Beached Birds Research Articles

Pattern and intensity of moult in White-capped/Shy Albatrosses Thalassarche steadi/cauta

Albatrosses typically only replace a subset of flight feathers each annual moult cycle. We scored the moult of 662 White-capped/Shy Albatrosses Thalassarche steadi/cauta, using birds that had been killed by longline fisheries off South Africa. Most adults and immatures alternated replacing the outer primaries (phase 1) and inner primaries (phase 2), but there was considerable variation among adults, with 0–10 primaries replaced each moult cycle. Birds in phase 1 moult replaced fewer primaries than birds in phase 2, but the proportion by mass was similar. Adults replaced more primaries than immatures as there was a disproportionate number of adults in phase 2 moult (82%), which might indicate that most adults off South Africa are in their first year after a successful breeding attempt, but a similar bias occurred among beached birds from New Zealand and Australia. The outer primaries were usually replaced outwards from P8, but the replacement sequence was more variable among the inner primaries. Secondary moult overlapped with primary moult, but not all secondaries were moulted each year. Adults had more active moult centres and replaced more secondaries at once than immatures. Tail moult started after primary moult, with 1–11 feathers growing from 1–6 active centres. Some birds replaced their rectrices in pairs, with often 2 or 3 pairs moulting at once, but others replaced alternate feathers or almost all rectrices at once. A few birds exhibited intense wing moult, but the norm was to replace only 1 or 2 primaries and 1–6 secondaries at once. Age- and sex-related differences in moult intensity presumably result from different time constraints. Adult White-capped/Shy Albatrosses take a year off between successful breeding attempts, allowing time for a more protracted moult. However, we cannot explain the intense moult in some immatures. Our findings support recent studies showing that albatross flight feather moult patterns are more varied than previously reported.

Temporal trends and interannual variation in plastic ingestion by Flesh-footed Shearwaters (Ardenna carneipes) using different sampling strategies

The world's oceans are under increasing pressure from anthropogenic activities, including significant and rapidly increasing inputs of plastic pollution. Seabirds have long been considered sentinels of ocean health, providing data on physical and chemical pollutants in their marine habitats. However, long-term data that can elucidate important patterns and changes in seabird exposure to marine pollutants are relatively limited but are urgently needed to identify and support effective policy measures to reduce plastic waste. Using up to 12 years of data, we examined the benefits and challenges of different approaches to monitoring plastic in seabirds, and the relationship between plastic and body size parameters. We found the mass and number of ingested plastics per bird varied by sample type, with lavage and road-kill birds containing less plastic (9.17–9.33 pieces/bird) than beach-washed or otherwise dead birds (27.62–32.22 pieces/bird). Beached birds therefore provide data for only a particular subset of the population, mostly individuals in poorer body condition, including those severely impacted by plastics. In addition, the mass and number of plastics in beached birds were more variable, therefore the sample sizes required to detect a change in plastic over time were significantly larger than for lavaged birds. The use of lavaged birds is rare in studies of plastic ingestion due to ethical and methodological implications, and we recommend future work on ingested plastics should focus on sampling this group to ensure data are more representative of a population's overall exposure to plastics.

Ingested plastics in northern fulmars (Fulmarus glacialis): A pathway for polybrominated diphenyl ether (PBDE) exposure?

Although it has been suggested that plastic may act as a vector for pollutants into the tissue of seabirds, the bioaccumulation of harmful contaminants, such as polybrominated diphenyl ethers (PBDEs), released from ingested plastics is poorly understood. Plastic ingestion by the procellariiform species northern fulmar (Fulmarus glacialis) is well documented. In this study, we measured PBDEs levels in liver tissue of northern fulmars without and with (0.13-0.43g per individual) stomach plastics. PBDE concentrations in the plastic sampled from the same birds were also quantified. Birds were either found dead on beaches in southern Norway or incidentally caught in longline fisheries in northern Norway. PBDEs were detected in all birds but high concentrations were only found in liver samples from beached birds, peaking at 2900ng/g lipid weight. We found that body condition was a significant factor explaining the elevated concentration levels in livers of beached birds. BDE209 was found in ingested plastic particles and liver tissue of birds with ingested plastics but was absent in the livers of birds without ingested plastics. This strongly suggests a plastic-derived transfer and accumulation of BDE209 to the tissue of fulmars, levels of which might prove useful as a general indicator of plastic ingestion in seabirds.

