Foods of the south polar skua Catharacta maccormicki in the eastern Larsemann Hills,Princess Elizabeth Land,East Antarctica

Regurgitated pellets and food remains were collected near nest sites, and from a club site, of south polar skuas Catharacta maccormicki in the eastern Larsemann Hills, Princess Elizabeth Land, East Antarctica, during the skuas' presence in the area. The samples indicated that the snow petrel Pagodroma nivea, the most abundant seabird species breeding locally, formed the major dietary component, comprising some 66% of food items identified in pellets and 80% of the food remains obtained. Adélie penguins Pygoscelis adeliae (which do not breed in the Larsemann Hills), other seabirds, fish and marine foods were rarely found as remains or in pellets. However, refuse (meat, fish and vegetable remains) taken as food by skuas from nearby stations occurred in pellets at all sites and formed about 12% of the food remains collected and identified. In this study, foods taken by skuas were related both to the local breeding distribution of snow petrels, and to the possession of a feeding territory. Birds without feeding territories took somewhat fewer snow petrels and included more refuse from local stations in their diet, as did those at the club site. Future monitoring of the influence of anthropogenic foods (and inedible waste materials) on the species' ecology is considered important.     

Trophic interactions between brown and south polar skuas at Deception Island,Antarctica

It is broadly accepted that the brown skua (Stercorarius antarcticus lonnbergi) competitively excludes the south polar skua (S. maccormicki) from penguin colonies when breeding sympatrically, forcing the latter to feed on marine resources. The purpose of this work was to examine the diets and trophic niche breadths of each species where they co-occur and to determine the degree of overlap. To this end, we analyzed 169 pellets of brown skuas, collected in two different areas (20 individuals), and 152 of south polar skuas, collected in three different areas (18 individuals), on Deception Island, South Shetland Islands, Antarctica, during the austral summer 2000. Pellet analysis often underestimates the amount of easily digestible prey, but allows for comparisons of the relative contributions of different items in the diet. South polar skuas at our study locations consumed seven different food items and had a trophic niche breadth of 0.133 compared to brown skuas that fed on 10 different items and had a trophic niche breadth of 0.078. The niche overlap between the species was 82.1%. Penguins were the principal food source of both species, however, brown skuas fed mostly on chicks, while south polar skuas fed on adults (carcasses). The use of different age classes of penguins as a food source offers an alternative to competitive exclusion, allowing the coexistence of these species on Deception Island.     

Foods of the South Polar skua Catharacta maccormicki at Ardery Island, Windmill Islands, Antarctica

South Polar skuas (Catharacta maccormicki) breed on Ardery Island in the absence of a local breeding population of Adelie penguins (Pygoscelis adeliae). Assessment was made of the food remains in skua feeding territories in 1995/1996. The diet of South Polar skuas largely consisted of fulmarine petrel species which bred on Ardery Island. Southern fulmar (Fulmarus glacialoides) remains were the predominant prey items found, and skuas appeared to feed preferentially on this species. Accepted: 3 June 2000     

PREY SELECTION AND TEMPORAL VARIATION IN THE DIET OF SUBANTARCTIC SKUAS AT INACCESSIBLE ISLAND,TRISTAN DA CUNHA

Ryan, P.G., & Moloney, C.L. 1991. Prey selection and temporal variation in the diet of Subantarctic Skuas at Inaccessible Island, Tristan da Cunha. Ostrich 62:52-58.

