The black-browed (Thalassarche melanophrys) and Atlantic yellow-nosed (Thalassarche chlororhynchos) albatrosses and the white-chinned petrel (Procellaria aequinoctialis) are the seabird species most frequently captured by pelagic longline fisheries in the southwest Atlantic. This study estimates this type of bycatch and describes the spatial-temporal patterns of the incidental capture of these species by the Uruguayan pelagic longline fleet, based on data collected by scientific observers on 47 fishing trips from 2004 to 2007. Three generalized linear models (GLM) models were employed to predict bycatch for each species based on the observed data. We also developed a spatio-temporal species-specific analysis. Captures were recorded in Uruguayan waters, mainly over the slope and depth waters, and in international waters adjacent to Uruguay, the north of Argentina, and the south of Brazil. The highest catch rates for black-browed albatrosses and white-chinned petrels were recorded on the Uruguayan slope from fall to spring, while the highest values for Atlantic yellow-nosed albatrosses were recorded further to the north, in the international waters off Brazil in late winter. The average estimated number of black-browed and Atlantic yellow-nosed albatrosses and white-chinned petrels caught during the study period was 1683, 257 and 239 birds, respectively. Taking into account the total effort of the fleet, these values represent an estimated catch rate of 0.276, 0.042, and 0.039 birds/1000 hooks for these species, respectively. The results of the present study suggest that the annual impact of this fishery is medium to high on the black-browed albatross, low on the Atlantic yellow-nosed albatross and low on the white-chinned petrel. However, the situation of these species in the southwest Atlantic should be viewed with considerable concern, as our understanding of the impact of the bycatch on their populations requires more research. Any effort to reduce seabird mortality in the southern hemisphere should target this geographic region.

Solidified stomach oil deposits in snow petrel colonies in the Antarctic proved to be suitable for 14C dating and provide important palaeobiogeographical and palaeoenvironmental information. Following earlier studies in the Untersee oasis (Central Dronning Maud Land) we present here 14C measurements on comparable deposits from the Bunger Hills (66°10′S, 101°E). The conventional 14C age of the basal layer reflects the occupation age of any particular nesting site and therefore a minimum age for the time when this area became ice-free. According to the 14C results the occupation of the southern part of the Bunger Hills by petrels started about 10000yr ago. The breeding colonies expanded continuously following local ice retreat. The most intensive phases of colonization seem to have been from 8–6 kyr BP and during the past 2 kyr.

Sanctioned longline fishing for Patagonian toothfish around the Prince Edward Islands (a globally important seabird breeding site) commenced in 1996 following high levels of Illegal, Unregulated and Unreported (IUU) fishing. Independent fishery observers accompanied all but two sanctioned trips between 1996 and 2000, allowing a thorough understanding of the impact of this fishery on seabirds. Overall, white-chinned petrels Procellaria aequinoctialis were by far the most frequently killed species. However, during the first year, when lines were set during the day and night, a significant number of albatrosses (particularly grey-headed albatrosses Thalassarche chrysostoma) were also killed. Birds were caught almost exclusively during their breeding seasons and most birds killed were breeding adult males from the Prince Edward Islands. Albatrosses and giant petrels were caught almost exclusively during day sets, whereas catch rates of white-chinned petrels did not differ between day and night sets. Albatrosses were caught closer to the islands than white-chinned petrels. Most white-chinned petrel carcasses were hooked in their wings and bodies, whereas albatrosses were caught most frequently in their bills and contained large numbers of baits. Rates of seabird bycatch in the sanctioned fishery decreased from 0.19 birds per 1000 hooks to 0.034 birds per 1000 hooks during the time of this study. This was probably mainly due to stricter implementation of mitigation measures and a progressive movement farther away from the islands over the years. We estimate that the combined impact of legal and IUU longline fishing around the Prince Edward Islands over the past four years could have resulted in between 7000 and 17 000 seabird mortalities and could have had significant impacts on the breeding populations of several seabird species breeding on the Prince Edward Islands. This was mainly due to high levels of IUU fishing during 1996/97.

Sexual size dimorphism in the Cape petrel Daption capense was analysed to improve methods for sexing live birds in field studies. Samples originated from two geographically distant study populations in the Antarctic: Nelson Island, South Shetland Islands (sample N: 83 M, 89 F), and Ardery and O'Connor Islands, Windmill Islands (sample A: 36 M, 27 F). Using single characters with cut points calculated from sexed individuals, about 59–76% (N; best separator tarsus length) and 61–86% (A; best separator tube length) of birds could be assigned to the correct sex. Combination of characters improved performance of sample-specific discriminant functions to a maximum of 84% in the N-sample (five characters) and 95% in the A-sample (four characters). The most useful character sets as well as ranking of individual characters (their weights) differed between samples. At the same time, cross-testing revealed asymmetry in the applicability of sample-specific functions to the other sample. Hence, the method of a generalized discriminant (Auk110: 492–502, 1993) was implemented and tested to develop a species-specific discriminant for the Cape petrel. For all examined character sets, results of their cross-application to the other sample were improved by using character weights estimated from combined samples instead of weights derived only from the original sample. The generalized function (tube length + 1.05*bill depth at tube + 0.72*culmen length + 0.07*wing length) combined with a cut point calculated from a distribution of discriminant scores (assumed mixture of two normal distributions with possibly unequal variances) is suggested as currently the best compromise for sexing Cape petrels in populations for which specific functions are not yet available: comparison with our best sample-specific functions shows a decrease in accuracy by only 1% to 3%. However, examination of other promising characters (head length, bill depth at gonys, mid-toe length) is recommended to improve further a generalized discriminant. In all cases a larger percentage (N: 87–89%, 38 pairs; A: 100%, 27 pairs) of individuals was correctly sexed by within-pair comparison of discriminant scores than according to the sample-specific cut point. No clear evidence for assortative mating with respect to body size has been found in this study. Available biometric data show little evidence for geographical variation in the Cape petrel, which suggests good applicability of generalized sex-discriminants in other populations.

The diet of the brown skua (Catharacta skua lönnbergi) was studied at Mayes Island, Kerguelen archipelago, by collection of prey remains on 11 territories during the complete breeding cycle of the species there. In nine territories, collections were daily or every two days for a quantitative investigation of the diet. The blue petrel (Halobaena caerulea) and thin-billed prion (Pachyptila belcheri) accounted for, respectively, 72.9 and 19% of the remains. Differences in diet and prey capture rate were analysed according to territory size, local abundance of prey inferred from the vegetation cover of territories, colony attendance patterns of prey, and according to the breeding timing and success of skuas. Skuas holding large territories caught more prey, and especially more blue petrels than those with small territories. Diet reflected local abundance of blue petrel and thin-billed prion but the blue petrel was apparently preferred to other available prey. Failure to breed was not significantly related to hunting performance of the skua or to food availability, but sample size was small. Variations over time of prey capture rates reflected the colony attendance patterns of the main prey. Captures of blue petrel and thin-billed prion were most numerous during their respective laying, incubation and hatching periods, decreasing during chick-rearing. Prey capture rates were greatest when brown skuas were hatching, and decreased during chick-rearing to a minimum when young skuas were fledged. Capture rate patterns differed according to laying date of skuas: early breeding skuas caught more prey and were well synchronized with the breeding cycle of the blue petrel and late breeders exhibited more dependence on the thin-billed prion for some periods. Finally, this study has allowed us to assess the impact of the brown skuas upon the burrowing petrels on this locality.