Modelling distribution of common scoter (Melanitta nigra) by its predominant prey, the American razor clam (Ensis leei) and hydrodynamic parameters

The non-breeding distribution of common scoter (Melanitta nigra), which occur in high densities offshore from the eastern Wadden Sea, has been well documented in recent decades, but factors influencing these patterns remain poorly known. We investigated the prey choice of 88 common scoter using stomach contents of beached birds collected over a period of 12 years. We then used benthos data and hydrodynamic parameters to model the June–September distribution patterns during the flightless period of common scoter based on transect count data off the north-eastern German Wadden Sea.Benthic fauna biomass in areas used by common scoter was higher than in areas where the species was absent. American razor clam (Ensis leei) invaded the Wadden Sea during the end of the 1970s and was the most common prey, both in benthos samples from below feeding common scoter and in stomach samples. The relatively high flesh to shell ratio of the American razor clam makes it the most attractive available prey item for common scoter.The abundance of American razor clams explained the distribution of scoter to a high degree, although the best model fit included negative effects of water depth and positive effects of bed shear stress intensity on scoter abundance. Our data show that the neobiotic American razor clams have become an important part of the diet of these sea ducks, whereas the cut trough shell (Spisula subtruncata) was of substantially lesser importance than expected from historical data. Our study shows the ability of a top avian predator to respond to novel developments in bivalve prey availability over periods of a few decades.

Unusual mortality of Tufted puffins (Fratercula cirrhata) in the eastern Bering Sea.

Mass mortality events are increasing in frequency and magnitude, potentially linked with ongoing climate change. In October 2016 through January 2017, St. Paul Island, Bering Sea, Alaska, experienced a mortality event of alcids (family: Alcidae), with over 350 carcasses recovered. Almost three-quarters of the carcasses were unscavenged, a rate much higher than in baseline surveys (17%), suggesting ongoing deposition and elevated mortality around St Paul over a 2–3 month period. Based on the observation that carcasses were not observed on the neighboring island of St. George, we bounded the at-sea distribution of moribund birds, and estimated all species mortality at 3,150 to 8,800 birds. The event was particularly anomalous given the late fall/winter timing when low numbers of beached birds are typical. In addition, the predominance of Tufted puffins (Fratercula cirrhata, 79% of carcass finds) and Crested auklets (Aethia cristatella, 11% of carcass finds) was unusual, as these species are nearly absent from long-term baseline surveys. Collected specimens were severely emaciated, suggesting starvation as the ultimate cause of mortality. The majority (95%, N = 245) of Tufted puffins were adults regrowing flight feathers, indicating a potential contribution of molt stress. Immediately prior to this event, shifts in zooplankton community composition and in forage fish distribution and energy density were documented in the eastern Bering Sea following a period of elevated sea surface temperatures, evidence cumulatively suggestive of a bottom-up shift in seabird prey availability. We posit that shifts in prey composition and/or distribution, combined with the onset of molt, resulted in this mortality event.

Seabird plastic ingestion differs among collection methods: Examples from the short-tailed shearwater