More than 2 500 prey items of Subantarctic Skuas Cuthuructa anturcricu were identified from regurgitated pellets collected at a roost of non-breeding skuas during summer 1989–90 at West Point, Inaccessible'Is-land. Most prey items (96,5%) were birds, primarily burrow-nesting procellariiforms. Sixteen bird species were recorfed in the diet, but five secies accounted for 94,6% of identifiable prey remains: Whitebellied Storm Petrel Fieettu grullariu (53,5%), Whitefaced Storm Petrel Pelugodrorna marina 15,1%), Broad-billed Prion Pacaptilu vittutu (14,0%), Great Shearwater Puffinus gruvis (7,3%), and Iommon Diving Petrel Pelecunoids urinutrix (4,7%). Petrel chicks were important in the diet, particularly Great Shearwaters. The main non-avian prey were fish and goose barnacles Lepas sp., but their importance may have been underestimated. The remains of a rat Rattus sp. presumably were derived from the neighbouring island of Tristan da Cunha; rats are not known to occur on Inaccessible Island. Prey size affected seabird availability to skuas, and dietary composition vaned throughout the summer in relation to seabird breeding cycles. Both these factors reduce the value of skua diet as an indicator of the relative abundances of burrow-nesting petrels. There was no correlation between skua diet and estimates of breeding bird abundance, but this may be a consequence of studying non-breeding skuas. Subantarctic Skua diet in 1989–90 was similar to that recorded in previous years, with consistent seasonal trends between years.     

Foods of the south polar skua at Hop Island,Rauer Group,East Antarctica

Summary Pellets regurgitated by south polar skuas at Hop Island, in the Rauer Group, East Antarctica, Princess Elizabeth Land were collected and analysed. Individual collections were grouped in relation to the nearest breeding colony of seabirds, but irrespective of their source the frequencies of occurrence of the food items identified in pellets indicated that Adélie penguins were of varying, but major (29%–72%), importance to skuas inhabiting the Island. Though the incidence of Antarctic petrel remains (from adult or chick) was generally low in pellets (<7%), the occurrence of remains of southern fulmars was high (>27%) at all sites near the fulmar breeding colonies. Fish remains, and beaks of cephalopods, were present in few pellets. Whilst indicating the range of foods eaten on Hop Island, and perhaps their relative importance, it is considered that the pellets by themselves do not reflect accurately the level of predation of eggs of Antarctic petrels and southern fulmars, nor do the pellets necessarily include the remains of young of these species.     

Diet,individual specialisation and breeding of brown skuas (<Emphasis Type="Italic">Catharacta antarctica lonnbergi</Emphasis>): an investigation using stable isotopes

The diet of brown skuas (Catharacta antarctica lonnbergi) on Bird Island, South Georgia was assessed using a combination of stable isotope analysis (SIA) and mixing model techniques. We found evidence that individual specialisation in diet of adult brown skuas was related to timing of breeding, which may reflect differences in intrinsic quality. Adults with more enriched ¹³C values hatched chicks earlier than those with depleted ¹³C values. Individuals with enriched ¹³C fed predominantly on Antarctic fur seal (Arctocephalus gazella) carrion and placenta while those with lower ratios appeared to rely more on burrowing petrels (e.g. Antarctic prions Pachyptila desolata). Individual foraging differences clearly influenced timing of breeding and potentially the reproductive output of breeding pairs. We confirmed that the main components of the diet of brown skuas during incubation are, in decreasing order of importance, Antarctic fur seal placenta, burrowing petrels and fur seal muscle. In addition, we identified fur seal faeces in the diet during this stage, which had not been detected previously by traditional sampling methods. Finally we identified a correlation in δ¹³C values between pair members, attributable to the influence of courtship feeding of females by males, or assortative mating according to foraging preference or intrinsic quality.     

118 A Nutritional Analysis of the Turf Algal Diet and Fecal Pellets of The Green Turtle,Chelonia Mydas L

In 1978, the green turtle, Chelonia mydas, was listed as threatened in the United States under the Endangered Species Act. Any knowledge gained from an understanding of the diet and how it affects this species' ability to survive is crucial. Turf algae, the primary component of the diet of Chelonia mydas, and turtle fecal pellets were collected from Kaloko‐Honokohau National Historical Park on the island of Hawaii at monthly intervals. The turf algae and fecal pellets were subjected to nutritional analyses for protein, carbohydrate, lipid, ash, and caloric content. The fecal pellets were higher in protein content than the turf algae, which may be related to fermentation carried out by bacteria in the turtle hindgut that increases the amount of protein available for absorption. From the nutritional data, assimilation efficiencies were calculated for the green turtle.     

