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Global mercury pollution has markedly and consistently grown over the past 70 years (although with regional variations in trends) and is a source of major concern. Mercury contamination is particularly prevalent in biota of the mesopelagic layers of the open ocean, but these realms are little studied, and we lack a large scale picture of contamination in living organisms of this region. The Bulwer's petrel Bulweria bulwerii, a species of migratory seabird, is a highly specialised predator of mesopelagic fish and squid, and therefore can be used as a bioindicator for the mesopelagic domain. Mercury accumulated by the birds through diet is excreted into feathers during the moulting process in adults and feather growth in chicks, reflecting contamination in the non-breeding and breeding periods, respectively, and hence the influence of different, largely non-overlapping breeding and non-breeding ranges. We studied mercury in feathers and the trophic position in two colonies from the Atlantic Ocean (Portugal and Cape Verde) and two colonies from the Pacific Ocean (Japan and Hawaii). We found significantly lower levels of mercury in adult and chick samples from the Pacific Ocean compared with samples from the Atlantic Ocean. However, we did not detect differences in trophic position of chicks among colonies and oceans, suggesting that differences in mercury measured in feathers reflect levels of environmental contamination, rather than differences in the structure of the trophic chain in different oceans. We conclude that despite a reduction in mercury levels in the Atlantic in recent decades, mesopelagic organisms in this ocean remain more heavily contaminated than in the Pacific at tropical and subtropical latitudes. We suggest that Bulwer's petrel is a highly suitable species to monitor the global contamination of mercury in the mesopelagic domain. info:eu-repo/semantics/publishedVersion

Marine plastic pollution is rapidly growing and is a source of major concern. Seabirds often ingest plastic debris and are increasingly used as biological monitors of plastic pollution. However, virtually no studies have assessed plastics in seabirds in the deep subtropical North Atlantic. We investigated whether remains of white-faced storm-petrels (WFSP) present in gull pellets could be used for biomonitoring. We analysed 263 pellets and 79.0% of these contained plastic debris originating in the digestive tract of WFSP. Pellets with no bird prey did not contain plastics. Most debris were fragments (83.6%) with fewer plastic pellets (8.2%). Light-coloured plastics predominated (71.0%) and the most frequent polymer was HDPE (73.0%). Stable isotopes in toe-nails of WFSP containing many versus no plastics did not differ, indicating no individual specialisation leading to differential plastic ingestion. We suggest WFSP in pellets are highly suitable to monitor the little known pelagic subtropical Northeast Atlantic. Fundação para a Ciência e a Tecnologia (FCT)

Individuals within populations can use different resources, leading to ecological segregation and niche variation. This segregation could have direct impacts on the migratory strategy or breeding success, thus affecting the overall population and community dynamics and, ultimately, survival. In this study, we assessed the inter-annual and within individual foraging ecology of an endemic and highly threatened seabird species, the Desertas petrel Pterodroma deserta, during the breeding and non-breeding phases. We combined 54 annual tracks (26 individuals; 2009–2013) obtained with light-level loggers (Global Location Sensing or GLS loggers) with stable isotope analyses (δ15N and δ13C) of blood (plasma and cells) and feathers. Wide-ranging tracking data show that this species is a generalist predator, able to adapt to very different habitats. All birds remained faithful to their selected non-breeding areas over the years leading to very high spatial, temporal and trophic consistency among years (i.e. usually with intra-correlation coefficient values, which is an index of repeatability of > 40%). During both the breeding and non-breeding seasons, individual birds showed narrow and segregated isotopic niches, indicating a high level of specialization and limited choice of prey and habitats. The conservation of a seabird with such a dispersive (species-level) yet consistent (individual-level) non-breeding distribution pattern represents a challenge in marine policy terms. On the one hand, such a consistent temporal and spatial pattern will help with defining core areas for conservation, which could be protected through specific management measures or by the establishment of marine protected areas. Yet, their relatively large size (on average 4000 km2) and extent over both national and international waters, where different legislative frameworks apply, will require the coordinated action by many nations, international organizations and multilateral environmental agreements.