Despite the increase of literature on seabird plastic ingestion in recent years, few studies have assessed how plastic loads vary according to different sampling methods. Most studies use necropsies of seabirds with a natural cause of death, e.g. beached or predated, to determine plastic loads and monitor marine debris. Sampling naturally dead seabirds may be biased as they have perished because of their intrinsic factors, e.g. poor body condition, high parasite loads, sickness or predation, affecting estimates of plastic loads. However, seabirds killed accidentally may be more representative of the population. Here, we used the short-tailed shearwater Ardenna tenuirostris to test different sampling methods: naturally beached fledglings and accidentally road-killed fledglings after being attracted and grounded by artificial lights. We compared plastic load, body condition, and feeding strategies (through using feathers’ δ13C and δ15N isotope niche) between beached and road-killed fledglings. Beached birds showed higher plastic loads, poorer body condition and reduced isotopic variability, suggesting that this group is not a representative subsample of the whole cohort of the fledgling population. Our results might have implications for long-term monitoring programs of seabird plastic ingestion. Monitoring plastic debris through beached birds could overestimate plastic ingestion by the entire population. We encourage the establishment of refined monitoring programs using fledglings grounded by light pollution if available. These samples focus on known cohorts from the same population. The fledgling plastic loads are transferred from parents during parental feeding, accumulating during the chick-rearing period. Thus, these fledglings provide a higher and valuable temporal resolution, which is more useful and informative than unknown life history of beached birds.

Distinguishing offshore bird hunting from beach scavenging in archaeological contexts: The value of modern beach surveys

Determining whether seabirds recovered from coastal shell middens were obtained via active hunting or scavenging of beached carcasses is a challenge for archaeologists. Traditional methods have included analyzing skeletal part frequencies, abundance, age profiles, and contextual evidence. The assumption has been made, based on limited biological data, that an assemblage of carcasses scavenged from the beach will have more wing elements, and fewer legs and heads. Few studies, however, have embraced modern beaching data to verify this assumption and assess the potential faunal resources available for scavenging. We analyze the skeletal part representation of modern beached birds observed by the Coastal Observation and Seabird Survey Team (COASST), comparing the COASST dataset to two idealized hypotheses used by archaeologists: the human scavenging hypothesis (wings only are recovered, while heads and legs are absent) and the human hunting hypothesis (all body parts are found in equal proportions). Finally, we apply these results to analysis of the bird remains from the Minard site (45-GH-15), a late Holocene coastal site in Grays Harbor, Washington. We find that contemporary beached bird data are closer to replicating the human hunting hypothesis as compared to the human scavenging hypothesis, as >75% of the 19,599 carcasses in the COASST dataset had a combination of head, wings and legs. This result, and the similarity in taxonomic distribution between our contemporary beached bird data and Minard assemblage, suggests that indigenous peoples may have used scavenging as a viable means of resource acquisition in the past. Use of contemporaneous beached bird data may provide zooarchaeology with a statistically defensible baseline of information on the phenology, abundance and condition of bird carcasses.

BEACHED BIRD SURVEYS ON SABLE ISLAND, NOVA SCOTIA, 1993 TO 2009, SHOW A DECLINE IN THE INCIDENCE OF OILING

Sable Island, located about 160 km southeast of the landmass of NovaScotia, Canada, is far offshore and provides a platform for beach surveysto monitor oil pollution in Scotian Shelf waters. Sporadic beach surveysconducted there during the 1970s and 1980s indicated that oiled birds andbeached tar were common occurrences. During a survey program fromJanuary 1993 to December 2009, more than 10,800 bird corpses werefound in 171 surveys covering a total of >13,500 km of shoreline. Sixtyfourspecies were recorded, of which 52 were seabirds and waterfowl.The numbers of beached birds and species composition exhibited largefluctuations, which reflected both the seasonal distribution of species andthe effects of weather and beach conditions. The oiling rate of corpsesfor all seabirds and waterfowl combined was 28.6%, and ranged from ahigh of 69.9% in 1996 to a low of 1.4% in 2009. Alcids had the highestrates of oiling (averaging 54.3%), while lower rates were observed forshearwaters (1.9%) and Larus gulls (2.4%). The results of the 1993-2009surveys, as well as those of earlier studies in the 1970s and 1980s, indicatea declining trend in the oiling rate of beached birds on Sable Island.Keywords: oil pollution, marine pollution, seabird oiling rate, beachedbird survey, Sable Island

The role of the invasive bivalve Ensis directus as food source for fish and birds in the Dutch coastal zone