Effects of time and rainfall on PCR success using DNA extracted from deer fecal pellets

Non-invasive wildlife research using DNA from feces has become increasingly popular. Recent studies have attempted to solve problems associated with recovering DNA from feces by investigating the influence of factors such as season, diet, collection method, preservation method, extraction protocol, and time. To our knowledge, studies of this nature have not addressed DNA degradation over time in wet environments, and have not been performed on fecal pellets of ungulates. Therefore, our objective was to determine the length of time a fecal pellet from a Sitka black-tailed deer (Odocoileus hemionus sitkensis) could remain in the field in a temperate rainforest environment before the DNA became too degraded for individual identification. Pellets were extracted from the rectum of recently killed deer and placed in an environment protected from rainfall and in an environment exposed to rainfall. Pellets from each treatment group were sampled at intervals of 2, 7, 14, 21, and 28 days after deer harvest. DNA was extracted from sampled pellets and individual samples were genotyped using microsatellite markers. Amplification failure and errors (dropout and false alleles) were recorded to determine extent of DNA degradation. Eighty percent of samples in the protected environment and 22% of samples in the exposed environment were successfully genotyped during the 28-day experiment. With no samples being successfully genotyped in the exposed environment after 7 days, our study showed that rainfall significantly increases degradation rates of DNA from ungulate pellets.     

Long-term changes in population size,distribution and productivity of skuas (<Emphasis Type="Italic">Stercorarius</Emphasis> spp.) at Signy Island,South Orkney Islands

In this study, we investigate the numbers, productivity and territory distribution of the two species of skuas (brown Stercorarius lonnbergi and south polar Stercorarius maccormicki) breeding at Signy Island, South Orkneys, and compare the results with trends elsewhere. Comparison with previous counts indicates a biphasic increase in brown skuas at Signy Island; much faster from 1958/1959 to 1982/1983 (3.3 % per annum), than in subsequent years (0.4 % per annum from 1983/1984 to 2013/2014). Relative distribution of territories has changed little over time. The reduced rate of population growth in recent years was broadly coincident with a decrease in numbers of penguins (and therefore potential prey), which may also explain recent reductions in skua numbers at other Antarctic sites. As prey have become limiting, breeding success of brown skuas at Signy Island is now slightly lower than in the 1950s/early 1960s, but timing of breeding does not appear to have changed. Brown skuas at Signy Island may still have enough resources to start breeding, but as the season progresses and availability of resources declines, chick survival is reduced. South polar skuas have declined from ten pairs in 1982/1983 to one pair in 2013/2014, and mixed pairs have increased from one to three pairs. A review of the literature indicated that although population trend data are available for relatively few sites elsewhere in the subantarctic and Antarctic, numbers of brown skuas appear to be generally decreasing or stable, and of south polar skuas to be stable or increasing.     

Hybridisation between South polar skua (Catharacta maccormicki) and Brown skua (C. antarctica lonnbergi) in the Antarctic Peninsula region

Hybridisation between South polar skua (C. maccormicki) and Brown skua (C. antarctica lonnbergi) in the area of the Antarctic Peninsula is known at least since the beginning of the last century but no survey has been done so far. This paper reviews information on the species composition of skua colonies of more than 10 pairs in the Antarctic Peninsula region, and the incidence of mixed pairs. Morphometrics, population size and breeding success were examined in detail at King George Island. The northward distribution of South polar skuas extended to King George Island (62°11′ S 59°00′ W), with a small outlying population on Signy Island (60°45′ S 45°36′ W), whereas Brown skuas did not breed further south than Anvers Island archipelago (64°46′ S 64°03′ W). The proportion of mixed pairs was highest at the northern end of the ∼500-km-wide hybrid zone. Body size distribution of sympatric skuas from King George Island is clearly bimodal but overlaps considerably and hybrids cannot be identified. Skua population sizes at Potter Peninsula/King George Island remained stable between 1994 and 2004. Numbers of mixed breeding pairs fluctuated more strongly than those of pure species pairs. Breeding success of Brown skuas varied the least.     

