Little change in plastic loads in South Atlantic seabirds since the 1980s.

Despite growing concern about the large amounts of waste plastic in marine ecosystems, evidence of an increase in the amount of floating plastic at sea has been mixed. Both at-sea surveys and ingested plastic loads in seabirds show inconsistent evidence of significant increases in the amount of plastic since the 1980s. We use 3727 brown skua Catharacta antarctica regurgitations, each containing the remains of a single seabird, to monitor changes in plastic loads in four seabird taxa breeding at Inaccessible Island, Tristan da Cunha in nine years from 1987 to 2018. Frequency of occurrence in plastic ingestion and types were compared across four near-decadal time periods (1987-1989; 1999-2004; 2009-2014 and 2018) while loads were compared among years. The number and proportions of industrial pellets among ingested plastic decreased consistently over the study period in all four taxa, suggesting that industry initiatives to reduce pellet leakage have reduced the numbers of pellets at sea. Despite global plastic production increasing more than four-fold over the study period, there was no consistent increase in the total amount of ingested plastic in any species. Plastic loads in great shearwaters Ardenna gravis, which spend the austral winter in the North Atlantic Ocean, increased in 2018, but the proportion of shearwaters containing plastic decreased. We conclude that the density of plastic floating at sea has not increased in line with global production over the last 30 years.

Regurgitated skua pellets containing the remains of South Atlantic seabirds can be used as biomonitors of small buoyant plastics at sea.

Using seabirds as bioindicators of marine plastic pollution requires an understanding of how the plastic retained in each species compares with that found in their environment. We show that brown skua Catharacta antarctica regurgitated pellets can be used to characterise plastics in four seabird taxa breeding in the central South Atlantic, even though skua pellets might underrepresent the smallest plastic items in their prey. Fregetta storm petrels ingested more thread-like plastics and white-faced storm petrels Pelagodroma marina more industrial pellets than broad-billed prions Pachyptila vittata and great shearwaters Ardenna gravis. Ingested plastic composition (type, colour and polymer) was similar to floating plastics in the region sampled with a 200 µm net, but storm petrels were better indicators of the size of plastics than prions and shearwaters. Given this information, plastics in skua pellets containing the remains of seabirds can be used to track long-term changes in floating marine plastics.

Female and male Leach's Storm Petrels (Hydrobates leucorhous) pursue different foraging strategies during the incubation period.

Reproduction in procellariiform birds is characterized by a single egg clutch, slow development, a long breeding season and obligate biparental care. Female Leach's Storm Petrels Hydrobates leucorhous, nearly monomorphic members of this order, produce eggs that are between 20 and 25% of adult body weight. We tested whether female foraging behaviour differs from male foraging behaviour during the ~ 44-day incubation period across seven breeding colonies in the Northwest Atlantic. Over six breeding seasons, we used a combination of Global Positioning System and Global Location Sensor devices to measure characteristics of individual foraging trips during the incubation period. Females travelled significantly greater distances and went farther from the breeding colony than did males on individual foraging trips. For both sexes, the longer the foraging trip, the greater the distance. Independent of trip duration, females travelled farther, and spent a greater proportion of their foraging trips prospecting widely as defined by behavioural categories derived from a Hidden Markov Model. For both sexes, trip duration decreased with date. Sex differences in these foraging metrics were apparently not a consequence of morphological differences or spatial segregation. Our data are consistent with the idea that female foraging strategies differed from male foraging strategies during incubation in ways that would be expected if females were still compensating for egg formation.

Infestation of small seabirds by Ornithodoros maritimus ticks: Effects on chick body condition, reproduction and associated infectious agents.

Ticks can negatively affect their host by direct effects as blood feeding causing anaemia or discomfort, or by pathogen transmission. Consequently, ticks can have an important role in the population dynamics of their hosts. However, specific studies on the demographic effects of tick infestation on seabirds are still scarce. Seabird ticks have also the potential to be responsible for the circulation of little known tick-borne agents, which could have implications for non-seabird species. Here, we report the results of investigations on potential associations between soft tick Ornithodoros maritimus load and reproductive parameters of storm petrels Hydrobates pelagicus breeding in a large colony in a cave of Espartar Island, in the Balearic archipelago. We also investigated by molecular analyses the potential viral and bacterial pathogens associated with O. maritimus ticks present at the colony. Lower nestling survival was recorded in the most infested area, deep in the cave, compared to the area near the entrance. The parasite load was negatively associated with the body condition of the nestlings. One pool of ticks tested positive for West Nile virus and 4 pools tested positive for a Borrelia species which was determined by targeted nested PCR to have a 99% sequence identity with B. turicatae, a relapsing fever Borrelia. Overall, these results show that further investigations are needed to better understand the ecology and epidemiology of the interactions between ticks, pathogens and Procellariiform species.

Differences in tail feather growth rate in storm-petrels breeding in the Northern and Southern hemisphere: a ptilochronological approach.