The razor clam Ensis directus was introduced to Europe presumably as larvae in ballast water around 1978. Starting in the German Bight it spread northward and southward along the continental coastline. Currently it is the most common shellfish species in the Dutch coastal zone, where it mainly occurs in the Voordelta and off the Wadden Sea islands. The mean density of E. directus in the Dutch coastal zone increased from around 2–5 individuals m −2 in the late ‘90’s to around 12–19 individuals m −2 from 2002 onwards. Diet studies show that E. directus makes up a significant proportion in the current diet of plaice, sole, dab, flounder and dragonet and in the diet of eider and common scoter. In recent years E. directus contributed 20–100% of the total wet weight in fish stomachs. The proportion E. directus in the diet increases with fish length. Based on stomach contents of oiled and beached birds and of faeces samples the recent frequency of occurrence is 85–90% in eider and 26% in common scoter. Also waders, gulls and corvids prey on E. directus but the contribution to the diet is still unquantified. Because of its great burying depth the species is not easily accessible. Fish either profit from massive die-offs that regularly occur, or they extract (probably only the smaller) individuals from the sediment. Sea ducks can extract E. directus from the sediment, while shorebirds and gulls feed on dying E. directus washing up on the shore. E. directus is possibly an important food item for fish and seabirds when they occur in high densities and in the right size classes. Since the availability depends greatly on massive die-offs, shell size, burying depth and water depth, it is probably not a very reliable food source. Judging from the role E. directus currently plays for the higher trophic levels, its introduction must have caused a major change in the food relations in its distribution area.

Post-mortem examination of Great Northern Divers Gavia immer killed in the Prestige oil spill, Galicia, Spain, 2002/03

Great Northern Divers Gavia immer collected during the impact assessment of the 2002/03 Prestige oil spill were studied and compared with similar casualties collected during three other major oil spills. It was concluded that adults tend to winter further to the north in Western Europe than juveniles, and that the sexes were evenly represented in all spills. Wing and bill lengths of adults were also compared with those of museum specimens collected during the breeding season in Canada, Greenland and Iceland in an attempt to determine the possible breeding origin of birds wintering in northwest Spain. Wing lengths suggested that Iceland and Greenland were possible breeding grounds, while the incidence of embedded gunshot (18% of adults) further suggested that at least some birds originated from Greenland, where hunting is still legal. However, biometrics and gunshot incidence alone were inconclusive in determining a possible breeding origin. DNA analyses are being considered, including comparisons with gene sequences for this species already available in the GenBank. Mortality during the Prestige oil spill may have affected 18–22% of the total wintering population in Spain. Besides oil-induced mortality, drowning in fishing gear is identified as a real threat in Galicia. A systematic beached bird survey in the region would help determine the relative importance of different causes of mortality in this species.