Genetic variation in Antarctic populations of the moss Sarconeurum glaciale

Sixty-six isolates of the moss Sarconeurum glaciale were collected from sites in continental Antarctica at Ross Island, southern Victoria Land and the Vestfold Hills. Genetic variation within and among the populations was estimated using isozymes and random amplified polymorphic DNA (RAPD) technology. Isozyme results only reproducibly showed variation between the populations with one enzyme; RAPDs indicated significantly higher levels of genetic variability within and among the Vestfold Hills samples than in the Ross Sea region samples. A dendrogram produced from the RAPD bands suggested that the Ross Island and southern Victoria Land samples form one population, and those from the Vestfold Hills form a separate and more variable population, possibly resulting from separate colonisation events on the continent. Received: 15 March 1996 / Accepted: 1 May 1997     

Diet and long-term changes in population size and productivity of brown skuas <Emphasis Type="Italic">Catharacta antarctica lonnbergi</Emphasis> at Bird Island,South Georgia

Breeding ecology of brown skuas (Catharacta antarctica lonnbergi) was studied at Bird Island, South Georgia in the austral summers of 2000/2001–2003/2004. A complete census recorded 467 breeding pairs in 3.55 km² of suitable habitat (132 pairs per km²), and an additional 312 nonbreeders at club-sites. Comparison with previous counts indicates two phases of population change: an initial rapid increase (3.6% per annum) from the late 1950s to early 1980s, probably attributable to increased carrion availability from the expanding Antarctic fur seal (Arctocephalus gazella) population, followed by slower growth (0.9% p.a.). Currently, seal carrion dominates the diet of skuas during incubation, with a switch to seabird prey during chick-rearing. Breeding is now later, chick growth poorer, and productivity significantly lower than in the early 1980s. There is also a strong seasonal decline in adult attendance, and chicks that hatch later and are in poorer condition are less likely to fledge. These results suggest a long-term increase in competition for carrion that is particularly apparent once fur seal pupping has ceased.     

Aspects of the foraging behaviour of the Antarctic Tern Sterna vittata gaini at Harmony Point, South Shetland Islands

During January and February of 2002 and 2003, we studied the diet of the Antarctic Tern Sterna vittata gaini at two colonies in Nelson Island, South Shetland Islands, by identifying the prey fed to chicks by breeders. The fish Notothenia coriiceps was the main prey in both seasons, followed by the myctophid Electrona antarctica, Antarctic krill Euphausia superba and gammarid amphipods. The contribution of fish to the diet increased as chicks grew older. Fish and amphipods were brought to chicks during the day, whereas adults brought Antarctic krill at sunrise and sunset. Both the duration of the feeding trips and the number of trips per foraging bout varied according to the type of prey caught. Preliminary information suggests that, among other causes, the foraging strategy is strongly influenced by the predation pressure of skuas on chicks. Results are compared with the only two previous study on the diet of the Antarctic Tern at the South Shetland Islands.     

Behavioural ecology of lonnbergi skuas in relation to environment on the Chatham Islands,New Zealand

Abstract

A population of lonnbergi skuas (family Stercorariidae) was studied over December and January 1974–75 on Rangatira Island, Chatham group (44°22′S,176°11′W). The main aim was to compare the behavioural ecology of these birds with that of maccormicki skuas of Antarctica, and to assess the moderating effect of environment on habits. The skuas held extensive territories along the coast and in inland areas clear of forest and bracken. Five of the 11 study territories were occupied by trios of adult birds. A major effect of the vegetation was to reduce contact between neighbours on the ground at territorial boundaries, and most territorial defence was by aerial display and attack. Eggs were laid from late September, and chicks began flying in late December and January. This breeding schedule is about 2 months earlier than for lonnbergi at Signy Island or for skuas in Antarctica, but falls on a trend line of latitude against egg-laying when all populations are considered. Seventeen chicks were reared on the 11 territories, a breeding success of 1.55 chicks per nest. This high success rate was attributable largely to success in rearing both chicks when two were hatched. This is seldom achieved in more extreme climates, and is apparently determined by the intensity of sibling competitiveness. It is hypothesised that this intensity is graded, and aggression by the older chick of the pair is provoked more easily by food shortage as environmental conditions become increasingly severe. The most important prey items recorded were adult petrels, especially broad-billed prion (Pachyptila vittata vittata) and white-faced storm petrel (Pelagodroma marina maoriana) captured on the ground at night. The skuas were mostly inactive during the day, and were not seen to fish or to chase or harass any other bird on or about the island. Southern blue penguins (Eudyptula minor minor), though very common on the island, were not attacked by the skuas. Skuas were not seen to attempt to dig out petrel or penguin nesting burrows. Of the differences in ecology recorded, only the presence of three adults on territories appears to be characteristic of lonnbergi; it has not been recorded for maccormicki or hamiltoni, and is either unknown or very rare in skua.     

