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Abstract
Large numbers of seabirds may be killed from time to time by individual
incidents of oil pollution, and throughout the year, especially in
winter, dead seabirds, many of them oiled, are washed up on our shores.
These dramatic events have given rise to a great deal of public concern
about the effect of oil pollution on the wellbeing of seabird
populations. It is important to consider this question from the point of
view of population dynamics of seabirds so as to determine whether or
not the observed mortality is substantial and additional in relation to
the natural mortality. Such an approach requires detailed information on
the distribution and numbers of seabirds at breeding colonies and at sea
in their pre-breeding years, in association with their breeding
activities and also in their `wintering' areas. While the data from
breeding colonies provide censuses of breeding birds in defined
geographical areas, movements and dispersal of breeding birds result in
great uncertainty about their distribution and abundance while at sea.
Since many oil polluting incidents, and much of the chronic oil
pollution, affect birds while they are at sea, it is very difficult to
asess the size and the provenance of the populations of various species
that are actually at risk. Some evidence about the numbers of birds
killed by oil and other causes can be obtained from both the beached
bird survey, which are carried out monthly throughout the winter, and
also from the recoveries of ringed birds. These sources of evidence give
rather different results, but both are subject to difficulties of
interpretation. Most seabirds are long-lived, with low mean annual adult
mortality rates, and many of them do not breed until they are several
years old. An attempt is made to relate the numbers of birds found dead,
and the numbers oiled to the numbers that might be expected to die
according to the measured rates of annual mortality. Again there are
very considerable problems in attempting to relate these two sets of
information. However, it seems that in western European waters the
numbers killed by oil pollution is in tens of thousands per winter on
average, while the number expected to die naturally is in hundreds of
thousands per year. It is not known whether or not oil-induced mortality
is additional to natural mortality. It is also pointed out that current
environmental circumstances seem favourable and that the present
resilience of populations may not persist if conditions change. Emphasis
is placed on the very large numbers of pre-breeding birds and the need
for information on the means by which they are recruited to breeding
colonies. Recent monitoring of the numbers of breeding seabirds
throughout Britain shows that most populations are increasing.
... The liquid form of petroleum is commonly named crude oil. Apart from carbon and hydrogen, liquid hydrocarbons contain sulfur, nitrogen, oxygen, metals, and other elements [43] . While the exact molecular composition of crude oil varies within wide limits from formation to formation, the proportion of chemical elements only over fairly narrows limits. ...
... Toward to the end of the eighth decade of the XX-th century it was estimated that as a result of worldwide petroleum exploitation, annually the marine environment was polluted with around 5.5 x 10 6 tons of oil, which was a huge amount compared to submarine seeps that contribute to 0.6x10 6 tons/year. [43] The International Oil Spill Database estimated that between 1960 and 1997 were 732,000 incidents, both onshore and offshore, which have spilled 14 127 000 tons of oil [44] , but in any circumstances many of oil spill incidents are considered minor and are not reported. [45] Also, ITOPF [46] publish yearly statistics and report analyses concerning worldwide sea oil spills Besides, spill data for different part of the world are difficult to compare because each country and producer company follow different reporting requirements based on the volume, type of material, location, and spread of the spill according to national laws. ...
... Plants with two embryonic leaves are termed dicotyledonous ("dicots"). [43] In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct. ...
This work is an interface book between botany and oil pollution, it demonstrates how plants can be used to remedy areas polluted with oil. In this paper the authors
perform a synthesis of data on current global crude oil resources, the amount of
crude oil extracted worldwide, the number of accidents followed by oil and
petroleum products pollution, the types of sources and the effects on affected
soils, water and ecosystems.
Pollution with crude oil and petroleum products is a major global problem.
Although the number of accidental pollution is declining compared to the 1970s,
the risk of accidents due to oil spills is not insignificant. In addition to accidental
pollution, a major problem is historical pollution in which remediation and
reconstruction are much more complicated than in the case of accidental oil
pollution.
This book contains information on the mechanisms of plant reproduction, grow
and propagation, the effects of crude oil and petroleum products pollution on their
multiplication. The role of soil micro-fauna and micro-flora and plants in the
decontamination processes of oil polluted areas by stimulating its degradation is
also analyzed. Were exemplified the plant species more tolerant of the toxic effect
of crude oil compounds and of the film that prevents gas exchanges at the level of
the coat of the seeds and of the cell wall in the seedlings. Also the book contains
information about the seeds of plants that in symbiosis with various mycorrhizae
significantly reduce the effect of crude oil films on the seed coat, favoring the
process of water imbibitions in seed and germination of this. The authors
presented also the important steps of the germination process as the absorption of
water in the seed, initiation of the biochemical and metabolic processes and the
factors that influence the embryo development (temperature, humidity, oxygen,
nutrients). Knowing how plants react in case of accidental oil pollution helps to
select plants that can be used in de-pollution and remediation. The information in
this book allows the formation of an overview in finding simple and inexpensive
solutions for decontamination of oil polluted areas.
... Oil spill pollution plays a significant role in harming marine ecosystems. The presence of oil on the water surface not only reduces populations of marine fauna, but also disrupts the marine food chain (Dunnet et al., 1982). Additionally, oil spills diminish sunlight penetration into the water, thereby limiting the photosynthesis of marine plants and phytoplankton. ...
... Additionally, oil spills diminish sunlight penetration into the water, thereby limiting the photosynthesis of marine plants and phytoplankton. Marine mammals, such as sea otters and seals, are particularly vulnerable to oil spills as their insulating abilities are compromised, making them more susceptible to temperature changes and less buoyant in seawater (Dunnet et al., 1982). Moreover, oil coats the fur of these animals, reducing insulation and leading to fluctuations in body temperature, including hypothermia (Dunnet et al., 1982). ...
... Marine mammals, such as sea otters and seals, are particularly vulnerable to oil spills as their insulating abilities are compromised, making them more susceptible to temperature changes and less buoyant in seawater (Dunnet et al., 1982). Moreover, oil coats the fur of these animals, reducing insulation and leading to fluctuations in body temperature, including hypothermia (Dunnet et al., 1982). Ingestion of oil leads to dehydration and digestive problems (Fingas, 2001;Zeynalova et al., 2009). ...
In recent years, environmental scientists committed to safeguarding the planet have prioritized the detection and monitoring of oil spills in marine waters, a focus expected to persist. Rapid identification of oil spill incidents on the water's surface is crucial for timely monitoring and cleanup efforts, especially to protect the delicate ecology, particularly marine life. Delayed or inefficient response to oil spills exacerbates the adverse impact on marine ecosystems over time. In cases of oil spills in marine systems, swift identification and monitoring facilitate precise cleanup and recovery of hydrocarbons on the water surface. This, in turn, contributes to the preservation of both the marine ecosystem and human lives. The integration of artificial intelligence (AI) in the detection and monitoring of oil spill incidents in aquatic environments holds promise for enhancing the response process to such events. This paper aims to investigate and evaluate the feasibility of employing AI techniques, such as machine learning (ML) and deep learning (DL), to expedite the cleanup and other response operations related to oil spills over water surfaces.
... Although Common Murres are birds highly susceptible to oil pollution, the results are probably applicable to other species with high adult survival rates. [High adult survival rates have been shown for several species that occur in the Southeast, including Northern Fulmar, Manx Shearwater, Herring Gull (Dunnet 1982), andCommon Tern (DiCostanzo 1980). Likewise, high adult survival rates are likely to occur in all Procelliformes and in all species of gulls and terns breeding in the Southeast.] ...
... The adverse effects of oil spill disasters on wildlife populations are highly visible and well documented, often including mass mortalities and widespread oiling of large numbers of individuals (Bourne et al. 1967;Dunnet 1982; Barron et al. 2020). Studies regarding the impacts of oil spills on vertebrate species generally focus on acute effects (i.e., short-term impacts, typically due to initial oil exposure) rather than monitoring potential chronic effects (i.e., long-term impacts that persist after initial oil exposure that may be due to lingering toxins in the environment; Helm et al. 2015). ...
Chronic, long-term impacts of oil spill disasters on wildlife often exceed short-term, highly visible mass mor-talities and widespread oiling of individuals. Species with long lifespans, late maturation, and low recruitment rates are particularly vulnerable to long-term population-level impacts but can be useful as indicator species for ecosystem recovery. In 2010, one of the largest freshwater oil spills in the U.S. occurred in the Kalamazoo River, MI, when 3.2 million L of spilled oil impacted 56 km of river and associated wildlife. During cleanup and restoration efforts in 2010-2011, thousands of northern map turtles (Graptemys geographica) were captured, cleaned, and released. During 2019-2020 northern map turtles were captured to evaluate changes in the population size, demography, and size classes nine to ten years later. Population demography shifts occurred in the first few years after the spill in a species that otherwise exhibits minimal demographic fluctuation under "normal" conditions. In comparing demographic parameters at the time of the oil spill to values ~ 10 years post-spill, a nearly 30% reduction in population size was detected, distribution of body size shifted to smaller males and females, and there was a shift in the population sex ratio between 2011 and 2019. There were also signals of failed recruitment in cohorts that would have hatched during the years immediately before and after the oil spill. These data suggest that beyond the direct mortality caused by the spill, declines in the estimated population size and shifts in the size distribution of northern map turtles are likely indicative of negative demographic impacts incurred following the 2010 oil spill and resulting cleanup.
... These taxa can serve as monitors of marine ecosystems because many species span large geographic ranges, inhabit different coastal and oceanic regimes, and feed on prey at various trophic levels. Changes in species occurrences and abundances, as well as changes in numbers and health of individuals within populations, can indicate changes in temperature, food supply, exposure to environmental contaminants, and other environmental and biological factors [1][2][3]. Seaand shorebird populations are also widely-observed, making them ideal candidates to provide data on community composition and population distributions for biogeographic and macroecological analyses [4][5][6]. ...
The distributions of many sea- and shorebird species span large geographic areas, making them ideal candidates as biomonitors of ecosystem perturbations and long-term environmental trends. The basic question examined in this study was: Does a major open-access data archive contain sufficient temporal- and spatial-scale data to support more detailed inquiry into multi-decadal-scale responses in geographic distributions of specific taxa? The global-scale open-access data platform, Ocean Biodiversity Information System (OBIS), was searched to compile data on bird distributions of the Americas, including the Caribbean Sea. More than 680,000 occurrence records of 210 species, collected between 1965 and 2018, were located and evaluated by marine ecoregion. The Puget Trough/Georgia Basin marine ecoregion, along the United States/Canadian border, and the Virginian marine ecoregion on the US east coast, dominated occurrences, each with more than 100,000 records, while the Gulf of Maine/Bay of Fundy had the most years of records (42). Most records from South America (~29,000) came from the Channels and Fjords of Southern Chile, collected across 16 different years. More than 90% of the recorded data were collected since 1983, and more than 95% of the records were from North American marine ecoregions. We urge additional observations to be shared via OBIS to allow comprehensive large-scale and detailed meta-analyses of spatial and temporal trends in marine and shore-bird communities and their biodiversity.
... In conclusion, oil pollution is still an issue, and we have to stay alert for accidental spills and mismanagement, but the chronic component is much reduced, not only in the North Sea. Seabirds are benefiting from that, whether or not their populations were ever under pressure from the extra mortality induced by oil (Dunnet 1982;Votier et al. 2005). Seabirds benefit, even just from an animal welfare perspective. ...
Marine oil pollution has been an issue of concern for at least a century. The earliest reports contained outrage over oil-contaminated dead seabirds found ashore. This paper reports on observed trends in strandings and oil rates of Common Guillemots Uria aalge to illustrate the history of oil pollution and its effects in the North Sea. This paper is also a tribute to Peter Hope Jones, who brought systematic beached bird surveys and oil-spill impact assessments to a higher level, by implementing detailed research on affected wildlife. In recent decades, unexpectedly, the oil problem has disappeared almost completely from the North Sea. Given the global nature of current environmental issues, including the climate and biodiversity crises, it may be instructive to examine the background to this stunning success. A short history is presented, including the measures taken to reduce the oil problem. It required a succession of major oil incidents to push the community into action. The process of international conventions was notoriously slow, and the implementation of concrete measures even slower, as economic arguments prevailed to prevent or delay immediate action.
... The adverse effects of oil spills on wildlife populations are highly visible and well documented, from the oiling of large numbers of individuals to direct oil exposure mortalities (Dunnet, 1982;Barron et al., 2020;King et al., 2020). Emergency response to oil spills generally includes rescue of oiled wildlife in the first days to weeks following a spill, rehabilitation of oil-exposed animals, or collection of individuals that died (Jessup, 1998). ...