At-sea mortality of seabirds based on beachcast and offshore surveys

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 392:295-305 (2009) - DOI: https://doi.org/10.3354/meps08152 At-sea mortality of seabirds based on beachcast and offshore surveys Kelly M. Newton1,*, Donald A. Croll1, Hannahrose M. Nevins2, Scott R. Benson3, James T. Harvey2, Bernie R. Tershy1 1Center for Ocean Health, University of California Santa Cruz, 100 Shaffer Rd. Santa Cruz, California 95060, USA 2Moss Landing Marine Laboratories, 8272 Moss Landing Rd., Moss Landing, California 95039, USA 3NOAA Fisheries, 7544 Sandholdt Rd., Moss Landing, California 95039, USA *Email: newton.kelly@gmail.com ABSTRACT: Although seabird population biology is relatively well studied, little data exists on mortality at-sea. Beached bird surveys are used to identify patterns of seabird mortality, but resulting patterns are difficult to interpret without corresponding data on at-sea density. We examined seabird mortality relative to at-sea density in Monterey Bay, California over 10 yr by integrating data from monthly beachcast seabird and offshore seabird censuses. Beachcast seabird numbers were relatively constant (mean 2.82 ± 0.31 seabirds km–1) throughout the year. At-sea seabird density (mean 148.9 ± 16.12 seabirds km–2) peaked in the summer upwelling period and was least in the winter Davidson period. A principal components analysis of seasonal climatic, prey availability, and anthropogenic variables for Monterey Bay derived 3 significant principal components (PCs) (explaining 70% of variance) characterized by storm activity and low prey availability (PC1), river discharge and krill abundance (PC2), and oiling (PC3). These principal components were used in detailed analyses of the 2 most abundant seabird species and indicate that sooty shearwater Puffinus griseus relative mortality is greatest during decreased productivity and increased storm activity. While relative mortality of common murres Uria aalge cannot be explained by the derived principal components, relative mortality increased in late winter when prey availability decreased concurrent with the annual increase in reproductive stress. Beachcast seabird data is difficult to interpret in isolation; however, when linked to at-sea densities of seabirds, it becomes a powerful tool to examine the relative impacts of oceanography and direct human perturbations on seabird demography. KEY WORDS: Seabirds at-sea · Beached bird survey · Density · Mortality · Sooty shearwater · Common murre Full text in pdf format PreviousCite this article as: Newton KM, Croll DA, Nevins HM, Benson SR, Harvey JT, Tershy BR (2009) At-sea mortality of seabirds based on beachcast and offshore surveys. Mar Ecol Prog Ser 392:295-305. https://doi.org/10.3354/meps08152 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 392. Online publication date: October 19, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Numbers of Atlantic Puffins Fratercula arctica found on beached bird surveys in Orkney and Shetland over a 30-year period

Long-term beached bird survey data from Orkney and Shetland were examined for abnormal mortality patterns of Atlantic Puffins Fratercula arctica that coincided with decreased breeding numbers at colonies in eastern Britain. Unusually high numbers of dead Atlantic Puffins were found in the late winters of 2002/03 and 2003/04, autumn and early winter 2006, and autumn 2007, although not necessarily in both island groups at the same time. The 2007 mortality was unusual in that some adult birds were replacing their primaries.

Plastic ingestion by Procellariiformes in Southern Brazil

The Procellariiformes are the birds most affected by plastic pollution. Plastic fragments and pellets were the most frequent items found in the digestive tract of eight species of Procellariiformes incidentally caught by longline fisheries as well as beached birds in Southern Brazil. Plastic objects were found in 62% of the petrels and 12% of the albatrosses. The Great shearwater, Manx shearwater, Cory’s shearwater and Antarctic fulmar were found to have greater quantities and frequencies of occurrence of plastic. There was no significant difference in the number of plastics between the birds from longline fisheries and beached birds. No correlation was found between the number of prey and number of plastics in the digestive tract of the birds analyzed, but this does not discard the hypothesis that, in some cases, the presence of plastic in the digestive tract has a negative effect on the feeding efficiency of these birds.

Estimation of the impact of prevailing weather conditions on the occurrence of oil-contaminated dead birds on the German North Sea coast

Chronic oil pollution by illegal oil dumping in the North Sea is difficult to quantify. Beached, oil-contaminated sea birds, however, may be used as an indirect indicator. Reconstructing the drift of oil slicks and sea bird corpses in the southern North Sea for the period 1992-2003 by means of a two-dimensional numerical transport model driven by re-analysed weather data, we show with an example of two common sea bird species that the variability observed within the number of corpses registered during beached bird surveys for the German coast primarily reflects the inter-annual variability of prevailing weather conditions. This should be taken into account when interpreting the data. We propose normalisation of beached bird survey data based on numerical drift simulations to improve the recognition of trends in the level of chronic oil pollution.

