The South Georgia Shag is found only on South Georgia Island (where this species has the greatest population), South Sandwich Island, and the South Orkney Islands (Clements 2014).The islands are located in the Antarctic region of the southern Atlantic Ocean, near to both Argentina and the Antarctic Peninsula. This marine bird is also known as the South Georgia Cormorant and has five other synonymous names: Phalacrocorax georgianus, Notocarbo atriceps georgianus, Notocarbo geogianus, Leucocarbo atriceps georgianus, and Leucocarbo geogianus.The species was described by Einar Lönnberg of Sweden in his book “Contributions to the Fauna of South Georgia” in 1906 (Kennedy and Spencer 2014).Of the order Pelecaniformes, the South Georgia Shag is a member of the Phalacrocoracidae family, containing 39 species of cormorants and shags (Shields 2006).Many researchers use the name Phalacrocorax as the only genus within the Phalacrocoracidae family because of the lack of knowledge of these birds.Others have used Phalacrocorax and Leucocarbo as the two major genera, out of seven total genera, within that family (Kennedy and Spencer 2014).There are also discrepancies over whether or not this is a species or a subspecies of Phalacrocorax atriceps (the Imperial Shag) because it too is a blue-eyed shag (Worthy 2011).
The island and marine habitat of the South Georgia Shag remains cold. The terrestrial portion of their habitat is mostly grassland with inlet waterways.Low-lying coastal regions are the breeding ground for these shags.Near the island there are rock stacks offshore while there are natural barriers due to large glaciers on South Georgia Island itself.These birds forage in coastal waters. In general, all shags have a breeding population of 104-105, are between four and five years old when they first reproduce, have an annual survival rate of 85%, have an average clutch of three, and feed on fish and octopus (Croxall 1987).The benthic fish they tend to eat are thriving (Harris et al. 2014).Although both sexes tend to dive to the bottom of the ocean, males tend to eat fish at slightly higher trophic levels (Bearhop et al. 2006).These bottom divers prefer to eat Notothenia, Trematomus, and Champsocephalus (all genera of Cod Icefishes) that have not yet matured and are found in inshore waters and kelp beds.Because of overfishing, they seem to eat mostly Champsocephalus (Croxall 1987).
South Georgia Shags are known for not using the typical cormorant posture of wing-spreading.Wing-spreading could be for feather maintenance, social display, shading the nest, wing drying, and thermoregulation (Cook and Leblanc 2007).Wing-spreading is probably not exhibited in the South Georgia Shag because the Southern Ocean areas are cold year round.In this climate, avoiding wing-spreading reduces heat loss (Cook and Leblanc 2007).The cost of wing-spreading also outweighs the benefits because these birds are still partially wettable and have little fat to keep them warm, along with notoriously low body temperatures.These traits seem to be adaptations to cold weather conditions (Cook and Leblanc 2007).
ADL, or aerobic dive limit, is the dive duration time at which lactate starts to build up in the blood (Butler 2006).Most dives should not exceed the ADL time limit, but in birds the ADL is normally much less then actual recorded dive durations.However, in blue-eyed shags generally, 36% of their dive durations are greater than the ADL.During diving their already low abdominal temperatures plummet even more (Ponganis and Kooyman 2000).Their common diving duration can be <2 minutes or about 4 minutes (bimodal dive pattern), and their maximum dive duration is around 4.6 minutes.They have a shallow and a deep dive pattern where foraging trips last 6-10 hours (Ponganis and Kooyman 2000).Because of the male-biased sexual size dimorphism, males reach greater depths than the females while foraging (Ponganis and Kooyman 2000)and catch larger prey (Bearhop et al. 2006).
During breeding season, the South Georgia shag uses its energy as efficiently as possible.The energy expenditure during any season is mostly due to buoyancy, depending on the depth of their foraging dives.It was found that a larger depth led to a smaller overall body dynamic, or ODBA (Halsey, Shepard, and Wilson 2011).
An Antarctic Treaty that includes the Agreed Measures for the Conservation of Antarctic Flora and Fauna both preserves and conserves all biotic resources south of -60° latitude.No human can kill, capture, or hurt any native bird in this region without a permit (Croxall 1987).Also, there are waste-disposal methods being used to minimize pollution, regulation of introducing non-native species, and rules prohibiting interference with the birds. SPAs (specially protected areas) and SSSIs (sites of special scientific interest) were also instated to protect the birds.Where there are known populations of the blue-eyed shags in the sub-Antarctic region, there are 5 SPAs and 2 SSSIs.Of the 5 SPAs in this region, 1 is at South Georgia Island (Croxall 1987),and both of the SSIs in the region are written in the range of the South Georgia Shag. Also at South Georgia there are areas of special tourist interest where people can visit, while the rest of the island is completely protected from human activities (Croxall 1987).
Marine reserves are a very good idea as well, but because food resources can move in and out of the normal foraging range for these birds, it is difficult to delineate potential areas for reserves.Overall, conservation priorities for the protection of the South Georgia Shag are: creation of both marine and terrestrial resources, non-native species removal, and research focused on the interaction between the shags and their environment (especially their prey) (Croxall 1987).
The South Georgia Shag is a blue-eyed seabird.They exhibit traits that are similar to those of other members of the cormorant family including long bills, white/black/grey/brown plumage, and webbed feet (Kennedy and Spencer 2014).The average adult weighs 2.5 kg (Croxall 1987).Their plumage is hypothesized to be partially wettable, meaning that part of the plumage is hidden from the air.This is similar to the wettable plumage of cormorants in general. They can fly, so they have partially pneumatic bones.Unlike other cormorants, the South Georgia Shag does not display wing-spreading after diving and foraging (Cook and Leblanc 2007).This species also exhibits sexual size dimorphism (where the males are larger then the females; Wearmouth and Sims 2008).They have generally low abdominal body temperatures as well (Cook and Leblanc 2007).
Current threats to L. georgianus are believed to be habitat disturbance/destruction, predation, and competition for food.They inhabit both marine and terrestrial habitats so they must adapt to problems in both. Humans have introduced many non-native vertebrates to the terrestrial landscape.Non-native herbivores, such as reindeer, goats, and sheep, are degrading and destroying the grassland (Croxall 1987).Reindeer have been killed to restore the South Georgia Island’s native ecosystem (Bazilchuk 2013).Rats, cats, and rabbits were all introduced to the South Georgia Island at some point; only the rats survived long-term.Rats killed the eggs and chicks because they are direct predators of these small birds (Croxall 1987).A non-native rat removal project is in progress to remove rats from the island as well (Bazilchuk 2013).
The biggest conservation issue comes from fisheries.They are exceeding the maximum sustainable yield of prey fish, outcompeting the shags for food.The fisheries take the bottom feeding fish, which have been overexploited, so they are now taking the mid-water fish as well.The South Georgia Shag has a high energy cost for foraging, and they are not good at coping with food shortages, so they are highly susceptible to negative effects due to overexploitation of their food sources by commercial fisheries (Croxall 1987).
