Search

The wandering albatross, Diomedea exulans, is a globally threatened species breeding at a number of sites within the Southern Ocean. Across the South Georgia archipelago, there are differences in population trends even at closely located colonies. Between 1999 and 2018 the largest colony, at Bird Island, declined at 3.01% per annum, while in the Bay of Isles, the decline was 1.44% per annum. Using mean demographic rates from a 31-year study at Bird Island and an 11-year study of breeding success at Prion Island in the Bay of Isles in a VORTEX model, we show that differences in breeding success do not fully explain observed differences in population trends. Other potential contributing factors are differential use of foraging areas, with possible knock-on effects on adult body condition, provisioning rate and breeding success, or on bycatch rates of adults or immatures. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is an environmental contaminant which, at high concentrations, can negatively influence avian physiology and demography. Albatrosses (Diomedeidae) have higher Hg burdens than all other avian families. Here, we measure total Hg (THg) concentrations of body feathers from adult grey-headed albatrosses (Thalassarche chrysostoma) at South Georgia. Specifically, we (i) analyse temporal trends at South Georgia (1989–2013) and make comparisons with other breeding populations; (ii) identify factors driving variation in THg concentrations and (iii) examine relationships with breeding success. Mean ± s.d. feather THg concentrations were 13.0 ± 8.0 µg g−1 dw, which represents a threefold increase over the past 25 years at South Georgia and is the highest recorded in the Thalassarche genus. Foraging habitat, inferred from stable isotope ratios of carbon (δ13C), significantly influenced THg concentrations—feathers moulted in Antarctic waters had far lower THg concentrations than those moulted in subantarctic or subtropical waters. THg concentrations also increased with trophic level (δ15N), reflecting the biomagnification process. There was limited support for the influence of sex, age and previous breeding outcome on feather THg concentrations. However, in males, Hg exposure was correlated with breeding outcome—failed birds had significantly higher feather THg concentrations than successful birds. These results provide key insights into the drivers and consequences of Hg exposure in this globally important albatross population. [ABSTRACT FROM AUTHOR]

Invasive species present a major conservation threat globally and nowhere are their affects more pronounced than in island ecosystems. Determining how native island populations respond demographically to invasive species can provide information to mitigate the negative effects of invasive species. Using 20 years of mark-recapture data from three sympatric species of albatrosses (black-browed Thalassarche melanophris, grey-headed T. chrysostoma, and light-mantled albatrosses Phoebetria palpebrata), we quantified the influence of invasive European rabbits Oryctolagus cuniculus and extreme weather patterns on breeding probability and success. Temporal variability in rabbit density explained 33–76% of the variability in breeding probability for all three species, with severe decreases in breeding probability observed after a lag period following highest rabbit numbers. For black-browed albatrosses, the combination of extreme rainfall and high rabbit density explained 33% of total trait variability and dramatically reduced breeding success. We showed that invasive rabbits and extreme weather events reduce reproductive output in albatrosses and that eliminating rabbits had a positive effect on albatross reproduction. This illustrates how active animal management at a local breeding site can result in positive population outcomes even for wide ranging animals like albatrosses where influencing vital rates during their at-sea migrations is more challenging. [ABSTRACT FROM AUTHOR]

Prions Pachyptila are the most abundant seabirds in the Southern Ocean and comprise two main groups: those with and without bill lamellae to filter zooplankton. With few exceptions, each breeding location supports at most one species from each of these groups. However, Gough Island supports two morphologically very similar, filter-feeding species: broad-billed P. vittata and MacGillivray's prions P. macgillivrayi. To understand how these two species co-occur in sympatry, we compared the foraging ranges, habitat selectivity, trophic segregation and moult schedules of these species using combined geolocation-immersion loggers. After breeding, both species showed a well-defined westward migration prior to moulting. Moult lasted 11–19 weeks and was significantly longer in MacGillivray's than broad-billed prions. Moulting birds occurred in specific areas within the Argentine Basin, with little overlap between the two species. Habitat analysis revealed species-specific preferences, in particular sea surface temperature. Activity patterns also differed; MacGillivray's prions spent more time in flight, which indicates a more active foraging strategy, relying less on filter feeding. Stable isotope ratios (δ15N) in flight feathers were greater in MacGillivray's prion, which is consistent with its less specialized bill morphology resulting in feeding at a higher trophic level. Inter-specific spatial segregation was observed for most of the tracking period, in large part because broad-billed prions breed roughly 3 months earlier than MacGillivray's prions. At Tristan da Cunha, 250 km farther north, where only broad-billed prions breed, they departed, moulted and returned significantly later (15–17 days) than conspecifics from Gough Island, providing evidence for character displacement in sympatry with MacGillivray's prion. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We describe the migration routes and non-breeding areas of Common Terns (Sterna hirundo) from the Azores Archipelago, based on ringing (banding) recoveries and tracking of three birds using geolocators. Over 20 years, there have been 55 transatlantic recoveries of Common Terns from the Azores population: six from Argentina and 49 from Brazil. The three tracked birds migrated south in different months (August, September, November), but the northern migration was more synchronous, with all leaving in April. The birds were tracked to three areas of the South American coast: the male spent November-April on the northern Brazilian coast (13°N-2°S), whereas the two females first spent some time off central-eastern Brazil (4-16°S; one for 1 week, the other for 3 months) and then moved south to the coast of south-eastern Brazil, Uruguay and northern Argentina (24-39°S). Although caution is needed given the small sample size and errors associated with geolocation, the three tracked terns potentially travelled a total of ~23 200 km to and returning from their non-breeding areas, representing an average movement of ~500 km day[sup -1]. With the exception of Belém, in northern Brazil, and Lagoa do Peixe, in southern Brazil, the coastal areas used by the tracked birds were also those with concentrations of ringing recoveries, confirming their importance as non-breeding areas for birds from the Azores. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cort in feathers grown while breeding reflect reproductive effort by giant petrels. [•] fCort was 1.5 times higher successful versus failed female breeders. [•] There were no differences in fCort between successful and failed male breeders. [•] We attribute these sex-differences to known differences in foraging ecology. [•] High fCort at breeding and slow moult predicted future breeding effort in females. [ABSTRACT FROM AUTHOR]