An evaluation of beached bird monitoring approaches

Oil-pollution monitoring at sea through beach bird surveying would undoubtedly benefit from a further standardisation of methods, enhancing the efficiency of data collection. In order to come up with useful recommendations, we evaluated various approaches of beached bird collection at the Belgian coast during seven winters (1993–1999). Data received in a passive way by one major rehabilitation centre were compared to the results of targeted beach surveys carried out at different scales by trained ornithologists: `weekly' surveys – with a mean interval of 9 days – restricted to a fixed 16.7 km beach stretch, `monthly' surveys over the entire coastline (62.1 km) and an annual `international' survey in Belgium over the same distance at the end of February. Data collected through Belgian rehabilitation centres concern injured, living birds collected in a non-systematical way. Oil rates derived from these centres appear to be strongly biased to oiled auks and inshore bird species, and are hence of little use in assessing the extent of oil pollution at sea. The major asset of rehabilitation centres in terms of data collection seems to be their continuous warning function for events of mass mortality. Weekly surveys on a representative and large enough section rendered reliable data on oil rates, estimates of total number of bird victims, representation of various taxonomic groups and species-richness and were most sensitive in detecting events quickly (wrecks, oil-slicks, severe winter mortality, etc.). Monthly surveys gave comparable results, although they overlooked some important beaching events and demonstrated slightly higher oil rates, probably due to the higher chance to miss short-lasting wrecks of auks. Since the monthly surveys in Belgium were carried out by a network of volunteers and were spread over a larger beach section, they should be considered as best performing. Single `international beached bird surveys' in February gave reliable data on total victim number (once the mean ratio between numbers in various months is known) and oil rate (provided a sufficiently large sample can be collected), but failed in tracking events. It is a particularly attractive approach because of its long tradition, resulting in invaluable long-term databases, and the uniformity in which these surveys are organised on a large scale. The minimal distance for a monthly survey amounts to 25–30 km (40–50% of Belgian coastline) up to 40 km (65%) in order to attain sound figures for oil rate and species-richness, respectively. These distances are primarily determined by the number of bird corpses that may be collected and are hence a function of beaching intensity and corpse detection rate.

Experimental Support for a New Drift Block Design to Assess Seabird Mortality from Oil Pollution

Abstract Seabird mortality from large oil spills and chronic oil pollution is often significant. Total mortality estimates are derived from counts of dead birds that wash ashore and are corrected for numbers lost at sea. Past attempts to estimate proportion of birds that die at sea and wash ashore have included several experiments using carcasses and different types of wooden drift blocks. Results varied greatly depending on environmental conditions and distance from shore where blocks or carcasses were released. Wind seemed to be the predominant factor determining movement over large distances, whereas tidal currents influenced deposition on specific beaches. Determining timing and location of arrival of dead birds on beaches are crucial for accurate mortality estimates. Drift experiments using beached birds that have already drifted at sea for an undetermined length of time are inaccurate due to natural buoyancy loss and decomposition. To determine accuracy of drift block designs used in the past, we compared drift characteristics and patterns between four drift block designs and fresh murre (Uria spp.) carcasses. Our experiments showed that drift blocks used in the past have none of the drift characteristics of dead seabirds, because they have much larger areas exposed to wind and hence drift much faster and farther than murre carcasses. Past mortality estimates using those blocks are therefore doubtful. The drift block design that most accurately mimicked murre carcass drift during our experiments was a 9 × 9 × 14.5 cm wooden block with a 450 gram steel weight that adjusts buoyancy and area exposed to the wind. We propose that in areas where murres are predominant victims of oil spills, that block design be used for all future estimates of oiled seabird mortality.

Experimental Support for a New Drift Block Design to Assess Seabird Mortality from Oil Pollution

Seabird mortality from large oil spills and chronic oil pollution is often significant. Total mortality estimates are derived from counts of dead birds that wash ashore and are corrected for numbers lost at sea. Past attempts to estimate proportion of birds that die at sea and wash ashore have included several experiments using carcasses and different types of wooden drift blocks. Results varied greatly depending on environmental conditions and distance from shore where blocks or carcasses were released. Wind seemed to be the predominant factor determining movement over large distances, whereas tidal currents influenced deposition on specific beaches. Determining timing and location of arrival of dead birds on beaches are crucial for accurate mortality estimates. Drift experiments using beached birds that have already drifted at sea for an undetermined length of time are inaccurate due to natural buoyancy loss and decomposition. To determine accuracy of drift block designs used in the past, we compared drift characteristics and patterns between four drift block designs and fresh murre (Uria spp.) carcasses. Our experiments showed that drift blocks used in the past have none of the drift characteristics of dead seabirds, because they have much larger areas exposed to wind and hence drift much faster and farther than murre carcasses. Past mortality estimates using those blocks are therefore doubtful. The drift block design that most accurately mimicked murre carcass drift during our experiments was a 9 × 9 × 14.5 cm wooden block with a 450 gram steel weight that adjusts buoyancy and area exposed to the wind. We propose that in areas where murres are predominant victims of oil spills, that block design be used for all future estimates of oiled seabird mortality.