Rehabilitation is often used to mitigate adverse effects of oil spills on wildlife. With an increase in production of alternatives to conventional crude oil such as diluted bitumen (dilbit), emergency spill responders and wildlife rehabilitators need information regarding the health and survival of free-ranging vertebrates exposed to dilbit under natural conditions. In 2010, one of the largest freshwater oil spills in the United States occurred in the Kalamazoo River in Michigan, when over 3.2 million liters of spilled dilbit impacted 56 km of riverine habitat. During 2010 and 2011 cleanup efforts, thousands of northern map turtles (Graptemys geographica) were captured from oiled stretches of the river, cleaned, rehabilitated, and released. We conducted extensive mark-recapture surveys in 2010, 2011, and 2018–2021, and used this dataset to evaluate the monthly survival probability of turtles 1–14 months post-spill and 8–11 years post-spill based on whether turtles were temporarily rehabilitated and released, overwintered in captivity and then released, or were released without rehabilitation. We found that rehabilitated or overwintered turtles had a higher probability of survival 1–14 months post-spill than non-rehabilitated turtles; however, 8–11 years post-spill the among-group differences in monthly survival probability had become negligible. Additionally, following the oil spill in 2010, nearly 6% of northern map turtles were recovered dead, died during rehabilitation, or suffered injuries that precluded release back into the wild. Our results demonstrate that exposure to dilbit in free ranging turtles causes direct mortality, while effort spent on the capture and rehabilitation of oiled freshwater turtles is important as it increases monthly survival 1–14 months post-spill.
... The adverse effects of oil spills on wildlife populations are highly visible and well documented, from the oiling of large numbers of individuals to direct oil exposure mortalities (Dunnet, 1982;Barron et al., 2020;King et al., 2020). Emergency response to oil spills generally includes rescue of oiled wildlife in the first days to weeks following a spill, rehabilitation of oil-exposed animals, or collection of individuals that died (Jessup, 1998). ...
... Many hydrocarbon components in crude oil are toxic and have a certain degree of water solubility. Oil pollution poses many risks to wildlife, human health, and soil durability [7]. ...
This study focuses on studying the impacts of residues oil on the geotechnical properties of soil and the performance of raft footing rested on oil contaminated soil and subjected to vertical loads. The contaminant used in the present study is residues oil, which is by product disposed of diesel engine oils. The soil samples are contaminated artificially by soaking with two percentage of disposed engine oil of contaminant consist of (disposed engine oil and gasoline) of 20% weight of dried of intact soil samples to obtain different concentrations of contaminant absorbed by soil samples for 30 days to complete the saturation. The mechanical model manufactured to investigate the behavior of raft footing under vertical static loading rested on intact and contaminated soils. The obtained results detected contaminant content have notable impacts on the physical soil characteristics such as the fine particles, specific gravity, plasticity index, and maximum dry unit weight decreased with the increase of contaminant content than that of intact soil. The mechanical soil properties of soil indicated the increase of the compressibility of soil with increase of residues oil percentage, but the soil strength and stiffness are decreased notably. In addition, the total and permanent settlement of raft footing constructed in contaminated soil samples increased by (27-43) % and by (41-58) % than that of an intact soil sample, respectively.
... Short-term toxicity in fishes includes lymphocytosis, epidermal hyperplasia, haemorrhagic septicaemia (Beeby, 1993), whereas in mammals, it possesses an anticoagulant potency (Onwurahet et al., 2002). It was estimated that some tens of thousands of seabirds were killed as a result of spilled oil in sea (Dunnet, 1982). ...
Bacterium Ralstonia pickettii has ability to survive and thrive in low nutrient condition as well as a capability to remediate some pollutants and using them as carbon and energy source. In this study, the ability of R. pickettii on biodegradation of crude oil under high salinity medium was investigated. R. pickettii was pre-incubated in nutrient broth (NB) medium and then, washed and transferred to artificial seawater medium. Crude oil was added to each culture and incubated for 7 and 14 days. The biodegradation of crude oil was analysed using Gas chromatography mass spectrometry (GC-MS). The result showed that R. pickettii had successfully degraded the crude oil in the high salinity artificial seawater. The incubation on 7 and 14 days did not show a significant effect on the number of the degraded compounds. The optimum recovery percent was obtained from the derivation of 2,6,10,14-tetramethyl hexadecane with the recovery percentage of 12.7% and 16.0% for 7 and 14 days respectively. This study indicates that R. picketti can be potentially used for bioremediation of crude oil under high salinity environments.
... There are various reasons which can be considered as the main amplifiers for the contamination of oil leaking. Spoiling of tanks and pipes and different wars among nations can extend this issue in the world (Dunnet 1982). Furthermore, it has been proven most oil products, especially gasoline, contain a wide range of heavy metals like lead (Pulles et al. 2012). ...
Various laboratory tests were carried out to study the effects of lead and gasoline on the geotechnical properties of three kinds of contaminated soil. This paper addresses soils contaminated with lead, gasoline, and lead-gasoline. This work aimed to investigate the critical alterations in geotechnical properties of an artificial soil (MDD: 17.6 kN/m³) due to these contaminants ‘ simultaneous application. For this purpose, soil samples were prepared with several lead contents (1000, 2000, 5000, 10000, 20000 ppm) and different gasoline contamination percentages (the 3%, 6% and 9% weight of dried soil) with the 4 days contamination duration. The tests conducted were: compaction, permeability, direct shear test, unconfined compressive strength, X-ray diffraction, and SEM analysis. The results indicated increment in maximum dry density and internal friction angle with the increase in the amount of lead and gasoline in all types of samples. The growth in maximum dry density was higher with gasoline than lead contamination. Also, by increasing lead content in contaminated samples the values of cohesion and hydraulic conductivity increase while a reverse trend was observed with the climb in gasoline content. Furthermore, Lead-gasoline contaminated samples show a peak behavior for both unconfined compressive strength and failure strain by an increase in pollution content.
... Attributing seabird population changes from oiling can be difficult without pre-spill baseline data, needed to separate estimates of mortality due to oiling from mortality due to environmental fluctuations, other sources of mortality, emigration and recruitment (e.g., Dunnet, 1982;Crawford et al., 2000). The numbers of penguins oiled in some of the largest historical oil spills, however, provide evidence that these events can have significant population level impacts ( Table 2). ...
Penguins face a wide range of threats. Most observed population changes have been negative and have happened over the last 60 years. Today, populations of 11 penguin species are decreasing. Here we present a review that synthesizes details of threats faced by the world’s 18 species of penguins. We discuss alterations to their environment at both breeding sites on land and at sea where they forage. The major drivers of change appear to be climate, and food web alterations by marine fisheries. In addition, we also consider other critical and/or emerging threats, namely human disturbance near nesting sites, pollution due to oil, plastics and chemicals such as mercury and persistent organic compounds. Finally, we assess the importance of emerging pathogens and diseases on the health of penguins. We suggest that in the context of climate change, habitat degradation, introduced exotic species and resource competition with fisheries, successful conservation outcomes will require new and unprecedented levels of science and advocacy. Successful conservation stories of penguin species across their geographical range have occurred where there has been concerted effort across local, national and international boundaries to implement effective conservation planning.
... Generally, the biological risk induced by oil or its derivates is more severe in these environments because they are important sites for the reproduction, breeding, and feeding of diverse oceanic species (Botello et al., 2005). It was estimated that some tens of thousands of seabirds were killed as a result of oil spilled at sea (Dunnet, 1982). Dying mangrove trees, tarred beaches, and declining fish catches, all seem to be threats to long-term viability of some ecosystems. ...
The abundance of certain spionid species can be closely linked to environmental disturbances producing quantifiable changes in community structure. We hypothesize that in stress conditions, the spionids would tend to localize in the upper level of the sedimentary column near to the sediment–water interface. The aim of this work was to analyze, through an ex situ experiment, the effect produced by two concentrations of crude oil on the spionids at different depths of the sedimentary column and identify possible pollution indicators. A simulated oil spill at two input levels was carried out in the laboratory for 30 days. The effect of the adding of crude oil was significant only in the superior level of the sedimentary column. The differences in the abundance between levels by experimental conditions were significant in all the cases. Sensitive species like Scolelepis (Parascolelepis) sp. and Rhynchospio glutaea disappeared while other species like Boccardia proboscidea had a higher resistance to the addition of crude oil. This study constitutes the first characterization of spionid assemblages of the Patagonian coasts altered by crude oil in sediments, and the first identification of species, which can be useful pollution indicators.
... In mammals it possesses an anticoagulant potency [7]. It was estimated that some tens of thousands of seabirds were killed as a result of spilled oil in sea [8]. Dying mangrove trees, tarred beaches and declining fish catches, all seem to be threats to long term viability of some ecosystem such as the Niger Delta areas of Nigeria [9]. ...
The scope of this study was to enumerate and identify microorganisms present in crude oil polluted soil before and after remediation with Eudrilus eugeniae using conventional method for enumeration and molecular tools (ITS 1 and ITS 4 primers) for identification. A crude oil polluted soil from Khana Local Government of Rivers State Nigeria and also soil from botanical garden of the University of Lagos were used. These soil samples were measured in four different concentrations (25%, 50%, 75% and 100%). Each of these concentrations was experimental setup of addition of substrate alone, E. eugeniae and
substrate and E. eugeniae alone. These setups were made in triplicate amounting to a total of thirty six
experimental setups. Enumeration of microbial load was done before and after addition of each of the
content of the experimental setups using conventional method and then identification of microbes was done using molecular tools. The result shows total heterotrophic fungi was 2.9 x 104 cfu/m/g, while the
total heterotrophic bacteria was 4.4 x 105 cfu/m/g before remediation. After remediation, total heterotrophic fungi was 1.6 x 105 cfu/m/gwhile total heterotrophic bacteria was 5.0 x 104 cfu/m/g. This shows that microorganisms were present in the soil before and after remediation. The increase in number of microbes suggests a favorable condition for continuity of microbial life. Fungi such as Trichoderma asperellum, Aspergillus flavus, Penicillum chrysogenum and another strain of Aspergillus flavus were identified. The bacteria sequencing failed suspected to be due to primers used or error with
sequencing plates. In conclusion, the results of this study confirmed the presence of microorganisms in
crude oil polluted soils. The enumeration and identification of the bacteria and fungi in this experiment
will help to enhance in situ clean-up of crude oil polluted soil.
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... Fisheating birds, often at the top of food chains, are vulnerable to oil because it can cause mortality, foraging difficulties, and lowered reproductive success (Piatt et al. 1990). Chronic, episodic, or acute oil spills may cause acute or chronic mortality (Dunnet 1982;Hunt 1987;Burger 1997a), including oil discharges that affect marsh or island structures where birds nest (McCauley and Harrel 1981;Mendelssohn et al. 2012;Fraser et al. 2006). Effects of oil on individual birds have been demonstrated in dose-dependent field and laboratory experiments, as well as from field observations (Burger 1994(Burger , 1997bLance et al. 2001;Payne et al. 2008). ...
The Deepwater Horizon oil spill (2010) could have affected the behavior and productivity of birds nesting along the Gulf of Mexico. This research examined the productivity of several species of colonial waterbirds in 2011 in LA colonies that were classified according to the M252 peak SCAT shoreline map oiling designations (as of April 6 2011) within 2 km of each colony. Colonies were classified as no oil, little oil, or medium to heavy oil. Because of the uneven distribution of oil and variation in bird composition within colonies, not all species occurred in each of the three oiling classes in the LA colonies studied. I tested the following hypotheses: (1) there were no interspecific differences in nesting phenology, (2) there were no differences in the number of species per colony as a function of oiling, and (3) there were no differences in reproductive measures as a function of oiling. Nesting phenology differed among species, with brown pelicans (Pelecanus occidentalis), great egrets (Ardea alba), and tri-colored herons (Egretta tricolor) nesting earlier than the other species. There were no significant differences in the number of species nesting in colonies as a function of oiling category. Along LA’s shoreline, nests in colonies with a “no oil” category within 2 km of the colony had similar or lower maximum number of chicks/nest, than those from birds in colonies designated as light or moderate/heavy oiling. Average maximum chick sizes in nests in colonies designated as no oil were either similar to or smaller than chicks in nests in colonies designated as either category of oiled. The data suggest that in the year following the oil spill, there were no differences in reproductive success. Although long-term studies are essential to determine effects on population dynamics, the continued exposure of birds nesting along the Gulf of Mexico to acute and chronic oil sources make this a nearly impossible task.
... Oil contributes to foraging difficulties, lowered reproductive success, and mortality, especially in seabirds (Piatt et al. 1990). The effects of oil discharges could be acute (mortality) (Dunnet 1982;Hunt 1987;Burger 1994aBurger , 1997aLance et al. 2001;Payne et al. 2008;Wiens et al. 1996), or chronic, including the effects from operational oil discharges that affect marsh structure (McCauley and Harrel 1981;Mendelssohn et al. 1990;Fraser et al. 2006). Effects of oil include cessation of growth in chicks, osmoregulatory impairments, hypertrophy of hepatic, adrenal, and nasal gland tissue (Miller et al. 1978), reduced thermoregulation (O'Hara and Morandin 2010), reduced survival of chicks (Trivelpiece et al. 1984), and changes in hematology and blood chemistry (Newman et al. 2000). ...