Invasive ants have the potential to cause severe impacts on the structure and composition of native invertebrate communities and interfere with the natural processes of pollination and seed dispersal. Less frequently reported, direct and indirect impacts on vertebrates, namely birds, are also known to occur. The Argentine ant Linepithema humile is one of the worst invasive species worldwide, and is responsible for economic and ecological impacts in Madeira since its introduction. Previous reports indicated that Argentine ants may be a frequent predator of nestlings on the Desertas Islands which harbour internationally important seabird colonies. Here, we provide a survey of the records of bird predation by Argentine ants in the Desertas. Furthermore, we also assessed if these invasive ants affected the most abundant crevice-nesting seabird on Deserta Grande, the Bulwer’s petrel Bulweria bulwerii, by nest monitoring in the years of 2014–2016. We found that breeding success varied annually between 0.56 and 0.63 chicks produced per nesting attempt. Ant predation of chicks was observed in only two out of 294 study nests. Furthermore, no relationship was found between local abundance of Argentine ants and breeding success of Bulwer’s petrels. We conclude that Argentine ants do not seem to pose a major threat to nesting petrels on the Desertas, although we acknowledge the possibility that environmental changes and episodic population explosions of this invasive species may lead to a greater impact on seabirds’ reproductive success. European Regional Development Fund through Program LIFE Recover Natura; Fundação para a Ciência e a Tecnologia (FCT) info:eu-repo/semantics/publishedVersion

Seabirds due to their status as sentinels of the marine environment can indicate qualitative changes at various levels of the food web. Furthermore, changes in marine productivity have been correlated with fluctuations in large-scale atmospheric conditions driven by global indices, such as the North Atlantic Oscillation (NAO) index. During the winter of 2009/2010, the second lowest NAO index in history was recorded leading to detrimental conditions that influenced productivity levels in the northeast Atlantic. The response of the Cory’s Shearwater Calonectris borealis, during the period of ameliorating climatic conditions from this drastic event, was monitored in two islands with contrasting productivity patterns: Berlenga, located on the rich upwelling area of the Portuguese shelf; and Cima Islet (Porto Santo Island), located in a poor oceanic environment in the Madeira Archipelago. We collected a multi-year GPS-tracking data set (2011–2015) from adult breeders during the chick-rearing season to examine their at-sea foraging distribution. During a year of low productivity, kernel estimations demonstrated that Cima Islet birds expanded their home ranges and core foraging areas all over the northeast Atlantic, whereas Berlenga birds maintained their distribution close to the breeding colony. Once oceanographic conditions ameliorated from 2012 to 2015, birds decreased significantly their foraging effort, and oceanic breeders concentrated their activity closer to the breeding colony. Analysis of habitat use by means of Maximum Entropy Modelling confirmed distance-to-colony as the most important predictor in the distribution of Cory’s Shearwater. Environmental variables describing sea surface temperature, bathymetry, and chlorophyll a were more influential in Porto Santo, indicating higher sensitivity of the oceanic population to marine productivity proxies. Our study confirms that the Cory’s Shearwater possesses enormous flexibility in its foraging tactics and that neither oceanic nor neritic populations disperse randomly from their breeding colonies to the open ocean even under conditions of environmental stochasticity. Instead, populations breeding in contrasting environments vary in their responses according to their strategies and to the changing levels of marine productivity in the surroundings of their colonies.

The yellow-legged Gull Larus michahellis atlantis (YLG) is a generalist and opportunistic species that explores different habitats and resources and easily adapts to humanised environments, sometimes posing problems related to aircraft security, public health or predation on other species, for example. we examined the distribution and foraging behaviour of YLGs on the oceanic island of Madeira. GPS-GSM devices were deployed on ten breeding individuals and samples of blood (adults) and feathers (chicks) were collected to examine their stable isotope signatures in relation to those of their prey. Tracked YLGs did not migrate. Birds remained mostly inland during the day (up to 60% of fixes) and barely 5% of the fixes were at sea. Eighty-eight out of 192 gull trips to the sea were in interaction with local fishing vessels, 91% of which involving purse seiners that were active at night. The diet of the adult YLGs consisted of refuse, fish and small petrels, whereas the chick diet included mainly fish. YLGs on this oceanic island are strongly dependent on anthropogenic resources, scarcely relying on natural marine prey. The desired control of this gull population could perhaps be achieved by the reduction of accessibility to organic waste.-Romero, J., Catry, P., Menezes, D., Coelho, N., Silva, J.P. & Granadeiro, J.P. (2019). A gull that scarcely ventures on the ocean: yellow-legged Gulls Larus michahellis atlantis on the oceanic island of Madeira. Ardeola, 66: 101–112.