Marine oil pollution and beached bird surveys: the development of a sensitive monitoring instrument

One of the most obvious adverse effects of (chronic) pollution of the world's oceans and seas with mineral oil is the mortality of seabirds. Systematic surveys of beachcast corpses of birds (‘beached bird surveys') have been used in many parts of the world to document the effect of oil pollution, but particularly so in Western Europe and in parts of North America. In this paper, the history, current schemes, methods and possible (future) use of beached bird surveys are described and discussed, because the value of beached bird surveys has been hotly disputed. Oil pollution is known since the late 19 th century, while the first beached bird surveys were conducted in the 1920s. Due to the amount of man-power needed for these surveys, most beached bird survey programs thrived only through the work of a large number of volunteers. However, most programs have resulted in substantial amounts of high quality data, often covering many consecutive years. One of the main shortcomings of many beached bird survey programs was the emphasis on stranded bird numbers rather than on relative measures, such as oil rates (percentage of corpses oiled of all corpses found). Sources of pollution, particularly so in chronically polluted regions such as the North Sea, the Baltic, the Mediterranean and the waters around Newfoundland, are insufficiently known, but could be studied through a sampling program connected to beached bird surveys. Suggestions for standardization of methods are presented, which could lead to a global and highly sensitive monitoring instrument of marine oil pollution.

Experimental Support for a New Drift Block Design to Assess Seabird Mortality from Oil Pollution

Abstract Seabird mortality from large oil spills and chronic oil pollution is often significant. Total mortality estimates are derived from counts of dead birds that wash ashore and are corrected for numbers lost at sea. Past attempts to estimate proportion of birds that die at sea and wash ashore have included several experiments using carcasses and different types of wooden drift blocks. Results varied greatly depending on environmental conditions and distance from shore where blocks or carcasses were released. Wind seemed to be the predominant factor determining movement over large distances, whereas tidal currents influenced deposition on specific beaches. Determining timing and location of arrival of dead birds on beaches are crucial for accurate mortality estimates. Drift experiments using beached birds that have already drifted at sea for an undetermined length of time are inaccurate due to natural buoyancy loss and decomposition. To determine accuracy of drift block designs used in the past, we co...

Beached bird surveys indicate decline in chronic oil pollution in the North Sea

Strandings of oiled seabirds have been a signal of the ongoing problem of chronic oil pollution in the North Sea since the beginning of the twentieth century. Overall numbers of beached birds are subject to enormous fluctuations, being the result, for example, of changes in the amount of oil spilled in the marine environment, currents, the frequency of onshore winds and variations in the numbers of seabirds in a given region. In contrast, oil rates, being the fraction of oiled birds of the total stranded, appeared to be relatively constant while specific for different species and regions. These species-specific oil rates are thought to reflect the risk for birds or corpses of birds to become oil fouled at sea and hence to mirror fluctuations in the amount of oil spilled in different regions. High oil rates are typical for mainly swimming, highly exposed seabirds in areas with frequent oil spills (e.g. around shipping lanes and near the major harbours); low oil rates are typical for mainly flying seabirds away from the busiest shipping lanes. A power analysis of the results of beached bird surveys demonstrated the sensitivity of these data as a tool to monitor trends in oil rates of stranded birds. Rather subtle changes in oil rates could be demonstrated, indicating positive results of attempts to protect certain sea areas (e.g. the Wadden Sea) and a decline in oil rates over time.