, including recreational fishing from the coast and the combined deployment of gill nets and trammel nets.
The combined use of gill nets and trammel nets consists of bottom-set gear comprised of 2 parts: the upper part is a standard gill net which is designed to catch fish by their gills and is maintained vertically by floats on the floatline and weights on the ground line, and the lower part of the combination is a trammel net where bottom fish become entangled. The combined fishing gear produces a high rate of accidental capture (bycatch) of diving seabirds, such as Mediterranean Shags, as they become caught at various levels of the water column and are drowned.
Drag Racing with Mediterranean Shags:
“The moral progress of a civilisation can be measured by the way it treats its animals.”
Mohandas Karamchand Ghandi (also known as Mahatma Ghandi, 1869-1948), political and ideological leader of India.
A unique threat to marine birds with which certain Mediterranean Shag populations are faced is derived from resident speed boats that engage in the recreational pursuit of Mediterranean Shags. Incidents of “drag racing” with Mediterranean Shags have been reported in the Greek Dodecanese islands, despite the legal protection afforded to the species under the European Union Birds Directive (79/409/EEC) which remains largely unenforced in Greek as well as other southern European waters.
One example of such a report was filed on Tilos Island by two visitors from Germany on 8 March 2007 at the Hellenic Port Authority and the office of the 2004-2008 European Union (EU) Tilos Island LIFE Nature Project which was established for the benefit of the Mediterranean Shag and 2 other avian species. According to the reports based on witness and “drag racing” boat participants’ statements, island residents in speed boats chase the birds that fly low over the surface of the water prompting the birds to initiate a myriad of defensive manoeuvres in an effort to escape potential harm from the boats’ rapidly-approaching pursuits. This unlawful activity, for which no action was ever undertaken by the local Hellenic Port Authority in spite of the complaints delivered to the office concerning this unlawful behaviour, causes the progressive weakening and consequential inability of the birds to sustain evasive action. Witnesses to the March 2007 incident reported the fatality of the legally protected Mediterranean Shag, which became exhausted, disappeared below the surface and failed to resurface, simply for the fleeting entertainment of the Tilos Island residents.
In the absence of Hellenic public sector enforcement of the EU Birds Directive provisions, this recreational past-time along with other anthropogenic threats to the species’ conservation status contributes to the continuing Mediterranean Shag population decline in which certain stakeholders regrettably appear to be disinterested and about which experts continue to be justifiably concerned.
Legal Protection:
Valid concerns about the declining Mediterranean Shag population prompted the inclusion of this European Shag subspecies in various laws and conventions related to its status and protection, including:
- European Union Birds Directive (79/409/EEC), Annex I;
- a listing for the Mediterranean population of the Phalacrocorax aristotelis species in the Bern Convention on the Conservation of European Wildlife and Natural Habitats, Appendix II;
- Barcelona Convention Protocol Concerning Specially Protected Areas and Biological Diversity in the Mediterranean, Annex II which provides a List of Endangered or Threatened Species;
- Bulgarian Nature Conservation Act of 1962 and 1986 national legislation (amended in 1997) relating to punitive measures for acts resulting in injuries to or the death of individuals of the species. Also, the Bulgarian Red Data Book, listed under “Threatened Species”;
- Hunting Law of Tunisia;
- Terrestrial Hunting Law of Turkey; and
- Ukrainian Red Data Book, Category II.

Mediterranean Shag (Phalacrocorax aristotelis desmarestii). Credit: Constantine Alexander. All rights reserved
Contact: Constantine Alexander