Fifteen indicator species with different lifestyles and behavioral patterns are used to examine the health of the Gulf avifauna before the Deepwater Horizon accident. There are 395 bird species recorded for the Gulf, and 31 % occur along all coasts of the Gulf. The highest avian diversity is along the Mexican Gulf Coast. A high proportion of the US nesting population of Reddish Egret, Sandwich Tern, Black Skimmer, Royal Tern, Forster’s Tern, Laughing Gull, Snowy Plover, and Roseate Spoonbill occur along the Gulf. Several seabirds (boobies, frigatebirds) nest primarily on the Campeche Banks in the southern Gulf of Mexico. Habitat loss, due to both anthropogenic and natural causes (sea level rise, erosion), is the primary threat facing birds in the Gulf of Mexico, followed by predators, human disturbance, high tides, storm tides, and other weather-related events. Loss of habitat is most severe at the land margin, where the land meets the sea. Pollutants have affected behavior and populations of birds in the Gulf although to a far lesser degree than habitat loss and modification. Oil can cause immediate mortality and chronic injury, but it has not been demonstrated to permanently affect any populations of birds in the Gulf. Plastics and fishing lines cause mortality, particularly in seabirds foraging in the Gulf.
... There has been a long, world-wide history of oil spills and associated mortality of marine wildlife (Dunnet 1982, Clark 1984, NRC 1985, Clark 2001. Despite recent declines in the amounts of oil released or spilled into the marine environment, chronic oil pollution is still a reason for concern (Camphuysen 2007), and within the European Union, major accidental oil spills (>20 000 tonnes) still occur at irregular intervals (European Environment Agency 2001. ...
ABSTRACT: Technical online documentation of the approach in case of a wildlife response during major oil spills, Available online www.oiledwildlife.eu
... There has been a long, world-wide history of oil spills and associated mortality of marine wildlife (Dunnet 1982, Clark 1984, NRC 1985, Clark 2001). Despite recent declines in the amounts of oil released or spilled into the marine environment, chronic oil pollution is still a reason for concern (Camphuysen 2007), and within the European Union, major accidental oil spills (>20 000 tonnes) still occur at irregular intervals (European Environment Agency 2001, 2004). ...
Technical online documentation of the approach in case of a wildlife response during major oil spills, Available online www.oiledwildlife.eu
... In fact, several scientists have played down the population level effects of oiling, simply because most seabird populations have increased over the past 100 years. Severe population effects were anticipated (Bergman 1961, Goethe 1968, Bourne 1971, Baillie & Mead 1982, but were seldom proved (Dunnet 1982, Clark 1984, Dunnet 1987. Sometimes the effects were simply much smaller than expected, due to unforeseen factors such as unusual weather and the type of oil involved (Osborn 1996, Heubeck 1997a). ...
This report reviews recent trends in oil pollution, with emphasis on ‘chronic oil pollution’ in European waters. Chronic oil pollution is the result of the continuous stream of smaller and larger oil spills and deliberate / illegal “operational” discharges of oily waste from vessels. This pollution is chronic vs. episodic in that recurring oil discharges in a sensitive area prevent the impacted resources from recovering. It is a diffuse type of contamination from various sources that enters the environment in gaseous, liquid or solid forms.
The most lethal form enters the marine environment through deliberate (illegal) discharges at sea. The most visible effect of marine oil pollution is the associated mortality of marine wildlife, notably seabirds. This report describes the scale and identifies the sources of the oil pollution problem. It discusses the methods of assessing the impact on marine wildlife and outlines the species-specific and area-specific differences in sensitivity to oiling. Chronic oiling is a constant threat to seabirds. Legal measures to reduce the oil problem are reviewed and considered in the context of recent trends indicating a decline in the proportion of stranded seabirds showing traces of oil contamination. Rather than simply signalling the issue of chronic oil pollution, the concluding comments of the report propose possible solutions and review ideas to further reduce the problem.
Chronic oil pollution as an issue
• Worldwide annual releases of oil have declined since the early 1970s from approx. 6 million tons to about one million tons, but a general lack of information prevents a thorough evaluation of true current levels of oil pollution at sea.
• Illegal and incidental operational discharges from shipping and offshore installations (chronic oil pollution) are the most important sources of marine wildlife casualties because they occur all the time and because of the important overlap between large seabird concentrations and busy shipping lanes.
• It is a misconception that large spills cause greater environmental damage than small spills: what matters are when and where the release happens and the type of oil that is spilled.
• Seabirds are particularly vulnerable to oil because this substance damages the insulating properties of their plumage, which they require to survive in a maritime environment.
• Seabirds that spend most of their time afloat and that have little contact with the coast are the most vulnerable to oil pollution.
• Small amounts of oil in the plumage cause a bird to give up feeding and most casualties are due to starvation.
• Large amounts of oil on the plumage cause instant immobility and possibly immediate death through suffocation and drowning.
Measuring the scale and impact of chronic oil pollution
• Beached-bird surveys have been routinely conducted in many European countries over the past decades, enabling a proper historical evaluation of temporal trends in marine oil pollution.
• Oil rates in seabirds found dead on beaches are highest in areas bordering shipping lanes.
• Significant declines in oil rates have been found over the past 30 years.
• Aerial surveys are an instrument to measure oil pollution more directly and the results confirm that most oil slicks are formed in the vicinity of the major shipping lanes. These surveys have generally confirmed the declining trend of oil slick occurrence, but long-term comparable data are not readily available for analysis.
• Recent technology offers the possibility to detect oil slicks from space. This technology is particularly promising for the future, but long-term trends cannot be deduced from these data at the moment.
• Despite good intentions and collaboration from different countries, an international overview of oil pollution is impeded by difficulties in harmonising the available data. Recent initiatives by the EC Joint Research Centre to develop standard nomenclature and an on-line database are described.
• OSPAR introduced a series of Ecological Quality Objectives to monitor characteristic parameters in the marine environment. EcoQOs are intended to act as monitoring guidelines until a set target has been reached.
• The oiled-guillemot EcoQO, soon to be implemented, is intended as an instrument for monitoring chronic oil pollution in 15 European sub-regions. The objective of this particular EcoQO is defined as follows: “The average proportion of oiled common guillemots should be 10% or less of the total found dead or dying in each of 15 areas of the North Sea over a period of at least 5 years. Sampling should occur in all winter months (November to April) of each year.” We would expect that this will motivate the development and
implementation of similar monitoring tools (and policy targets) in other parts of Europe. Chronic oil pollution in Europe
• The sources of chronic oil pollution are diverse and estimates of total quantities vary widely.
• Two aspects deserve attention: oil pollution has declined over the past decades, but illegal discharges by vessels are still a major source of the chronic oil pollution currently observed.
• The EC JRC oil spill database, presented on the web at http://serac.jrc.it/midiv/, is consulted to evaluate recent developments in chronic oil pollution. Composite maps of the Special Areas within Europe (the Black Sea, the Mediterranean, the Baltic and the North Sea) show the locations of nearly 20,000 oil slicks detected over a period of six years (only three years in some areas).
• The recent data from high tech remote sensing equipment provide a very clear signal that European waters are by no means free of oil spills.
Sensitive species, sensitive areas
• Oil Vulnerability Indices (OVI) are widely used to rank species in terms of vulnerability to oil. Important parameters are behaviour, exposure, biogeographical population, reproductive potential, and reliance on the marine environment. OVIs should preferably be calculated at the subspecies level.
• OVIs have not been calculated for numerous European taxa of seabirds. in the (wintering) distribution of seabirds should be taken into consideration with regard to the vulnerability of certain areas, and a deeper
understanding of offshore habitat requirements is therefore needed.
• The Greenland Sea, Icelandic waters, Bay of Biscay, Portuguese and Spanish Atlantic coasts, Macaronesia, the Mediterranean and the Black Sea are data-deficient in terms of knowledge regarding their sensitivity to oil pollution.
• Knowledge pertaining to the sensitivity of the Barents Sea, Norwegian Sea, Channel and Celtic Sea is partly data-deficient.
• The North Sea, Irish Sea, waters west of Britain, Faeroese waters and the Baltic Sea are well studied and their sensitivity to oil pollution has been evaluated. The effects of chronic oil pollution on seabird populations
• The effects of oil spills on seabirds have often been exaggerated in the past.
• Adequate surveys, coupled with drift experiments and accurate information on the age structure of oil spill casualties and their possible (breeding) origin are required to enable a proper evaluation of the scale and impact of accidental or chronic oil pollution on seabirds.
• Oil pollution is a major threat to seabirds mainly in their European wintering areas.
• Direct effects on seabird populations, such as on survival rates and age structure, are rarely detected because specific long-term studies involving individually marked birds need to be in place in the area affected by the spill before it actually happens.
• A recent review of major oil spills revealed that adequate data usually have been collected but those post-spill evaluations making use of that data tend to be rare.
• Recent studies showed that winter mortality of adult guillemots was doubled by major oil pollution incidents, demonstrating that oil pollution can have wide-scale impacts on marine ecosystems, and that these impacts can be quantified using populations of marked individual seabirds.
Law and programs to reduce levels of oil pollution, and minimising the effects of spills
• The UN Convention for the Law of the Sea (UNCLOS) has recognised pollution from vessels as one of the main threats to the marine environment. In response, UNCLOS has established the framework for the multi-lateral development of rules and standards acting mainly through the competent international organization, namely the International Maritime Organization (IMO). The IMO has adopted several instruments to control the
environmental impact of shipping, the most important being the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78).
• Within Europe, “Special Areas” have been identified under MARPOL (Annex I) as waters where oil discharges are essentially illegal. Special Area status within Europe was applied to the Mediterranean, Black, and Baltic seas in 1978. The marine region corresponding to North West European waters (mainly the North Sea) was designated as a Special Area in 1999.
• The designation of Special Areas under MARPOL is a significant step, but without enforcement, such legislation is pointless. highlighted above.
• Several recent studies based on evidence from offshore surveillance by “coastal” states and from inspections by Port States show that one of the basic problems lies with a relatively small percentage of vessels and owners that persist in consistently operating their vessels in full contravention to the IMO's body of environmental regulations. In relative terms, the numbers are small – approximately 10-15% of the world fleet. However, in absolute terms, this subset of owners accounts for a large number of vessels.
• Oily waste discharge standards have been circumvented by companies and ships’ crew. There is evidence that the standards themselves foster these circumventions as the pollution prevention equipment is often poorly maintained of insufficient capacity and does not operate as designed.
• In March 2006, the Marine Environmental Protection Committee (MEPC) of the IMO has invited member governments to provide concrete proposals, including draft MEPC circulars or proposed amendments to existing instruments, to address the operational problems most vessels are facing and what may the root causes of non-compliance.
Conclusions
• Although a general decline has been observed in marine oil pollution, there is also a shortage of long-term studies and of readily available and comparable information, which limits our understanding of the true impacts of oil pollution on marine wildlife and on seabird populations in particular.
• Available knowledge seems to play very little part in orienting the decision in the planning of clean-up operations in the aftermath of oil incidents or in planning aerial surveillances of oil at sea.
• The recently established EC website and JRC database clearly show that many instances of oil pollution are in fact avoidable, but even in Special Areas control measures have been inadequate to reduce and eliminate illegal spills. If illegal discharges are still as frequent as shown, states need to adopt far stricter systems of Port States and Flag State control, as well as effective monitoring and sanctioning procedures.
• Increased enforcement, however, is only a partial and for many countries a costly solution.
• Apart from the shortcomings in existing legislation and enforcement for preventing oil spills and illegal discharge of oil in sensitive sea areas such as MARPOL Special Areas and PSSAs, there is also a technical limitation in that the ecological criteria used to designate such areas fail to specifically address seabird sensitivity to oil as indicated by current data on seabird distribution and seasonal movement patterns.
... With the term surface pollutants, a wide range of lipophilic substances is covered, including mineral oils, vegetable oils and various chemicals. Mineral oils pose by far the greatest threat to seabirds in the North Sea (Barclay-Smith, 1931;Bourne, 1968;Dunnet, 1982;Camphuysen, 1989;Heubeck, 1995;Camphuysen, 1995Camphuysen, , 1997Camphuysen, , 1998, but several incidents with other substances have shown the equally lethal effects of many products (Anonymous, 1975;Swennen, 1977;McKelvey et al., 1980;Engelen, 1987;Timm and Dahlmann, 1991;Rozemeijer et al., 1992;Scholten, 1993;Dahlmann et al., 1994). In The Netherlands, chronic oil pollution is a constant threat to seabirds and oil rates among stranded birds are very high in comparison with those in other West European countries (Furness and Camphuysen, 1997;Camphuysen, 1998). ...