THE DIET AND IMPLICATIONS OF DIETARY CHANGE OF CAPE GANNETS ON BIRD ISLAND,ALGOA BAY

Batchelor, A. L. & Ross, G. J. B. 1984. The diet and implications of dietary change of Cape Gannets on Bird Island, Algoa Bay. Ostrich 55:45-63.

The diet of the Cape Gannet Sula capensis breeding on Bird Island, Algoa Bay, South Africa, was investigated. Approximately 2000 regurgitations representing 13300 prey items were examined. Twenty-three teleost and two cephalopod species were recorded in the diet. More than 90 % of the numerical composition consisted of the three species Pilchard Sardinops ocellata, Anchovy Engraulis capensis and Saury Scomberesox saurus. The proportions of these three species in the diet changed during the sampling periods. These changes were not related to the implied migration patterns of these species. Chick growth rates were investigated in conjunction with the dietary study. These results indicated that Cape Gannet chicks on a diet of Pilchard and/or Anchovy were more likely to fledge successfully than those on a diet of Stockfish Merluccius capensis or Saury. These observations were based on differences in growth rate, and peak and fledgling mass, The data suggest that Pilchard is a preferred prey species and its presence or absence in regurgitationsMayreflect a similar situation on the feeding grounds. The observed increase in the Bird Island gannet populationMaybe related to the availability of high-quality food and consequent reduced pre-breeding mortality. In the absence of historical dietary data, further detailed population dynamics studies are required to support this supposition.     

ASSESSMENT OF POTENTIAL BIAS WITH SNOWSHOE HARE FECAL PELLET-PLOT COUNTS

Abstract: The fecal pellet-plot method has been used extensively for snowshoe hare (Lepus americanus) population studies across the species' range, but potential biases associated with the technique have not been addressed adequately. We studied hare pellet-plots in northern Idaho to quantify pellet decomposition rates across environmental gradients, and conducted feeding trials on captive hares to assess the role of diet on pellet production rates. We found that across our study area pellet numbers tended to be higher on plots with high vegetative cover, which likely was a reflection of hare habitat choice rather than lesser pellet decomposition in such habitat. A pellet decomposition experiment indicated that pellet persistence was negatively related to moisture level, and that pellets produced by hares during summer decomposed more quickly than those from winter. We found that only 19% of fecal pellets collected from plots located across northern Idaho were produced by hares during winter. There was a correlation between pellet numbers from plots that were pre-cleared 1 year earlier and estimated numbers of hares on 6 study areas. A similar correlation was lacking for pellet counts from uncleared plots, implying that hare population estimation via pellet-plot counts should involve plot pre-clearing. In captive studies, juvenile hares produced slightly fewer pellets per day per gram of food ingested than adults, but pellet production was similar across diets comprised of 10 different browse species. We conclude that for our study area the fecal pellet-plot method may be subject to notable pellet decomposition bias, and therefore recommend that use of the method elsewhere across the species' range be preceded by assessment of both the pellet-hare density relationship and pellet decomposition rates across habitats.     