The Portuguese island of Selvagem Grande (Great Salvage) in Macaronesia is an important seabird breeding station in the eastern Atlantic. Significant populations of Cory's shearwater Calonectris diomedea (Scopoli, 1769), Bulwer's petrel Bulweria bulweria (Jardine & Selby, 1828) and little shearwater Puffinus assimilis baroli (Bonaparte, 1857) are present, and white-faced storm-petrel Pelagodroma marina (Latham, 1790) and Madeiran storm-petrel Oceanodroma castro (Harcourt, 1851) populations are of global significance. Selvagem Grande also provides diverse habitats for an extensive flora, including 11 endemic species. The 270-ha island was also inhabited by two alien invasive mammals: the European rabbit Oryctolagus cuniculus (Linnaeus, 1758) and the house mouse Mus musculus (Linnaeus, 1758). Both are known to have had adverse impacts on breeding seabirds and island vegetation. In 2002, the Natural Park of Madeira conducted a program using brodifacoum bait formulations aimed at rabbit and mouse eradication. Approximately 17 000 individual baiting points were established on a 12.5 × 12.5 m grid. Baits were also applied by hand "seeding" on steep slopes and cliffs where bait stations could not be placed. Rabbits were removed after a month. However, mice persisted for considerably longer and strategic bait applications against them continued for a further six months. Subsequent assessments by trapping, bait takes and systematic observation of signs over three years, has confirmed the removal of both alien invasive species. This paper presents information on these operations, on measures adopted to mitigate adverse impacts of the eradication program on important vertebrate non-target species, including Berthelot's pipit Anthus berthelotii Bolle, 1862 and a species of gecko Tarentola bischoffi Joger, 1984 and on the initial response of the island's ecosystem to the eradication of rabbits and mice.

This study was conducted over a two year period in the north west of Madeira Island (Macaronesian Atlantic Islands, Portugal). It investigates the relationship between fruiting patterns in the indigenous forest and the use by the Madeira laurel pigeon of forest habitats and cultivated areas. Habitat use observations were carried out using line-transects in forest sites where the availability of fruit (the most important element of the diet) was assessed. The use of agricultural fields was measured indirectly by the assessment of the damage caused to crops. The findings provided strong evidence that bird movements and shifts in abundance are related to fruit usage and availability. The use of fruits is mostly opportunistic but when many species are available, selection was observed. From an ecological perspective, our findings indirectly confirm a high concordance between pigeon diet, studied by microhistological techniques, and habitat use. The use of crops also seems to be mostly opportunistic and is governed by the birds’ movements within the adjacent forest. It is hypothesised that fruit phenology will influence the use of agricultural areas only to the extent that it governs such movements; there is no strong evidence that crops are attacked only when the availability of natural foods is low. Our results suggest that the current management strategy for the forest is adequate for the conservation of this pigeon but that the conservation value of forest edges should be redefined. It is also proposed that crop damage may be reduced by identifying the proximate factors, which lead to the use of specific fields.

Copyright © Crespo L et al.. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Madeira island presents a unique spider diversity with a high number of endemic species, many of which are still poorly known. A recent biodiversity survey on the terrestrial arthropods of the native forest, Laurisilva, provided a large set of standardized samples from various patches throughout the island. Out of the fifty two species recorded, approximately 33.3% are Madeiran endemics, many of which had not been collected since their original description. Two new species to science are reported – Ceratinopsis n. sp. and Theridion n. sp. – and the first records of Poeciloneta variegata (Blackwall, 1841) and Tetragnatha intermedia Kulczynski, 1891 are reported for the first time for Madeira island. Considerations on species richness and abundance from different Laurisilva locations are presented, together with distribution maps for endemic species. These results contribute to a better understanding of spider diversity patterns and endemic species distribution in the native forest of Madeira island.

SummaryA survey was undertaken in 1995 to assess the conservation status of the Madeira Laurel Pigeon Columba trocaz, a threatened species endemic to the Island of Madeira. The first large scale survey was carried out 1986, following the cessation of legal hunting of the species, to provide a baseline for future monitoring of population changes. The current study therefore aims to (1) compare population size with those of 1986 and (2) employ distance sampling methods (not used in 1986) to obtain estimates of population density and size. Eighteen transects (13 repeated from the 1986 survey and five new) were conducted in the four main areas of laurel forest. Pigeon numbers had increased on nearly all transects but some of the highest increases, proportionately and often numerically, were in areas with lower numbers in 1986. We estimate the current population to be 10,400 individuals, a considerable increase since 1986, probably due to a ban on hunting. As laurel forest habitat is now very well protected the Madeira Laurel Pigeon is relatively safe from extinction.

The conservation of threatened seabirds that are highly pelagic, such as the gadfly petrels Pterodroma spp., depends on understanding the main oceanographic determinants of their movements in order to apply the necessary management regulations and to identify and protect their key marine habitats. The present work presents for the first time information on the distribution and habitat preferences of 17 Bugio petrels Pterodroma deserta from the island of Bugio, Madeira archipelago, North Atlantic Ocean. All of the birds remained in North Atlantic waters during the pre-laying exodus, incubation and chick-rearing periods, showing a clear preference for deep, productive (high chlorophyll a levels) waters north of the Azores archipelago. There was high individual variability in migration strategies. Five wintering areas were identified: two off the Brazilian coast, one around the Cape Verde archipelago, one off the southeast coast of the United States, and one in pelagic waters in the central South Atlantic. These tended to be areas of high productivity but not of a particular sea surface temperature regime. Based on saltwater immersion data, birds were more active during the breeding season and spent more time resting on the water in wintering areas. There was also a positive correlation between the time spent on the water and the progression of full to new moon, suggesting that the birds may use moonlight to search for prey. Given its highly dispersed distribution at sea throughout the year, effective conservation of this threatened species may require management at large spatial scales.