This paper reports on a mass stranding of seabirds in the North Sea in December 1998. Hundreds of birds washed ashore alive in Zeeland (SW Netherlands), covered in a whitish, sticky substance, and were transported to a rehabilitation centre. About 10 days later, more (dead) casualties washed ashore further to the north on Texel and along the mainland coast, again covered in a glue-like substance. Common guillemots Uria aalge, northern fulmars Fulmarus glacialis and common scoters Melanitta nigra were the most numerous birds affected in this incident. Both strandings were temporarily (10 days) and geographically separated (ca. 120km apart), but were apparently caused by a single source of pollution. At least 1100 seabirds were affected by this substance, soon identified as polyisobutylene (C4H8). PIB is known as a non-toxic, non-aggressive substance. However, volunteers cleaning the birds in the rehabilitation centre reported serious discomfort and dizziness. Moreover, the soft parts of the birds found dead (bill, eye, throat, feet, webs) appeared to dissolve in the substance in a few days time. Although the dumping of PIB in the marine environment is not explicitly prohibited under MARPOL, the effects on wildlife are sinister enough to plea for counter-measures.
Conclusions: The lethal effects of non-mineral oils and other fatty substances on seabirds have been clearly illustrated in several mass-strandings in recent years. While several of these substances are legally dumped into the marine environment, they may be equally harmful to marine wildlife as mineral oils for which rigid counter-measures were effectuated under MARPOL. The effects of most discharges of chemicals remain unnoticed, because very few samples are routinely taken and adequately analysed by expert laboratories. We advocate a more stringent beached bird survey programme, coupled with a systematic sampling programme of substances on beaches and beached birds. The chemical analysis of feather samples would provide crucial further insight into the types and effects of surface pollutants responsible for the death of seabirds and other marine wildlife.
... Oil pollution of the seas was recognized as a problem in the first half of the 20th century and various countries introduced national regulations to control discharges of oil within their territorial waters (Mörzer Bruijns & Brouwer 1959, Dunnet 1982, 1987. The International Convention for the Prevention of Pollution from Ships and recent amendments meant to reduce the scale and impact of chronic oil pollution worldwide. ...
This is the annual update for OSPAR of the beached bird survey (BBS) results in The Netherlands (winter 2012/13). The Dutch BBS provides data for OSPAR area's 8, 9 and 10, but data from Belgian and German colleagues will have to be merged to arrive at the final values for these areas. For the Dutch North Sea region, significant declines in oil rates were reported over a long study period (1977/78-2012/13) as well as over the last 15 years. Declines were found in offshore seabirds (Common Guillemots (1998-2013; P< 0.05), Razorbills (P< 0.01) and Black-legged Kittiwakes, P< 0.01) as well as in most nearshore species (Common Eider, 1998-2013 P<0.05, Herring Gull, P<0.01). For coastal Common Scoters, the declining trend was just not significant, partly as a result of small sample size in recent years (1998-2013 P>0.05). The arithmetic 5-year running mean for Common Guillemots found along the Dutch North Sea shoreline has currently arrived at c. 30-35%. Data tables are provided to calculate running means for OSPAR areas 8, 9, and 10 (after a data merge with additional Belgian and German datasets). In winter 2012/13, densities of birds washing ashore were rather low and with low densities of stranded birds. In future years, a somewhat higher observer effort is required in order to guarantee a sufficiently large sample of birds to be checked for the presence or absence of oil.
... Oil pollution of the seas was recognised as a problem in the first half of the 20th century and various countries introduced national regulations to control discharges of oil within their territorial waters (Mörzer Bruijns & Brouwer 1959, Dunnet 1982, 1987. The International Convention for the Prevention of Pollution from Ships and recent amendments meant to reduce the scale and impact of chronic oil pollution worldwide. ...
... Because spilled oil usually does not persist in a toxic state for long periods of time (Neff and Stubblefield have minimal consequences on population dynamics, especially for long-lived marine organisms such as seabirds (Dunnet 1982, Ford et al. 1982. ...
Oil spills may affect species through direct effects on population size and structure and direct and indirect (toxicological) effects on reproduction. Spill effects on the habitats these organisms occupy have received less attention, but they are no less important. For 2.5 yr following the Exxon Valdez oil spill in Prince William Sound, Alaska, we studied the use of oil-affected habitats by 42 species of marine-oriented birds. On 11 survey cruises, we surveyed bays that had received different levels of initial oiling. We related the abundance of individual species in the bays to the oiling gradient, using regression models that included habitat measures to control for variations among the sites in features other than oiling level. We defined a spill-induced impact as a statistically significant relationship between the abundance of a species and values along the oiling gradient, after accounting for the effects of variations in habitat features. We used among-year comparisons of regressions between oiling levels and abundance, controlled for season, to assess recovery. We concluded that recovery from a spill-induced impact had occurred when we no longer could detect a significant relationship between a species' abundance and oiling levels. Overall, 23 (55%) of the 42 species exhibited no initial negative impacts on their use of oil-affected habitats. Of the 19 species that did exhibit negative impacts, 13 (68%) showed evidence of recovery within 2.5 yr (the final survey in 1991). Six species (Horned Grebe, Red-necked Grebe, Barrow's Goldeneye, Bufflehead, Mew Gull, and Northwestern Crow) showed no clear evidence of recovery by our final survey. The proportion of species recorded on individual surveys that exhibited negative impacts at that time declined over the study, from 54% on the first survey after the spill in 1989 to 10% in late 1991. A principal components analysis revealed extensive ecological overlap between species that were negatively impacted in their use of oil-affected habitats and those that were not. The six species that had not recovered by late 1991 tended to be intertidal feeders and residents, but these traits also characterized some species that did not exhibit initial impacts and some species that subsequently recovered from impacts. We detected no obvious ecological differences between species that suffered spill impacts on habitat use and those that apparently were not affected, or between impacted species that later recovered in their use of habitats and species that had not yet recovered. These results indicate that the Exxon Valdez oil spill had clear initial negative impacts on habitat use by nearly half of the species examined, suggesting substantial initial effects on habitat suitability for these species. These impacts persisted for <2.5 yr for most affected species. This rate of recovery in habitat use parallels the rapid recovery (usually <2 yr) documented for other oil-affected communities (e.g., intertidal invertebrates, fishes, and birds) that have been studied in Alaska and elsewhere.
... Hér er aðeins unnt að nefna örfáar, t.d. GESAMP (1977), Andrews og Standring (1979), Dunnet (1982), Hope Jones o.fl. (1978), Mosbech (2000), Wiese (2002) og Peterson o.fl. ...
... Nonetheless, effects of such "wrecks" on nearby breeding colonies are not always evident (Bailey andDavenport 1972, Harris andWanless 1984). These observations suggest that seabird population dynamics may be played out over very large spatial scales: because of dispersal, movement of individuals among breeding or wintering locations, and the existence of large pools of "floating" (literally) individuals, the effects of localized perturbations may be buffered or diffused over regions much larger than the immediate spill area (Dunnet 1982, Klomp and Furness 1992, Wooller et al. 1992, Wiens 1995. ...
The supertanker Exxon Valdez ran aground on 24 March 1989, spilling 41 X 10(6) L of oil into Prince William Sound, Alaska. To examine effects of this oil spill on the marine bird community, we analyzed data from 11 survey cruises between June 1989 and August 1991. Cruises were conducted in 10 study bays differing in the magnitude of initial oiling. We gauged bird responses to the spill in terms of habitat use, measured by frequency of bay occupancy and species abundances as functions of initial bay oiling. We focused on community-level measures to obtain a broader perspective than can be obtained from studies directed toward individual species of concern. Effects of the oil spill on community measures were most apparent shortly after the spill but diminished rapidly. Species richness was significantly lower in 1989 than at the same season 1-2 yr later, especially in heavily oiled bays. Species diversity (log-series alpha) was also significantly reduced in more heavily oiled bays in early summer 1989 and 1990, but impacts evident in midsummer and fall 1989 were absent 1 yr later, and there were no significant relationships between diversity and bay oiling after midsummer 1990. Species occurrence in bays was more restricted immediately following the spill than 1-2 yr later, and widespread species were less abundant in early summer and fall 1989 than at the same seasons 1 yr later. This latter pattern was reversed in the midsummer surveys, perhaps because spill clean-up activities attracted large numbers of nonbreeding gulls. We used cluster analysis to define six avian guilds based on ecological characteristics of the species. Species richness of several guilds of birds feeding on or close to the shoreline was negatively related to initial oiling level until early or midsummer 1990, but not thereafter. Of these guilds, the richness of a guild of winter visitant and resident species showed the greatest negative association with initial oiling. However, the richness of guilds of solitary or colonial species that dive and/or feed on fish showed no significant relationships with oiling at any time. Correspondence analysis based on bird community composition indicated clear differences between heavily oiled and unoiled bays in 1989, but overall community composition converged between these sets of bays in subsequent years. Our analyses indicated that the Exxon Valdez oil spill had significant initial impacts on marine bird community structure, although they were not evenly distributed among ecological guilds. Even during the first survey, many species were present in the most heavily oiled bays. Although a few species continued to show spill impacts in late 1991, none of the community measures indicated continuing negative oiling effects. This suggests that, at the community level, recovery was well underway, consistent with observations that seabird habitat had apparently returned to normal in all but a few localized areas by mid-1991. Seabird communities appear to have considerable resiliency to such severe but relatively short-term perturbations, possibly because birds move over a regional scale. It may, therefore, be important to consider regional processes in evaluating recovery following environmental accidents.
... Estimates of total mortality resulting from oil spills are thus often imprecise ( Piatt et al. 1991). Even where total mortality is accurately estimated, it is generally difficult to demonstrate that these losses, and the associated impacts, have contributed towards changes in the population, either because of the lack of reliable pre-and post-spill data or because of the difficulty in separating oil mortality from other factors, such as environmental variability, natural mortality, recruitment, immigration and emigration, and other sources of anthropogenic mortality ( Dunnet 1982, Wiens 1996, Agler et al. 1999). De-oiling contaminated seabirds has generally been viewed as an animal welfare issue, with little conservation value. ...
... Seabirds are one of the worst affected organisms in such events, and substantial numbers of seabird carcases have been recorded immediately and in the subsequent months following major oil spills around the globe [2,3]. Prior to the Exxon Valdez oil spill, it was thought that impacts to seabirds derived exclusively from acute mortality [4], with no apparent effects at population level [5]. Research after this spill has challenged this traditional view, suggesting that the effect of oil spills may be complex and long-lasting due to, inter alia, ecosystem-driven effects [6]. ...
Large oil spills are dramatic perturbations on marine ecosystems, and seabirds are one of the worst affected organisms in such events. It has been argued that oil spills may have important long-term consequences on marine organisms, but supporting evidence remains scarce. The European shag (Phalacrocorax aristotelis) was strongly impacted at population level by the Prestige oil spill, the biggest spillage in the eastern North Atlantic. In this paper, we report on the long-term consequences on reproduction of this coastal seabird, using temporal and spatial replicated data (before-after-control-impact design). Our study revealed long-term reproductive impairment during at least the first 10 years since the Prestige oil spill. Annual reproductive success did not differ before the impact, but after the impact it was reduced by 45% in oiled colonies compared with unoiled ones. This is a rare documentation of long-term effects after a major oil spill, highlighting the need for long-term monitoring in order to assess the real impact of this type of disturbance on marine organisms.
This is the annual update for OSPAR of the beached bird survey (BBS) results in The Netherlands (winter 2016/17), with a preview into 2017/18 (data that have thus far accumulated, up to and including to February 2018). The Dutch BBS provides data for OSPAR area's 8, 9 and 10, but data from Belgian and German colleagues will have to be merged to arrive at the final values for these areas. For the Dutch North Sea region, significant declines in oil rates were reported over a long study period (1977/78-2015/16) as well as (clearly accelerating) over the last 10-15 years, but the last seasons show consistently low oil rates in all species, including the target species Common Guillemot. In winter 2016/17, no major seabird wrecks have occurred, except an outbreak of avian flu affecting mostly Great Black-backed Gulls (Larus marinus) within the northernmost provinces of the country. The sample size for Common Guillemots was sufficient for the OSPAR subregions bordering the North Sea, but too small for the Wadden Sea region itself. The oil-rate (percentage of oiled Common Guillemots of all complete Common Guillemots found dead) reached an all-time low of only 3.0% (n= 166) for all studied areas, or 3.5% (n=141) for the North Sea coast of OSPAR areas 8 and 9 combined in 2015/16 (correction of the data provided in the previous report as a result of a larger sample size), but this value was slightly higher in 2016/17 (5.5% (n= 73) for all study areas combined, 6.0% (n= 67) for the OSPAR areas 8 and 9 combined). This current figure, however, is the second lowest value ever measured within The Netherlands and it follows and confirms the sharp drop in oil-rates that occurred after 2015. A preview into 2017/18 suggests that this extremely low level will be consolidated (5.0% oiled (n= 40) within the OSPAR areas 8 and 9 combined). The five-year running mean in (Dutch) national Common Guillemot oil rates (over 2012/13-2016/17; mean ± SD) arrived at 18.4 ± 16.2% (OSPAR 8-9) which is a further confirmation of a rapid decline. The results obtained over the last decade(s) suggest a continuation of low oil rates in Common Guillemots in Dutch waters. Following the significant trends in the most recent data set, a projection for 2020 is difficult to provide, because the recent decline in Common Guillemot oil rates accelerated and is no longer linear. The OSPAR target is clearly within reach.