Food habits of Metachirus nudicaudatus (Didelphimorphia,Didelphidae) in a Brazilian Cerrado: diet composition and dietary seasonality

The diet of the brown four-eyed opossum (Metachirus nudicaudatus) at a riparian savanna in Brazil was analyzed using 22 fecal samples collected monthly from November 2009 to October 2011. A comparison was established between samples from rainy and dry seasons. Diet composition varied seasonally. Arthropods and fruits were consumed in different frequencies of occurrence, in both seasons, but small vertebrates were only found in the dry season. Diet differences among biomes (Atlantic Forest and Cerrado) were also assessed by comparing the frequency of food items in the fecal sample in our study with data from the literature. Invertebrates (100%) were the most frequent food category found, followed by fruits (59%) and vertebrates (13.6%). Small differences in the consumption of invertebrates were found among the biomes. Nevertheless, seed frequency was significantly higher in samples from the Cerrado than in those from the Atlantic Forest. In our study site, Metachirus nudicaudatus is opportunistic and has an omnivorous diet, tending to include more fruits in its natural diet than has been previously described.     

Bacterial Colonization on Fecal Pellets of Harpacticoid Copepods and on Their Diatom Food

Fecal pellets make up a significant fraction of the global flux of organic matter in oceans, and the associated bacterial communities in particular are a potential food source for marine organisms. However, these communities remain largely unknown. In the present study, the bacterial communities on fecal pellets of the benthic copepod Paramphiascella fulvofasciata feeding on the diatoms Navicula phyllepta and Seminavis robusta were analyzed. The aim of this study was to characterize the bacterial communities associated with the diatoms and the fecal pellets by means of DGGE profiling. Furthermore, isolated bacteria were characterized by means of partial 16S rRNA gene sequencing. The composition of the bacterial microflora on fecal pellets was studied in terms of the effect of the original food source, the age of the fecal pellets and the copepod’s identity. Alphaproteobacteria, Flavobacteria, and Bacilli were found on the fecal pellets; whereas on diatoms, exclusively Gammaproteobacteria were identified. Especially after eating N. phyllepta, there was an important increase in bacterial diversity, although the diatom N. phyllepta harbored a less diverse bacterial community than S. robusta. Our data suggest that the additional bacteria originate from the copepod’s digestive tract and largely depends on the initial food source.     

Gastrointestinal Bacteria of Certain Antarctic Birds and Mammals

An investigation was carried out of the aerobic gram-negative intestinal flora of 158 penguins, 30 skuas, and 66 seals from the Antarctic and sub-Antarctic zones and Phillip Island. Among penguins and seals, 17% and 11%, respectively, were devoid of aerobic enteric organisms, but microscopic examination showed the presence of other bacteria. The coliforms outnumbered the paracolons and nonlactosefermenting bacteria; irregular coliform types and Escherichia coli were predominant. The present study indicated the effect of diet on the composition of the intestinal flora of the birds and mammals examined.     

Estimating abundance of Sitka black-tailed deer using DNA from fecal pellets

Densely vegetated environments have hindered collection of basic population parameters on forest-dwelling ungulates. Our objective was to develop a mark–recapture technique that used DNA from fecal pellets to overcome constraints associated with estimating abundance of ungulates in landscapes where direct observation is difficult. We tested our technique on Sitka black-tailed deer (Odocoileus hemionus sitkensis) in the temperate coastal rainforest of Southeast Alaska. During 2006–2008, we sampled fecal pellets of deer along trail transects in 3 intensively logged watersheds on Prince of Wales Island, Alaska. We extracted DNA from the surface of fecal pellets and used microsatellite markers to identify individual deer. With genotypes of individual deer, we estimated abundance of deer with moderate precision (±20%) using mark–recapture models. Combining all study sites, we identified a 30% (SE = 5.1%) decline in abundance during our 3-year study, which we attributed to 3 consecutive severe winters. We determined that deer densities in managed land logged >30 years ago (7 deer/km², SE = 1.3) supported fewer deer compared to both managed land logged <30 years ago (10 deer/km², SE = 1.5) and unmanaged land (12 deer/km², SE = 1.4). Our study provides the first estimates of abundance (based on individually identified deer) for Sitka black-tailed deer and the first estimates of abundance of an unenclosed ungulate population using DNA from fecal pellets. Our tool enables managers to accurately and precisely estimate the abundance of deer in densely vegetated habitats using a non-invasive approach. © 2011 The Wildlife Society.