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Rock Shag Phalacrocorax magellanicus

This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Taxonomic source(s)
SACC. 2006. A classification of the bird species of South America. Available at:
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

Distribution and population
The Rock Shag breeds on the southern coasts of Argentina and Chile, including Tierra del Fuego and the Falkland Islands (Islas Malvinas). It can be found wintering as far north as Uraguay6.

Trend justification
The population trend is difficult to determine because of uncertainty over the extent of threats to the species.

Behaviour The Rock Shag is a foot-propelled pursuit diver widely distributed in southern South America. It generally forages within 5 km of the colony, and eats a variety of primarily benthic prey. It principally forages during daylight hours, with occasional night time trips during moonlit nights when birds forage in similar locations and depths as during the day (Sapoznikow and Quintana 2002). It forages solitarily, in strictly coastal areas, and feeds at the sea bed (Punta et al. 1993). Diet At Punta Loma, Argentina, the main prey are benthic fish Riberoclinus eigenmant and the polychaete Eunice sp., both associated with sandy seafloors and seaweeds (Quintana 2001). At Bahias Bustamante and at Melo, Argentina, the species fed mainly on Rock Cod (Notothenia spp.), which were present in 87% of breeding and 91% of non-breeding regurgitated pellets (Punta et al. 1993). Foraging range At Punta Loma, Argentina, during the chick-rearing period, birds spent 36% of daylight hours away from the colony on feeding trips, and 92% of the foraging trip was spent diving (Quintana 2001). Shags fed mainly in water less than 10m deep, with a gravelly sand bottom and within 5 km of the shore (Quintana 2001). The mean foraging ranges were 3.8 ± 2.6 km and 2.6 ± 2.3 km in 1996 and 1997 respectively (Quintana 2001). These results are consistent with observations made in Bahia Bustamante, Argentina, where the observed foraging range was between 50-2000 m from the coast (Punta et al. 1993). Typically, the species forages in inshore waters less than 20m deep (Quintana 1999). Using a published relationship between dive depth and dive duration in Shags (depth (m) = (dive time (s)-35)/1.28), the mean diving depth for Rock Shags was estimated at 12.7 ± 7.5 m, with 86% of dives under 20 m (Quintana 1999). In Port Stanley Harbour, Falklands, birds foraged mainly in or just outside giant kelp beds (Macrocystis spp. and Lessonia spp.), within 50 m of shore and where the water was 1-6 m deep (Wanless and Harris 1991). Fewer birds foraged up to 100 m out, in water 7-13 m deep but not over kelp beds (Wanless and Harris 1991). The mean water depth for dives was 4.5 m (Wanless and Harris 1991). At Bahia Bustamante and Melo, Argentina, birds either foraged within bays, or else at a distance of less than 200 m from the shore and among kelp (Macrocystis pyrifera) beds (Punta et al. 1993). They foraged in areas which were 2 - 12 m deep, and contained algae (Punta et al. 1993). Foraging occurred at the bottom throughout the year, but occasionally also in mid-water during the breeding season (Punta et al. 1993). At Punta Loma, Argentina, the seabed in all the foraging areas consisted of bands of shallowly-sloping, gravelly sand sediments, with tuffs and wave cut platforms in some areas (Quintana 2001). The features of the seabed at foraging sites were consistent with the habitat requirements of the principal prey species, i.e. sandy sea floors and seaweeds (Quintana 2001). Shags used the same feeding areas during the two study years (Quintana 2001).

del Hoyo, J.; Elliot, A.; Sargatal, J. 1992. Handbook of the Birds of the World, vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain.

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Punta, G., Saravia, J. and Yorio, P. 1993. The diet and foraging behavior of two Patagonian cormorants. Marine Ornithology 21: 27–36.

Quintana F. 1999. Diving behavior of Rock Shags at a Patagonian colony of Argentina . Waterbirds 22(3): 466-471.

Quintana F. 2001. Foraging behaviour and feeding locations of Rock Shags Phalacrocorax magellanicus from a colony in Patagonia, Argentina . Ibis 143(4): 547-553.

Sapoznikow, A., Quintana, F. 2002. Evidence for Rock Shags Phalacrocorax magellanicus and Imperial Cormorants P. atriceps leaving their nests at night. Marine Ornithology 30(1): 34-35.

Wanless, S., & Harris, M. P. 1991. Diving patterns of full-grown and juvenile rock shags. Condor 93: 44-48.

Text account compilers
Hatchett, J., Calvert, R., Butchart, S., Ekstrom, J.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Phalacrocorax magellanicus. Downloaded from on 12/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from on 12/07/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Rock shag (Phalacrocorax magellanicus) 0

Key facts
Current IUCN Red List category Least Concern
Family Phalacrocoracidae (Cormorants)
Species name author (Gmelin, 1789)
Population size mature individuals
Population trend Unknown
Distribution size (breeding/resident) 467,000 km2
Country endemic? No
Links to further information
- Additional Information on this species