This is the annual update for OSPAR of the beached bird survey (BBS) results in The Netherlands (winter 2015/16). The Dutch BBS provides data for OSPAR area's 8, 9 and 10, but data from Belgian and German colleagues will have to be merged to arrive at the final values for these areas. For the Dutch North Sea region, significant declines in oil rates were reported over a long study period (1977/78-2014/15) as well as (clearly accelerating) over the last 10-15 years, but the last seasons was unique in the series. In winter 2015/16, while the densities of pelagic seabirds washing ashore were not particularly low (hence, the sample size was excellent), the oil-rate (percentage of oiled Common Guillemots of all complete Common Guillemots found dead) reached an all-time low of only 3% (n= 165) for all studied areas, or 2.9% (n=140) for the North Sea coast of OSPAR areas 8 and 9 combined. The five-year running mean in (Dutch) national Common Guillemot oil rates (over 2011/12-2015/16; mean ± SD) arrived at 23.5 ± 15.7% (OSPAR 8-9). The results obtained over the last decade(s) suggest a continuation of low oil rates in Common Guillemots in Dutch waters. Following the significant trends in the most recent data set (2001/02-present), a projection for 2020 would arrive at c. 5%, meaning that the OSPAR target is within reach. A poorly treated oil-spill within the western Wadden Sea casted a shadow over this otherwise excellent beached bird survey result, but fortunately, few birds were affected.
Monitoring en vaststelling van het percentage met olie besmeurde Zeekoeten door middel van systematische strandtellingen in Nederland; jaarlijkse rapportage, winter 2015/16
Samenvatting
Dit is de jaarlijkse weergave voor OSPAR van de resultaten van systematische strandtellingen langs de Nederlandse kust, met een verslag over het seizoen 2015/16. Middels deze tellingen verzorgt Nederland haar bijdragen voor de OSPAR deelgebieden 8, 9, en 10. Om een compleet beeld te krijgen voor deze deelgebieden zullen Belgische en Duitse gegevens moeten worden toegevoegd en gecombineerd. In deze rapportage worden alleen de Nederlandse gegevens besproken. Voor de Nederlandse Noordzeekust kon de lange termijn afname in oliebevuilingspercentages (1977/78-2014/15) bij de Zeekoeten worden bevestigd. Over de laatste jaren versnelt deze afname. In de winter van 2015/16 spoelden behoorlijke aantallen zeevogels aan, waaronder ook Zeekoeten, en de monstergrootte is dan ook ruim voldoende om tot betrouwbare uitspraken te komen. Het (Nederlandse) nationale oliebevuilingspercentage van de Zeekoet bedroeg in de winter van 2015/16 slechts 3% (n= 165) indien berekend over alle gebieden en 2.9% (n=140) indien berekend over de Noordzeekust van OSPAR gebieden 8 and 9 gecomibineerd, hetgeen de laagste waarde is die ooit in Nederland werd gemeten sinds het olieslachtoffervraagstuk werd onderzocht (dat is sinds 1910). Het vijfjaarlijks lopend gemiddelde over 20011/12-2015/16 (gemiddeld ± SD) bedroeg 23.5 ± 15.7% (OSPAR 8-9). De oliebevuilingspercentages lijken de afgelopen jaren steeds sneller af te nemen. Op basis van de lineaire regressie berekend over de logit-oliebevuilingspercentages in deze eeuw (2001/02-2015/16) waarover een significante dalende trend werd gevonden, zou het bevuilingspercentage in 2020 uitkomen op ±5%, waarmee, aangenomen dat dit niveau zich over een periode van vijf seizoen handhaaft, één van de door OSPAR gestelde doelen wat betreft milieuvervuiling voor Nederland bereikt zou zijn. Het lage niveau en de voortzetting van de dalende trend wat betreft olievervuiling werd enigszins overschaduwd door een onprofessioneel afgehandeld olie-incident in de westelijke Waddenzee waarbij gelukkig weinig olieslachtoffers vielen. 4
Oil spills have been reported over several decades in many parts of the world including Nigeria. The region of Niger Delta is greatly affected by oil spills in recent years, Oporoma inclusive. About 635 persons (both females and males) from different groups e.g farmers, fisher men and women, community representatives, and youth leaders, were interviewed between the age of 18 and 90 years old. About 25 persons representing farmers and 25 persons representing fisher men and women from each of the twelve compounds that made up Oporoma community, 25 persons were randomly selected for community representatives, and 10 youth leaders were interviewed. The interview focused mainly on health and environmental impacts of crude oil spills in the community. The data and responses gotten from the interview shows negative health and environmental impact on crude oil spill in the community. The presence of crude oil and their constituents in the environment are capable of causing some acute and long-term adverse health effects. Some carcinogens like pyrene, benzene, and polycyclic aromatic hydrocarbons are always found in crude oil, which contaminates the surface water and soil. Therefore, affecting the environment through soil, water, and air, which directly or indirectly harms humans, plants and marine ecosystem. The influence of crude oil spills not only restricted to environment and human health, it has also had impacts on the nations and the local economy, which are includes; livelihoods, farmland, fishing, wild life, and the nations revenue.
Description
The first definitive exploration of the effects of this catastrophic oil spill since its occurrence in 1989. In addition to a comprehensive overview of the issues involved, 25 peer-reviewed papers cover the following key topics: • Chemistry and Fate of the Spill • Shoreline Impacts of the Spill • Effects on Fish and Fisheries • Effects on Wildlife • Archaeological Site Impact.
Description
The first definitive exploration of the effects of this catastrophic oil spill since its occurrence in 1989. In addition to a comprehensive overview of the issues involved, 25 peer-reviewed papers cover the following key topics: • Chemistry and Fate of the Spill • Shoreline Impacts of the Spill • Effects on Fish and Fisheries • Effects on Wildlife • Archaeological Site Impact.
Description
The first definitive exploration of the effects of this catastrophic oil spill since its occurrence in 1989. In addition to a comprehensive overview of the issues involved, 25 peer-reviewed papers cover the following key topics: • Chemistry and Fate of the Spill • Shoreline Impacts of the Spill • Effects on Fish and Fisheries • Effects on Wildlife • Archaeological Site Impact.
The sustainability of environment depends largely on the sustainable soil ecosystem as soil is taken as a key component of natural ecosystems. Soil contamination has been an environmental problem that is facing the whole regions of the world. The source of contamination may be either natural or anthropogenic. This research assessed the impact of oil spill on soil in Nigeria, using NNPC Depot as a case study. Soil samples were taken from the study area at four different points at a depth of 0.5-1.0 m using hand-dug auger. These samples were collected in sterilized bags and were well labelled. The following tests were conducted on the soil samples (contaminated and uncontaminated): Particle size distribution test, Compaction test, Atterberg Limit test and Permeability test. The particle size test revealed that the variation between the two samples (contaminated and uncontaminated) is insignificant but the presence of oil in the contaminated sample caused clod thereby making it difficult to pass through some sieve sizes. The Optimum Moisture Content (OMC) and the Maximum Dry Density (MDD) gave 11.40%, 1.98 g/cm³ and 9.50%, 1.81g/cm³ for both uncontaminated and contaminated samples respectively. Likewise, The Liquid Limits (LL) and plastic limit (Pl) gave 48 %, 33.5% and 33.6% and 14.9% for both uncontaminated and contaminated samples respectively. Also, the coefficient of permeability "k" gave 2.792 x 10-7 cm/s compared with the standard (soil permeability classes for Civil Engineering) falls within the impermeability limit (1 X 10-11-5 X 10-7) Thus the test results revealed that the contamination of soil by crude oil in NNPC Apata influenced the properties of the soil and subsequently leads to reduction in the values obtained for the entire test that the soil sample was subjected to.
Oil spills have killed thousands of birds during the last 100 years, but nonlethal effects of oil spills on birds remain poorly studied. We measured phenotype characters in 819 eiders Somateria mollissima (279 whole birds and 540 wings) of which 13.6% were oiled. We tested the hypotheses that (a) the morphology of eiders does not change due to oil contamination; (b) the anatomy of organs reflects the physiological reaction to contamination, for example, increase in metabolic demand, increase in food intake, and counteracting toxic effects of oil; (c) large locomotion apparatus that facilitates locomotion increases the risk of getting oiled; and (d) individual eiders with a higher production of secretions from the uropygial grand were more likely to have oil on their plumage. We tested whether 19 characters differed between oiled and nonoiled individuals, showing a consistent pattern. The final model retained seven predictor variables showing relationships between eiders contaminated with oil and food consumption, flight, and diving abilities. We tested whether these effects were due to differences in body condition, liver mass, empty gizzard mass, or other characters that could have been affected by impaired flight and diving ability. There was no evidence of such negative impact of oiling on eiders. We found that significant exposure to oil was associated with increased diversity of antibacterial defense. Oiled eiders did not constitute a random sample, and superior diving ability as reflected by large foot area was at a selective disadvantage during oil spills. Thus, specific characteristics predispose eiders to oiling, with an adaptation to swimming, diving, and flying being traded against the costs of oiling. In contrast, individuals with a high degree of physiological plasticity may experience an advantage because their uropygial secretions counteract the effects of oil contamination.
The human race has been involved in lot many activities on energy reservoirs, seeking the commercialization of agriculture and swift in industrial growth apart from mining activities, which has led to environmental pollution by many folds. There are a number of reasons for this environmental pollution; ingress of heavy metals into ecosystem, nuclear wastes as part of residue created due to nuclear energy power stations or atomic research activities, uncontrolled utilization of pesticides in our farmers, greenhouse gases and hydrocarbons generated due to various human activities are to name a few of them. If bioremediation activities are to be carried out successfully, they require a lot of time, but time and again have proved to be successful. In both ex situ and in situ ways, it is possible to carry out bioremediation.
The present century has seen tremendous progress in various types of renewable fuels and its possible applications. Fossil fuel, such as crude oil remained as prime source of energy, and it still fuels industries and households. In fact the demand for fossil fuels has increased in the last decade or so, because of increased population and demand due to industrial revolutions. It also leads to increased incidences of crude oil-related pollutions, oil spills, pipeline damages, accidental or intentional spillage, release from tankers, etc., which are quite persistent and very difficult to remediate. Heavy crude oil spillage is even more difficult to remediate, due to its hydrophobic, toxic constituents, and its partial or incomplete degradation leads to even more toxic intermediates in the affected environment. Harmful effects of crude oil spills are often observed in marine mammals, birds, and land-based animals, including humans. Commonly used remediation practices are often not quite effective and lead to only partial removal. Microbial biodegradation is reported to be an effective and environment-friendly alternative, which could be applied under both aerobic and anaerobic conditions onshore or offshore. Bacteria from marine and arid region are reported to be better biodegrader as compared to fungi. Several types of enzymes are reported to be quite effective for catalytic conversion of heavy crude oil and its derivative constituents. Recent progress in genetic engineering and omics techniques will be quite useful for further identifying the metabolomic routes and devising an efficient biodegradation to completely harmless end products.
Crude petroleum, refined petroleum products, and individual polycyclic aromatic hydrocarbons (PAHs) contained within petroleum are found throughout the world. Their presence has been detected in living and nonliving components of ecosystems. Petroleum can be an environmental hazard for all organisms. Individual PAHs can be toxic to organisms, but they are most commonly associated with illnesses in humans. Because petroleum is a major environmental source of these PAHs, petroleum and PAHs are jointly presented in this chapter. Composition, sources, environmental fate, and toxic effects on all organisms of aquatic and terrestrial environments are addressed.
The probability of major oil accidents in Arctic seas is increasing alongside with increasing maritime traffic. Hence, there is a growing need to understand the risks posed by oil spills to these unique and sensitive areas. So far these risks have mainly been acknowledged in terms of qualitative descriptions. We introduce a probabilistic framework, based on a general food web approach, to analyze ecological impacts of oil spills. We argue that the food web approach based on key functional groups is more appropriate for providing holistic view of the involved risks than assessments based on single species. We discuss the issues characteristic to the Arctic that need a special attention in risk assessment, and provide examples how to proceed towards quantitative risk estimates. The conceptual model presented in the paper helps to identify the most important risk factors and can be used as a template for more detailed risk assessments.