Moulting and breeding are costly stages in the avian annual cycle and may impose trade-offs in energy allocation between both stages or in their timing. Here, we compared feather growth rates (FGR) of rectrices in adults between two pairs of small pelagic Procellariiformes species differing in moult-breeding strategies: the European storm-petrel Hydrobates pelagicus and Leach's storm-petrel Oceanodroma leucorhoa breeding in the Northern Hemisphere (Faroe Islands), showing moult-breeding overlap in tail feathers; and the Wilson's storm-petrel Oceanites oceanicus and black-bellied storm-petrel Fregetta tropica, breeding in the Southern Hemisphere (South Shetlands), temporally separating moult and breeding. We used ptilochronology (i.e., feather growth bar width) to reconstruct FGR reflecting relative energy availability during moult. Based on previous research, we expected positive correlations between feather length (FL) and FGR. Additionally, we expected to find differences in FGR relative to FL between the moult-breeding strategies, where a relatively higher FGR to FL indicates a higher energy availability for moult. To investigate if energy availability during moult in the studied species is similar to species from other avian orders, we used FGR and FL found in literature (n = 164) and this study. We fitted a phylogenetic generalized least squares (PGLS) model to FGR with FL, group (i.e., Procellariiformes vs. non-Procellariiformes) and the interaction FL * group as predictors. As it has been suggested that Procellariiformes may form two growth bars per 24 h, we fitted the same model but with doubled FGR for Procellariiformes (PGLSadj). The group term was significant in the PGLS model, but was not in the PGLSadj model, confirming this suggestion. Individually predicted FGR by the PGLSadj model based on FL, showed that the Southern species have a significantly higher FGR relative to FL compared to the Northern species. Additionally, we found no correlation between FL and FGR in the Northern species, and a positive correlation between FL and FGR in the Southern species, suggesting differences in the trade-off between feather growth and size between species from both hemispheres. The observed differences between the Northern and Southern species may be caused by different moult-breeding strategies. The Southern species may have had more energy available for moult as they are free from breeding duties during moult, while the Northern species may have had less free energy due to a trade-off in energy allocation between breeding and moulting. Our study shows how different moult-breeding strategies may affect relative nutritional condition or energy allocation during moult of migratory pelagic seabirds.

Annual global mean temperature explains reproductive success in a marine vertebrate from 1955 to 2010.

The salient feature of anthropogenic climate change over the last century has been the rise in global mean temperature. However, global mean temperature is not used as an explanatory variable in studies of population-level response to climate change, perhaps because the signal-to-noise ratio of this gross measure makes its effect difficult to detect in any but the longest of datasets. Using a population of Leach's storm-petrels breeding in the Bay of Fundy, we tested whether local, regional, or global temperature measures are the best index of reproductive success in the face of climate change in species that travel widely between and within seasons. With a 56-year dataset, we found that annual global mean temperature (AGMT) was the single most important predictor of hatching success, more so than regional sea surface temperatures (breeding season or winter) and local air temperatures at the nesting colony. Storm-petrel reproductive success showed a quadratic response to rising temperatures, in that hatching success increased up to some critical temperature, and then declined when AGMT exceeded that temperature. The year at which AGMT began to consistently exceed that critical temperature was 1988. Importantly, in this population of known-age individuals, the impact of changing climate was greatest on inexperienced breeders: reproductive success of inexperienced birds increased more rapidly as temperatures rose and declined more rapidly after the tipping point than did reproductive success of experienced individuals. The generality of our finding that AGMT is the best predictor of reproductive success in this system may hinge on two things. First, an integrative global measure may be best for species in which individuals move across an enormous spatial range, especially within seasons. Second, the length of our dataset and our capacity to account for individual- and age-based variation in reproductive success increase our ability to detect a noisy signal.

Phylogenetic affinities of the Fregetta storm-petrels are not black and white.

The Fregetta storm-petrels generally are regarded to comprise two species: black-bellied storm-petrels F. tropica (monotypic) breed at Antarctic and sub-Antarctic islands (46-63°S), and white-bellied storm-petrels F. grallaria breed at south temperate islands (28-37°S), with four recognized subspecies. Confusion surrounds the status of birds at Gough Island (40°S), central South Atlantic, which have been attributed usually to a white-bellied form of black-bellied storm-petrel F. t. melanoleuca. We use cytochrome b and nuclear ß-fibrinogen gene sequences to show that F. t. melanoleuca are present during the breeding season at Gough and islands in the nearby Tristan da Cunha archipelago (37°S), exhibiting limited divergence from F. t. tropica. We also show that there is greater diversity among F. grallaria populations, with eastern South Pacific F. g. segethi and F. g. titan differing by c. 0.011, and both differing from western South Pacific nominate F. g. grallaria by c. 0.059. The Tristan archipelago supports a population of F. grallaria closely allied to the nominate form, as well as a distinct form identified as F. g. leucogaster. Further research is needed to assess how F. grallaria and F. tropica segregate in sympatry at Tristan and Gough, and why this is the only location where both species have white-bellies.