Feral cats Felis catus Linnaeus, 1758 have contributed to the extinction of numerous native species on islands, which are clearly sources of global biodiversity. We studied the diet of this introduced predator in the Madeira and Cape Verde archipelagos, which harbour important colonies of endangered seabirds in the high mountain habitats, and compared the results with those obtained in the same habitat in the Canary Islands, Macaronesian archipelago. On Madeira, 461 prey were identified from 143 scat groups. Mammals, overall mice, constituted the basic diet appearing in 95% of cat scats. On Fogo (Cape Verde), 657 prey items were obtained from 145 scats, and mammals were also the most important prey, reaching a frequency of occurrence of 88%. Although introduced mammals were the main prey category on all Macaronesian islands, we observed variation in feral cat diet among these islands. Birds were more frequently consumed on Madeira, lizards on Tenerife (Canaries) and invertebrates on Fogo. No specific differences were observed in relation to La Palma. We suggest that the diet composition on these islands varies according to the respective availability of the different prey types.

It is widely accepted that the gadfly petrels of the Macaronesian islands comprise three closely related and morphologically similar taxa, Petrodroma madeira from Madeira island, P. deserta (also treated as P. feae deserta) from Bugio and P. feae (also treated as P. feae feae) from Cape Verde Islands. However, the taxonomic rank of each taxon is not well defined, and has been subject to a long debate. Partial sequences of cytochrome b (893 bp) from 39 individuals (five from Madeira, 18 from nearby Bugio, and 16 from Fogo) and morphometric data from five characters from 102 individuals (74 from Bugio and 28 from Fogo in Cape Verde), were used to compare and estimate phylogenetic relationships and the taxonomic status of these petrels. In the phylogenetic analysis and sequence divergence estimation, we also include 23 sequences of 19 Pterodroma species available from GenBank. Our results show that Macaronesian gadfly petrels form a monophyletic clade. Birds from Bugio and Cape Verde are the most closely related taxa followed by those from Madeira. The group formed by the three taxa studied is closely related to Bermuda Petrel P. cahow and Black-capped Petrel P. hasitata. A hypothesis for the colonization of the islands is presented. The level of sequence divergence is sufficient to consider the populations of Bugio and Cape Verde as separate species. Reproductive isolation is supported by exclusive haplotypes and fixed changes. Despite the presence of some significant differences in bill and tarsus measurements, the two species seem to be morphologically similar because the great overlap of variation intervals in the measurements hinders identification. It therefore appears suitable for consideration as a cryptic species. An important conservation implication is that the world population of both species is very small; if treated as a full species, deserta on Bugio may qualify for uplisting to ‘Vulnerable’ on the IUCN Red List., This project was supported by the EC, through the Life project SOS Bugio Petrel (LIFE06NAT/ PT/000184)

Several species of seabirds show cyclic patterns of attendance at their nesting colonies. We examined the patterns of variation in the numbers of Cory's shearwater at three colonies (two oceanic and one located on the continental shelf), including the world's largest, at Selvagem Grande, Madeira, Portugal and considered several hypotheses concerning their causal mechanisms. At Selvagem Grande, cycles were exceptionally marked and regular, with a periodicity ranging from 7.8 to 11 days, and involved both breeders and nonbreeders. In contrast, variation in numbers was aperiodic at a nearby and much smaller colony (Selvagem Pequena), and also at the colony located off the Portuguese coast (Berlenga Island). We found no relationships between number of birds ashore and environmental variables such as wind direction and speed or lunar cycle. Cycles did not seem to be driven by oscillations in food availability or accessibility, given that they did not correlate with daily chick growth rates (which were acyclic) or diet. Despite their regularity, cycles were slightly out of phase in different sectors of Selvagem Grande, which suggests that social interactions at the colony could act as an entrainment agent for an endogenous rhythm, and so cycles are probably more likely to occur in large and dense colonies. Observations are consistent with the hypothesis that cycles facilitate social interactions by maximizing the probability of encounters at the colony. However, the exact mechanisms through which these remarkable cycles are controlled are still completely unknown, and clearly further research is needed.