Hydrocarbon discharges into the ocean, both regulated and accidental, occur from offshore drilling and production operations, and can result in oil sheen (≤3 μm thick) and slick (>3 μm thick) formation, potentially harming marine birds. Sheens may commonly occur around offshore oil and gas platforms in Atlantic Canada, however, there is little information on regularity of occurrence. Further, there are few direct studies on potential impacts of sheens, associated with offshore oil and gas operations, on marine birds. We reviewed potential sources and frequency of hydrocarbon accumulation on sea surfaces from offshore oil and gas operations in Atlantic Canada, and the likelihood of overlap with marine birds. We conducted a literature review on lethal and sub-lethal effects of low levels of oil contact and ingestion on marine birds, focusing on studies that describe measured dosages of oil. We extrapolated from these data on low-dose oil exposure to link possible effects to marine birds resulting from exposure to sheens. We found that sheens occur around production operations in Atlantic Canada at allowable levels of oil concentrations in produced water. Frequency and extent of occurrence cannot be estimated from current monitoring practices. While immediate lethal effects to seabirds likely are not common from external oiling of feathers from sheens, added stressors, such as cold weather, can result in external oiling from sheens having significant impact on seabird metabolic rate and can be ultimately lethal. Ingestion of small amounts of oil, doses that realistically could be expected from exposure to sheens, in some cases resulted in sub-lethal effects to adult seabirds, primarily affecting metabolic rate, sub-lethal health impacts, and reproductive output. Nestlings and eggs do not come in direct contact with sheens, yet these life stages are highly sensitive to oil, and transfer of oil from adults exposed to sheens likely is above tolerance levels at times. Negative effects to reproductive output from small doses of ingested oil could be causing undetected impacts on marine birds and marine bird populations. Lack of standardized monitoring of marine bird contact with sheens and potential harm makes assessments of magnitude and extent of impact problematic.
The fertile waters of the North Sea form one of the major resorts for sea, shore and water birds of the world, and are also crossed by many migrating landbirds. A rough estimate of their numbers has been made by Evans (1973), who calculated that they may include over 2.5 million breeding seabirds in summer and over 2 million in the winter, with a little over 1.4 million migrant shorebirds or waders in the autumn and a little under 1.3 million in the winter, and a hundred thousand breeding wildfowl in summer, nearly half a million moulting birds in the autumn, and nearly three quarters of a million in the winter. The passing migrants may run into tens of millions. The total which is most easily checked, for breeding seabirds, subsequently proved to exceed four million (Bourne 1983a), and even this may also have been an underestimate. There are probably also a good many more sea duck, especially if one includes another population of a similar size frequenting the approaches to the Baltic (Atkinson-Willes 1975).
In one sense the term ‘environment’ represents all elements of the biosphere, but it is often of more use in the narrower sense of those parts or attributes of a habitat that are functionally significant during all or part of an organism’s life. All living organisms have a range of tolerance for each environmental factor, though the limits and the optimum may vary between individuals and populations as well as between species. They may vary according to life stage or reproductive condition and because of interaction with other environmental factors. It is to environmental factors that populations and species respond, either through evolutionary change or through phenotypic plasticity. The response persists (and the population or species succeeds) where this has led to continued, indeed often enhanced, efficiency in utilizing the environment.
Several authors of books on the monitoring of pollution have advocated the use of animals as monitors in terrestrial and aquatic environments (e.g. Phillips, 1980; Schubert, 1985). Such studies tend to emphasize the use of sedentary invertebrate animals as biomonitors. By comparison, birds suffer from several apparent drawbacks. They are mobile, so pollutants will be picked up from a wide, often ill-defined, area; they are long-lived, so pollutant burdens may be integrated in some complex way over time; and they have more complex physiology, and so may regulate pollutant levels better then invertebrates. Furthermore, birds tend to be more difficult to sample, and killing birds may be unacceptable for conservation or ethical reasons. However, some of these characteristics may at times be positively advantegeous. Integrating pollutant levels over greater areas or timescales or over food webs, may be useful, provided that species are chosen carefully. Less sampling may be necessary if birds can reflect pollutant levels in the whole ecosystem or over a broad area. In addition, since they are high in food chains, birds may reflect pollutant hazards to humans better than do most invertebrates. It is also significant that birds are extremely popular animals with the general public, so pollutant hazards to them are likely to receive greater attention than threats to invertebrates.
This is the annual update for OSPAR of the beached bird survey (BBS) results in The Netherlands (winter 2014/15). The Dutch BBS provides data for OSPAR area’s 8, 9 and 10, but data from Belgian and German colleagues will have to be merged to arrive at the final values for these areas. For the Dutch North Sea region, significant declines in oil rates were reported over a long study period (1977/78-2013/14) as well as (clearly accelerating) over the last 10-15 years. In winter 2014/15, densities of pelagic seabirds washing ashore were again very low. Some oil incidents (mystery spills, no source known, deduced from stranded seabirds) were recorded in Zeeland, affecting mostly Common Guillemots, but numbers stranded remained low.
The (Dutch) national oil rate of Common Guillemots in winter 2014/15 amounted to 32.4% (n= 37), with the five-year running mean over 20010/11-2014/15 (mean ± SD) at 30.2 ± 11.6%. For five other selected offshore species, not a single oiled carcass was reported, but the sample size was too small for a meaningful assessment of the annual oil rate. The results obtained over the last decade suggest an continuation of low oil rates in Common Guillemots in Dutch waters. Following the significant trends in the most recent data set (1999/00-present), a projection for 2020 would arrive at c. 19% (logit -0.64).
In 1913, J. H. Gurney published The Gannet, a Bird with a History, which enumerated all known gannetries and their populations. It is no accident that a seabird was chosen for this first attempt to estimate the world population of an avian species, because seabirds are often large and conspicuous and breed in imposing colonies that invite census. The colonial habit of seabirds also encourages studies of breeding and demography, as large amounts of data can be gathered without need to search for widely dispersed nests. David Lack, doubtlessly inspired by early seabird exposure in Iceland and Bear Island, used marine birds prominently in developing the hypothesis that breeding systems evolve to maximize reproductive output (Lack, 1954, 1966, 1967). Seabirds were also presented as champions of the opposing view, now in disfavor, that animals may limit reproduction for the benefit of the species (Wynne-Edwards, 1962).
Oil may be a variety of materials, including crude oil, refined petroleum products or by-products, oily refuse or oil mixed in waste. With a high content of several organic compounds, oil may be the target of several terrorist attacks or may be spilt by accident. The term "oil spill" mainly refers to marine oil spills, where oil is released into the ocean or coastal waters. Oil spills must be taken into consideration seriously as sea organisms can either be poisoned by ingestion or can be affected by direct contact. On the other hand, oil well fires are oil gushers that have caught on fire and burn uncontrollably. These fires are more difficult to extinguish than regular fires due to the enormous fuel supply for the fire. Exposure to their dust and smoke can cause several short-term and longterm health effects as there comprise of several compounds like gases, acidic gases, polycyclic aromatic hydrocarbons, metals, volatile organic compounds and particulate matter. This review will mainly focus on oil spills, oil well fires and their environmental and health effects. Besides, measures to be taken are also covered by this contribution.
In this paper-conducting polymer gas sensor based AutoNose electronic nose (E-Nose) technology has been used for detection of oil contamination in seawater samples. AutoNose E-nose is a headspace analyzer based on six conducting polymer sensors. Seawater samples with known (or induced) oil contamination were tested and classified against the unpolluted seawater samples using machine learning based ensemble classifiers with very high accuracy. We show that a simple headspace sensing E-Nose could be used to rapidly detect oil pollution in seawater for early biosecurity prevention.
(1) The number of recruits to the North Shields kittiwake colony in N.E. England (Coulson & Thomas 1985) increased from 1954 to 1967, but the proportion of first breeders decreased during that time. Increased mortality of the breeding birds or the provision of more sites increased recruitment. This implied that there was a pool of potential recruits from which the new recruits needed could be drawn. In most years there appeared to be a non-breeding reservoir. (2) About 11% of each cohort returned to breed in their natal colony. Immatures did not suffer the same variations in mortality as did adults; this finding is consistent with the premise of Coulson & Thomas (1985) that increased adult mortality associated with the decline in numbers in the late 1960s occurred prior to the breeding season. (3) The age of first breeding fell from 5 to 4 years in response to high adult mortality in the early 1970s; body weights and wing-lengths of male and female recruits diminished, but the body weights of male and female prospectors fluctuated little. (4) A model of colony growth is presented, based on the relationship between colony size and rate of increase in expanding colonies of British kittiwakes. Small colonies grow faster than large ones, and are proportionately more attractive to recruits. Small colonies cannot produce enough young during the first 70 years and are sustained by immigration. (5) The North Shields colony is not a closed system and is not currently growing; it is supported by immigration. There is a positive relationship between colony size and nesting density; colony growth appeared to be limited by the number of attractive sites in the dense centre of the colony. There were sites available on the periphery which were not used. The importance to breeding of the buffering effect of the pool of potential recruits is discussed.
Recoveries of ringed guillemots Uria aalge and razorbills Alca torda were used to investigate the effects of the severe oil pollution over much of NW Europe in winter 1980-81 on British and Irish auk populations. Except for the Skagerrak incident, most deaths were caused by chronic pollution from unidentified sources. Comparison with the ringing results from the winters 1967-68 to 1978-79 showed a significantly higher percentage of recoveries reported as oiled for first year guillemots and adult razorbills. First year guillemots, immature guillemots and adult razorbills experienced increased mortality in the winter of 1980-81. Regional differences in recovery rates of first year and immature guillemots showed that Orkney, Shetland and East Coast populations were most severely affected. Guillemot breeding populations may decline on average by 6-9% over a 5 yr period, mostly in 1985 when the majority of the 1980 cohort would normally be recruited to the population. Razorbills may experience an immediate decline of 3-6%.-from Authors
Sixteen incidents of oil pollution involving >50 birds occurred around the British Isles between July 1978 and June 1979, with the highest number and greatest impact in the Orkney and Shetland areas. The winter counts of the Beached Birds Survey provide data from >2000 km of coast. -P.J.Jarvis
Because eggs of marine birds may be exposed to oil adhering to the feathers of adult birds, a study was undertaken to determine the effects of oil contamination. Two hundred common eider eggs (Somateria mollissima) were divided into four experimental sets of 50 each. Two sets were treated with No. 2 fuel oil in amounts of 5 μ1 and 20 μ1; a third with 20 μ1 of propylene glycol, a neutral blocking agent. The fourth set served as a control. Hatching success was 96 percent for the eggs treated with 20 μ1 propylene glycol, 96 percent for the controls, and 92 percent for the eggs treated with 5 μ1 oil hatched. Only 69 percent of the eggs treated with 20 μ1 of oil survived: a significant reduction in hatchability (P⋜0.05). Mean hatching weights for all sets were statistically equal. Thus, oil pollution may significantly increase embryonic mortality in marine birds.
Seabirds are marine animals. A great deal is known about their ecology, yet paradoxically almost all this information has been collected at the birds’ breeding sites on land (see, e.g., Bédard, 1969; Belopol’skii, 1961; Cramp et al., 1974; Fisher, 1952; Fisher and Lockley, 1954; Nelson, 1970; Nettleship, 1972; Richdale, 1963; Salomonsen, 1955; L. M. Tuck, 1961). Yet remarkably little is known about the 50% or more of their lives that seabirds spend at sea. This is partly because of the technical difficulties in studying seabirds at sea. But it is unfortunate, too, that the pelagic aspects of seabird ecology fall between the disciplines of ornithology and oceanography, and neither side has been very eager to bridge the gap. Ornithologists tend to think of the sea as something flat, wet, and relatively uniform, over which their birds happen to fly. Oceanographers and marine biologists know that it is far from uniform, but seem reluctant to concede that these airborne, highly mobile animals, which cannot even breed at sea, could ever be associated with specific and relatively localized marine habitats or species communities.
Apparent abundance, measured by catch-per-effort in the commercial fishery, of the anchoveta, Engraulis ringens, in the Peru Current, during 1966, 1967 and 1968 has been above that expected from earlier analysis of the relation of apparent abundance to commercial fishing effort. During these years there has also been apparent enhanced recruitment, measured by the catch-per-effort of the entering year-class. During these same years, however, the guano birds, that also feed on E. ringens, have been at a low population level compared to previous years. Combining the fishermen's catch with the harvest by guano birds, for fishing years 1960–61 through 1967–68, relating this to the total fishing effort by the two predators, and treating this as a single fishery, it is shown that the combined data are well fitted by the logistic model for the catch-effort relationship. The maximum sustainable yield of the combined fishery is about 10 million metric tons per year, presently shared, approximately, 9.3 mil...
The results of a study of the feeding biology of nine sea-bird species breeding on the Farne Islands Northumberland, showed that: 1. Fish is the predominant food of all the species studied. 2. There is a considerable overlap between the size and species of fish taken by each of the sea-bird species. 3. The food obtained by each species is not necessarily taken from the same area, each species showing differences in the average distance travelled in search of food and the depth at which food is obtained. 4. The three species of terns which were studied were close to the limits of their physical ability to collect food whereas the larger sea-birds had considerable reserve of time which could be utilized for fishing should fish be less abundant. 5. During 1961 and 1962 there was little evidence to suggest that large broods were reared less successfully than those with only one chick. 6. Chicks on the Farne Islands grew more rapidly than did chicks of the same species in the Arctic, implying that available food was at least as abundant in this area as in the Arctic during the richly productive summer months. These results suggest that during the study there was a superabundance of food and there was little or no starvation of the young; if food should at any time be less abundant, then it is possible that the different feeding areas may well limit any interspecific competition. No evidence was found of competition for any resource occurring between any of the congeneric species breeding on the island, even when there was no apparent ecological division between species. It is concluded that in the fish-eating species of sea-birds breeding in the study area, brood size is not limited by food supply.
(1) In 1972, the then Nature Conservancy undertook to control the number of breeding herring gulls Larus argentatus Pont. on the Isle of May (Scotland). Culling has since continued. (2) Prior to this, herring gulls were increasing at 13% p.a. with an annual recruitment rate of 17.3%. The breeding population was estimated in 1972 at 16 700 pairs. By 1977 the population had been reduced to 3670 pairs. The number of recruits also dropped in each year well below predicted levels. (3) Over 38 000 gulls were killed between 1972 and 1976, but it seems that large numbers of recruits have been deterred from breeding as well. These are presumably breeding elsewhere. (4) The average age of recruitment was 5.0 years. The age composition (which was stable from year to year before 1972) has been greatly changed, with 52% of the population breeding for the first time in 1977. Few old birds have been left. (5) Nest density is important in regulating recruitment rate. Areas of the colony which were most attractive to new recruits had between two and ten pairs of gulls per 100 m. At higher densities the number of new recruits was sufficient to balance natural annual adult mortality. No recruits were attracted to areas with a density less than two pairs per 100 m. (6) The gull cull has lowered the pre-1972 average breeding density (estimated at 11.1 pairs per 100 m) to 2.3 pairs per 100 m. (7) In the event of culling being stopped, it is possible that the existing density retains sufficient attraction for a high recruitment rate to be maintained, with a consequent increase in the breeding population.
A number of population parameters for the Common Guillemot are presented, derived from a study of marked birds on Skomer Island, Wales, and from recoveries of ringed birds. Breeding success on Skomer averaged 0.7 chicks/pair, and in two years adult survival averaged 91.5%. Guillemots returned to Skomer in their second year, and prior to breeding birds congregated in clubs. Guillemots first bred at four years old, but most of them probably breed for the first time in their fifth year. Two different estimates for the survival rate of birds up to five years old were: 16% and 20%. Juvenile survival calculated from ringing recoveries varied from 27% for southern England, where numbers are stable or decreasing, to 41% in north-east Canada, where numbers have increased. Between 1972 and 1977 the Skomer Guillemot population remained at a similar level. If adult survival is 91.5% and 100 pairs of Guillemots produce 70 chicks, 17 (24%) of these must survive to breeding age to maintain a stable population. Factors influencing population size are discussed.
Measurements of the rates of population increase, reproduction, and mortality together with an observed age ratio, were used to analyze the population of the Herring Gull in New England. Data from sporadic censuses prior to this study, aerial censuses by the authors, and National Audubon Society Christmas Bird Count indicated that the New England breeding population has been doubling every 12 to 15 years since the early 1900's. This increase has involved founding new colonies and expanding the breeding range There is evidence that 15 to 30% of the adults do not breed in any given year. Sixty-one productivity measurements on 43 islands from 1963 through 1966, involving almost 13,000 nests, showed that from 0.8 to 1.4 young/breeding pair/year is the usual range of rate of production. The age distribution in the population was determined by classifying Herring Gulls by plumage category on an aerial census of the coast from Tampico, Mexico, to Cape Sable, Nova Scotia. Of the 622,000 gulls observed, 68% were adults, 17% were second- and third-year birds, and 15% were first-year birds. Mortality rates derived from band recovery data were too high to be consistent with the observed rate of population growth, productivity, and age structure. Loss of bands increasing to the rate of about 20%/year 5 years after banding eliminates most of the discrepancy. The age structure and rate of population increase indicate a mortality rate of 4 to 9% for gulls 2 years old or older, compared with the 25 to 30% indicated by band recoveries. The population structure we have developed fits everything we have observed about Herring Gull population dynamics, except mortality based on band recoveries.
(1) This paper reports on a 5-year project set up in Mainland, Orkney, Scotland to assess annual and longer-term changes in numbers of four seabird species against a pattern of temporal variability. (2) Between five and ten standardized counts of individuals guillemots Uria aalge, razorbills Alca torda, kittiwakes Rissa tridactyla and fulmars Fulmarus glacialis and apparently occupied nests and sites of kittiwakes and fulmars were made in fixed plots at five colonies in the month of June from 1976 to 1980. (3) Analyses of variance were used to test for changes in numbers between years. The method's sensitivity using five or ten counts per year was assessed by calculating the power of the two-tailed t-test for specified proportionate changes in the mean counts. (4) Between 1976 and 1980 there were significant differences between annual colony means in all the species and categories counted. Interaction of colonies with years for all categories (except kittiwake nests) indicated unidirectional change but at different rates. For kittiwake nests, interaction indicated opposing trends in the colonies. All colonies showed mean annual increases in numbers of individual guillemots, razorbills and fulmars and fulmar sites (except Costa Head). There were mean annual decreases at all colonies (except Mull Head) in numbers of kittiwake nests and individuals. (5) Five counts per year were sufficient to detect proportionate changes of +-30% for guillemots and kittiwakes (nests and individuals) and fulmar (individuals). To achieve this precision for razorbills, ten counts would need to be made in a shortened sampling period. Fulmar sites were borderline, probably partly because of the subjectivity involved in defining this category.
(1) Methods used to estimate energy requirements of avian communities are listed, and their inadequacies discussed. In particular, the published estimates lack confidence intervals. (2) A simulation model is described which estimates daily energy requirements of seabird populations. Biomasses of breeders, non-breeders and chicks present in the vicinity of the colony, are coupled with an ambient temperature function, the bioenergetic equations of Kendeigh, and calculations of the energy costs of digestion, activity, egg production and growth. (3) The model is tested using input data sets for great skua Catharacta skua Brunnich and Arctic tern Sterna paradisaea Pontopp. Sensitivity of the model to errors in input parameters, and the output errors resulting from known imprecisions in the forty-four input parameters are examined. Output precision is largely determined by a few parameters, which depend partly on the life-style energy allocation of the species. (4) A Monte Carlo simulation is used to determine the precision of the estimated energy requirements of the two species' populations. This suggests that, using currently available input data, the population energy requirement estimate has a 95% confidence interval of +-50% of the mean. (5) Energy requirements could be considerably more precisely determined if only a small number of input parameters were more precisely known. These limiting parameters are listed. (6) The model is applied to one particular seabird community, on Foula, Shetland, for which detailed data have been collected. The mean estimate of the total energy requirement of this community (1.2 X 1010 kcal yr-1) represents 29% of the mean estimate of the total annual fish production within a 45 km radius of the colony. This implies that seabirds, predatory demersal fish and industrial fisheries are in direct competition for the energy flow from pelagic fish, such that any increase in the energy flow to one of these would result in a reduced energy availability to the others.
(1) Previous extensive ringing and the cull of herring gulls between 1972 and 1974 on the Isle of May by the Nature Conservancy Council facilitated an investigation of recruitment of this gull species. (2) The colony of herring gulls on the Isle of May has been increasing at about 12% per annum for most of this century, and there is little evidence of large and irregular increases in numbers. Since 1950, the mean rate of increase has been 13% per annum. This rate of increase is similar to other herring gull colonies elsewhere in Britain. (3) Using the survival of gulls ringed as adults prior to the cull, the average annual survival rate is estimated as 0.935+-0.10 whilst the survival rate in the first year of life was calculated as 0.83, 0.83 and 0.67 in three successive year classes. (4) The Isle of May is a dense colony and no three-year-old birds were found holding territories or breeding. Some four-year-old gulls held territories and bred but the proportion was low and varied between years. It is estimated that the mean age of first breeding is 5.25 years with 55% of the birds breeding for the first time when five years old. Some individuals probably do not breed until seven years old. (5) There was no evidence of differences in the age at recruitment of male and female herring gulls. (6) Calculations based on the life-table of the herring gull and the number of marked recruits recovered during the cull lead to the conclusion that about 65% of the surviving young did not return to the Isle of May (their natal colony) to breed. Young reared on the Isle of May have been found nesting up to 250 km away. (7) Of those recruits which returned to nest on the Isle of May, 65% nested close to their place of birth. (8) Males showed a stronger tendency to return to their natal area than females, and this was evident both amongst those birds nesting on the island and through a higher proportion of females emigrating into other colonies. (9) Preliminary experiments suggested that recruitment is influenced by the density of breeding birds. Recruits were attracted to dense areas but they had much greater difficulty in establishing a territory there. (10) A simple model of the recruitment process has been presented which should act as a basis for further research. (11) The material presented in this paper has considerable implications for the management of gull colonies. The considerable emigration of young reared in the colony and the consequent immigration from other areas suggests that the reduction of gull colonies on a local scale may well result in massive immigration. Control programmes should endeavour to clear areas completely and, if some gulls are to be retained, then these should be encouraged to nest at high densities.
(1) In twenty-seven fulmars breeding for the first time, breeding success tends to be higher in those that are at least as old as the mean age at first breeding (9.2 years, S.E. =0.39), due to improved fledging success. (2) Breeding success shows a significant positive correlation with age in fulmars with not more than three years breeding experience. (3) Breeding success shows a significant positive correlation with length of breeding experience in birds from 6 to 11 years old, but not from 12 to 19 years old. (4) Breeding success shows a significantly different relation to breeding experience of the male than to that of the female. Males show a significant positive correlation between breeding success and breeding experience from their second to twenty-first breeding year; females show a significant positive correlation from their second to seventeenth breeding year, with a tendency for success to decline thereafter. (5) Significantly more males than expected pair with females with less breeding experience than themselves. (6) Breeding success shows a significant positive correlation with duration of pair-bond, if it assumed that the pair-bond persists during years in which one member of the pair was not identified. (7) The mate and site of the previous year are retained in about 90% of cases. Changes tend to result in lower breeding success, especially in females. (8) There are indications from new pairs with at least one experienced bird that the male may influence the choice of nest site more than the female, and this results in better breeding success. (9) Change of mate occurs at 5% per annum, mostly due to disappearance of the mate. When divorce is followed immediately by re-pairing, breeding success before the divorce tends to be poorer than that of the newly formed pair. (10) Change of site occurs at 6-7% per annum. Pairs which change their site tend to have higher breeding success at the new site than they did at the old one. (11) There are indications that capture, especially of birds recorded breeding for the first time, reduces their success in the year of capture, and reduces the proportion of these birds seen breeding in the following year. (12) Breeding success shows a significant negative correlation with laying date. Established pairs laying after the median laying date are significantly more successful than new pairs which do so, but there is no significant difference before this date. (13) Laying date does not correlate significantly with breeding experience though the mean laying date of newly formed pairs is significantly later by 1-2 days than that of established pairs, and the mean laying date of pairs with an inexperienced male is significantly later by 1-2 days than that of pairs with an experienced male.
Colour-ringed Fulmars caught as breeders were observed during their attendance at the colony between October and May. Their breeding performance was determined for comparison with winter behaviour. The first birds arrived on land in late October. Thereafter, numbers varied erratically, high numbers being associated with low wind speeds. Overall, neither sex preceded the other to land, but males were always more numerous than females and attended more frequently. Nest-sites were defended throughout the winter by their owners, but there was no evidence of strong intraspecific competition for sites. Fulmars always won in competition with Herring Gulls. Individuals did not range far from their nest-sites when on land. Most associations involved mated pairs. Many of the birds present in winter (between 18% and 50% of the total population) were not local breeders. No significant relationships were revealed between winter behaviour of marked individuals and their previous or subsequent breeding performance.
The numbers of Guillemots on selected cliff ledges of the island of Copinsay, Scotland, were counted four times a day both before egg-laying and at around the time of hatching. Counts of arrivals and departures and behavioural observations were also made at a small study colony. Early season counts showed great variation, the major factors responsible being the time of day, the state of the tide, wind speed and disturbance by gulls. Numbers were more constant later in the season, although they still varied with time of day and there was also some evidence that wind speed and precipitation affected them. There was an upward trend in numbers during this time; behavioural observations suggested that this was due to greater attendance by birds with chicks.
(1) Data have been accumulated over a period of twenty-one years on the survival of the breeding kittiwake gulls in a single colony. (2) Analysis of the data shows a consistently higher annual survival rate among females (0.86 in females, 0.81 in males). The difference between the sexes increases in years when the total survival rate is low. (3) The survival of adult kittiwakes decreases progressively with their age, and is highest in both sexes in the year following first-breeding. This decrease in survival rate with age agrees closely with the suggestion of Botkin & Miller (1974) that age-constant survival, which previously has been regarded as typical of adult birds, is unlikely to occur in long-lived species. (4) During the growth phase of the colony, the survival rate of males in the centre of the colony was significantly higher than those at the edge, but in the more stable phase this effect has virtually disappeared, coinciding with an overall decrease in the survival rates of both sexes. (5) The survival rate of kittiwakes in the colony has tended to decrease over the twenty-one years of this study and this trend persisted even when birds of the same age were considered. The decrease in survival rate in recent years is not likely to be caused by toxic chemicals, since the levels of these tend to be low in this species. The lower survival rate is probably associated with the increased density and competition in the `maturing' colony, which has also resulted in a much earlier annual reoccupation of the colony. (6) Most of the mortality in both sexes occurs during the late autumn and winter when the birds are oceanic and not near their breeding colony. There is an indication that the higher mortality of males relative to females occurs particularly during January to March, at which time the male is active in defending its nest-site and obtaining a mate.
(1) Contemporary factors which could affect the probability of identifying breeding birds (and therefore affect estimates of survival rate) are examined. The following are found to have significant effects: stage of breeding cycle and breeding season at which observations are made; failure of nest; capture of either bird. (2) Previously experienced factors which could affect the probability of identifying breeding birds are examined. The following have significant effects: length of previous breeding experience of either bird; capture in the previous year, in particular the first capture of females; failure in the previous year. (3) It is concluded that there are more factors reducing the probability of identification of females than of males, but in practice these factors will be negligibly small. (4) The latest estimate of mean annual survival rate for adult breeding fulmars (Fulmarus glacialis L.) is 0.9710 for males and 0.9722 for females, with breeding adult life-expectancies of 33.92 and 35.47 years respectively, using the Maximum Likelihood method, and data from 1958-74. (5) There is evidence of a decline in survival rate with age, though breeding success is positively correlated with age.
Synopsis
The programme for ornithological monitoring in Shetland has concentrated on selected species of cliffnesting seabirds and inshore waterfowl. Sample study sites throughout Shetland have been selected and standard counting methods derived. These have taken account of factors such as logistics and accessibility, the effects of weather and observer error and of the seasonal and diurnal variations in the numbers of birds.
Changes in seabird and waterfowl numbers between 1975–79 have been observed. These, with the exception of the bird mortality following the Esso Bernicia oil spill, have been attributed to natural variation. From the scale and local differences between these as yet short-term observations, estimates are presented of the minimum percentage change required in either numbers of birds or their nests before such natural variation is exceeded.
The problems of interpreting changes in numbers are discussed.
The number of dead birds picked up in Sullom Voe after the Esso Bernicia spill corresponded closely to that estimated from the monitoring counts before and after the incident.
The Fulmar has a long period at the breeding colony prior to egg-laying. The pattern of annual occupation and build-up in numbers has been examined in detail at Marsden, Co. Durham, at a colony in which over 100 eggs are laid annually (Order 3 of Fisher's classification).
The re-occupation of the cliff starts in early November with an occasional visit by one or two birds. The main period of activity at the cliff is during the morning and, as the numbers build up, the diurnal period of occupation increases. By mid-December the first birds to arrive in the colony do so before dawn and the last to leave remain well after dark until near midnight. Almost throughout the pre-egg stage, the colony is deserted each night and re-occupied the next day and birds only stay regularly overnight just before egg-laying. A similar pattern of occupation occurs after breeding but in the reverse order.
The numbers of birds at the colony in January and February exceed the breeding population and include many non-breeders. The non-breeders progressively decline in numbers until May when only the breeding birds remain with a few non-breeding birds.
The daily variation in the numbers of birds at the cliff is influenced by the wind speed. In general, the birds leave the colony under freshening conditions and the number present at the colony can be interpreted in terms of the wind conditions over the last three days.
It is suggested that the synchronised departures are primarily feeding trips, the birds using the strong winds to reach feeding areas, except that the departure just before egg-laying is linked to egg development and synchronised laying in the colony.
Competition between Fulmars and Kittiwakes for nesting sites usually results in the Kittiwakes gaining the site. This is achieved by the Kittiwakes taking over the Fulmar sites during one of the latter's departures.
Ringing recovery data from British Razorbills are used to obtain information on the birds' movements outside the breeding season and it is shown that great care needs to be exercised in the interpretation of such data. Comparisons are made with the previous analyses of Razorbill movements.
It is well known that Fulmars from British colonies penetrate north to the Barents Sea and west to Newfoundland and Greenland. This paper investigates the marine range in relation to the age of the birds.
The jackass penguin Spheniscus demersus (L.) is confined to the coastal waters of southern Africa, and breeds on 18 islands predominantly within the region of the cold, nutrient rich Benguella current. Since the early 1900s the species' population has declined in numbers of unknown magnitude. The decline appears to be continuing, although the absence of reliable census data precludes an accurate measurement of the rate of change. The initial fall in numbers was undoubtedly due to severe disturbance of nesting birds and excessive commercial exploitation of eggs. The average annual egg crop for the period 1900-30 exceeded 450,000 eggs from Dassen Island alone. Egg collection has been suspended temporarily, but the species now appears to be threatened by oil pollution, and by competition with a pelagic shoal fish industry. Threats to breeding colonies are posed by harbour developments. These factors are discussed and evaluated. South African marine organisms are considered officially to be an economic resource and are heavily exploited. Legislation governing the control of this resource is the concern of the Ministry for Economic Affairs. There is no provision for any government body to investigate the status and biology of economically insignificant, but yet integral, components of the marine ecosystem. The major priority of conservations is to safeguard the jackass penguin population at its present level. This includes proclamation of several offshore islands and their surroundings as national nature reserves. We consider current efforts to rescue, clean and rehabilitate oiled seabirds as contributing little to conservation in real terms, even though the activity has an important humanitarian and educational function. Research priorities include a comprehensive census of the jackass penguin and other seabird populations in southern Africa; a study of mortality and recruitment, with particular attention to factors affecting the rates of these processes; a study of the dynamics of the penguin/prey interaction, with special reference to the possible effects of competition with the pelagic fishing industry; an evaluation of the degree of disturbance that nesting penguins can tolerate; an investigation into the temporal and spatial patterns of oil pollution incidents, oil slick occurrence and movement, and the development of methods of keeping birds away from oil slicks; and, lastly, an evaluation of the efficacy of rehabilitating oiled penguins as a contribution to maintaining or increasing the current jackass penguin population. The responsibility for these projects rests with the South African government.
Puffins Fratercula arctica were studied on Skomer Island, Wales (51°44′N, 5°19′W) during 1972-77. Annual survival of breeding adults was 95%. Each year, 20-27% adults were without nesting burrows, and 2% were absent from the colony. 64% of pairs with burrows fledged a chick, with 5-16% not laying, 22-25% eggs not hatching, and 5% chick mortality. Much of the egg loss was caused by disturbance from prospecting Manx Shearwaters Puffinus puffinus which competed with Puffins for burrows. Data on the feeding and growth of chicks is given. Young Puffina first returned to the colony at two, or more usually three, years old. Four years was the earliest age for first breeding. At least 10-16% fledglings survived to four years old; it was not clear whether enough survived to replace adult mortality.
Breeding populations of Anas platyrhynchos, A. strepera, A. crecca, A. penelope, Aythya marila, A. fuligula, Bucephala islandica, Clangula hyemalis, Melanitta nigra, and Mergus serrator were studied at Lake Mývatn in northeast Iceland (65°35′N, 17°00′W) during 1960 through 1970. Reproductive success and fluctuations in the size of the populations were studied in relation to the available resources. The variations and effects of certain breeding parameters, such as breeding frequency, hatching success, and duckling mortality, determining the reproductive success (full-grown young per female) were investigated. Relative scarcity of chironomid larvae (chief food item of the diving ducks and young) in 1970 was associated with reduced breeding frequency and a high rate of nest desertion (low hatching success). The survival of ducklings was mainly determined by the prevailing weather conditions during the week following hatching; therefore the total number of full-grown young was not closely correlated with the size of the breeding population. The reproductive success did not have an appreciable effect on the size of the population in subsequent years. /// Исследовали динамику популяций Anas platyrhynchos, A. strepera, A. crecca, A. penelope, Aythya marila, A. fuligula, Bucephala islandica, Clangula hyemalis, Melanitta nigra и Mergus serrator на озере Миватн в северовосточной Исландии (65°35′с.ш. и 17°00′в.д.) с 1960по 1970гг. Изучение интенсивности размножения и колебаний численности провдили с учетом количества доступной пищи. Исследовали изменения определенных параметров размножения - перодичности размножения, процента вылупления и смертности птенцов; определяли количество выросших птенцов от одной самки. Относительно низкая численность личинок Chironomidae (основная пища птенцов и молодых птиц) в 1970г. коррелировала со снижением частоты размножения и высокой скоростью оставления гнезд (низкий процент вылупления). Развитие птенцов определяется в значительной степени погодными условиями в течение недели, следующей за вылуплением. Таким образом, общее количество выросших птенцов не коррелирует с размерами популяции. Размножение не оказывает существенного влияния на размеры популяции в последующие годы.
The greatly increased use of helicopters and fixed-wing aircraft to support the exploration and exploitation of oilfields in the North Sea gives rise to concern about possible disturbance to seabirds breeding in the flight paths. The observations reported in this paper were made at a mixed colony of fulmars (Fulmarus glacialis), shags (Phalacrocorax aristotelis), herring gulls (Larus argentatus), kittiwakes (Rissa tridactyla), guillemots (Uria aalge), razorbills (Alca torda), and puffins (Fratercula arctica), breeding on the Buchan cliffs about 40 km north of Aberdeen, on two days during egg-laying and early nestling stages of the breeding season.The number of birds in attendance at nests or nesting ledges were counted before and after the passage of aircraft, and general observations were made when the planes were overhead. The number of identifiable nests with 0, 1 or 2 adults was noted since disturbance might be most sensitively detected by the departure of non-incubating/brooding adults.No evidence was found to suggest that aircraft flying at heights of about 100 m above the cliff-top affected the attendance of incubating and brooding birds, and there was only a slight indication that a few of the ‘second adults’ at kittiwake nests may have flown off. Groups of kittiwakes resting on nearby cliffs or on the sea did take to the air in response to the planes, but they also did so frequently in the course of the day with no obvious cause. It is stressed that these findings cannot be extrapolated to other species of seabirds or to different conditions.
Breeding of the Cape cormorant on the South West African platforms and of the jackass penguin on islands off South Africa is coincidental with the seasonal availability of pelagic fish shoals. The largest numbers of Cape gannets and Cape cormorants occur off South West Africa where the biomass of fish is highest, though dominated by one species, the pilchard. By contrast, jackass penguins, limited in their range through flightlessness, are concentrated at the centre of the smaller but more stable South African multispecies fishery. In both South West and South Africa, densities of Cape cormorants are heaviest near the recruitment grounds for juvenile pilchard and anchovy. Island yields of guano are shown to provide reliable estimates of bird population sizes and fluctuations in these are closely related to temporal changes in fish abundance. They consequently have value in providing an understanding of fish stocks prior to exploitation and as indicators of the current state of the resources. Since the turn of the century large oscillations in the South West and South African pilchard populations were apparent but overfishing in the 1960s depressed both below their normal levels and reduced the numbers of birds.
Sublethal doses of petroleum reduced reproduction in a free-living seabird, Cassin's Auklet (Ptychoramphus aleuticus), nesting on Southeast Farallon Island, California. The proportion of birds laying eggs was reduced 9–13 days after ingestion by gelatin capsule of 300, 600 or 1000 mg bunker C fuel oil, or 1000 mg Prudhoe Bay crude oil. In addition, among those auklets that eventually laid eggs, hatching was reduced by doses of 1000 mg of bunker C but was unaffected by other treatments. Chick development after hatching was unaffected by any treatment. The total time of egg formation from onset of rapid yolk formation to laying was 13 days, and it is early in this period that auklets are vulnerable to petroleum.
Oiled birds appear to be a commoner aspect of oil pollution where it occurs with cold water-temperatures, whereas the formation of tar-balls becomes more prominent with warm ones, possibly because liquid oil becomes reduced to inert solid residues comparatively harmless to birds more rapidly at higher temperatures.