Refuse Tips Research Articles

Marginal presence of plastic in nests of yellow–legged gulls (Larus michahellis) in the southeastern Bay of Biscay

Nest entanglement and consumption of plastics can be a cause of mortality in chicks of various seabird species. As plastic debris may be chosen as a source of nesting material, evaluation of its presence and contribution to nest building in seabird colonies is important. Here, we determined the contribution of anthropogenic debris to nest construction by a yellow–legged gull Larus michahellis population that largely depends on refuse tips to forage. Two colonies within the southeastern Bay of Biscay, Spain, were sampled in 2019. One of the colonies was in Getaria, where no debris was found in nests, and the second was in Ulia, where 40 % of the nests had some kind of artificial material. In all cases, however, this debris comprised less than 5 % of the nests’ area. Among the studied nests, we found one had a piece of fabric, five had pieces of rope, and 20 had pieces of flexible plastic packaging. These results contrast with other seabird species that face problems of conservation due to the increasing use of plastic for nesting. With the low prevalence of artificial debris (chiefly plastic) in nests found in this study, mortality due to debris entanglement or ingestion is unlikely.

Foraging distances of a resident yellow-legged gull (Larus michahellis) population in relation to refuse management on a local scale

Seasonal fluctuations in marine prey availability aroundbreedingcoloniesareoneofthemajorfactorsaffecting resident behaviour in seabirds. This is particularly applicable to large gulls (Larus spp.). The effect of refuse management on large gulls has been studied chiefly in relation to breeding dynamics, but it is less understood with regard to movement patterns. Our aim was to test whether the closure of one large dump andtheuse offalconryto detergull access to two others, within the southeastern Bay of Biscay area, affected the forag- ing distance of local yellow-legged gulls (Larus michahellis). During a period of seven consecutive winters between 2005 and 2011, the proportion of gulls that moved less than 50 km from their natal site was 70 %. However, during the winter of 2010, when they were deterred from accessing refuse tips within the region, gulls were found to travel longer distances. This result was explained neither by a decreasing survey effort near colonies nor by a decrease in apparent availability of marine prey, thus supporting the hypothesis that refuse man- agement within the region influenced the movement patterns of local gulls.

Call for papers: Filth

From the Wellcome Collection’s 2011 exhibition Dirt: the filthy reality of everyday life , via Deutsche Borse Photography Prize 2012 nominee Pieter Hugo’s images of Ghanaian refuse tips, to Harmony Korine’s Trash Humpers (2010), filth is having its cultural moment. Filth has a wide range of material associations, including dirt, waste, rubbish, and the human body. Filth has moral connotations: of sexuality, but also in the context of political discourse. Filth is unstable and insidious; definitions of what constitutes filth are subjective and its boundaries are impossible to circumscribe.

Les haches perforées du Néolithique final. L’exemple de Saint-Blaise/Bain des Dames (canton de Neuchâtel, Suisse) : chaîne opératoire et analyse spatiale, des conclusions inédites

This article deals with a phenomenon peculiar to the Final Neolithic of the Western Swiss Plateau, the emergence of perforated hammer-axes of Corded-Ware influence. Analysis of the corpus from the lakeside settlement of Saint-Blaise “ Bains des Dames” (Lake Neuchâtel, Switzerland) provides new information about these emblematic objects. We can therefore propose new hypotheses regarding this subject in the context of the communities of this region, known as the Three-Lakes. The influence of the Corded-Ware Culture made itself felt at the eastern end of the Swiss Plateau during the second half of the third millennium BC. It then impacted ca. 2700 BC the Late Lüscherz Culture, which was established around the Three-Lakes. As a result of this meeting of cultures, the Auvernier Corded Ware Culture emerged. Houses remain essentially unchanged, but now have refuse tips at one end. The pottery shapes are progressively adapted to eastern models. At the same time, perforated hammer-axes are adopted and develop as a new prestige item. Only known from a few examples on the eastern Swiss sites, they are frequently manufactured in all the villages of the Three-Lakes region. The smaller versions of this artefact, however, have occasionally been considered by researchers as crude copies of those from the Corded-Ware Culture, or else as functional objects. At Saint-Blaise “ Bains des Dames”, hammer-axe production begins in the Early Auvernier Corded-Ware and attains a peak during the Late Auvernier Corded-Ware. Study of the chaîne opératoire shows that strict constraints were attached to the manufacture of these objects. The choice of raw material was restricted to a single variety of serpentinite, used in the form of cobbles. Furthermore, the manufacture of hammer-axes clearly required a greater know-how than that required for the everyday objects. We note that the failurerate is extremely high at every stage of the manufacturing process. Lastly, according to the spatial analysis, it would seem that the manufacture of hammer-axes took place in all the houses. The knowhow was thus mastered in each household. We are thus dealing with manufacture for personal use, undertaken at the household level yet subject to collective constraints. In fact, strong morphological similarities between objects indicate that standards were sometimes followed to within a millimetre. The adaptation of these norms to pebble size, ranging from 10-20 cm in length, explains variation in the size of the hammer-axes. These objects, far from being mediocre copies of an eastern model, are in fact the manifestation of a wellstructured autonomous system. The populations of the Three-Lakes fully adopted the hammer-axe, reinterpreting it to fit the constraints of the raw-material locally available. They thus turned it into an important object of prestige.

High importance of fish prey in the diet of Yellow-legged Gull Larus michahellis chicks from the southeast Bay of Biscay

The aim of the study was to describe Yellow-legged Gull Larus michahellis chick diet in the southeast Bay of Biscay. Sampling was carried out in three colonies (Ulía, Santa Clara, Guetaria) in Gipuzkoa, northern Iberia, during the breeding seasons of 2007 and 2008. Regurgitates (n = 70) were collected from chicks of c. 20 days old when they were ringed. Overall, 79 prey items were found, and each item was weighed and classified into one of the following prey-groups: marine (fish (Pisces), crab (Brachyura)), refuse tips (pork, beef, rabbit, chicken), terrestrial (earthworms (Lumbricinae), molluscs (Mollusca), insects (Insecta)), others (mainly vegetables or unidentified prey). The proportion of each prey-group did not differ from one year to the next and most prey was of marine origin (59.5%; all fish except for one crab), followed by refuse tips (22.8%), terrestrial (13.9%), and others (3.8%). These findings concur with those at colonies in northwest Iberia, and while local exceptions might occur, Yellow-legged Gull chick diet in northern Iberia is predominantly marine fish.

Analysing spatial and temporal variation in colony size: an approach using autoregressive mixed models and information theory

AbstractThe spatial and temporal variation in population sizes of animal colonies are rarely studied simultaneously. I examined factors determining colony size (number of nests) for 23 colonies from the only breeding population of rook Corvus frugilegus in Spain over 7 years. Population sizes within colonies were highly predictable over time, with autocorrelations up to a distance (lag) of 6 years. Autoregressive mixed models were used to explain colony size as a function of environmental factors, while controlling for temporal autocorrelation. These factors included refuse tips, widely used as food resource, and a derived variable that incorporated the two factors most often related to avian colony size (inter‐colony competition and foraging habitat around colonies). Autoregressive models provided a better fit to the data than models which did not consider temporal autocorrelation. The information‐theoretic (AICc‐based) approach revealed uncertainty in the selection of the best model explaining colony‐size, but relatively strong support for certain variables. The highest weights of evidence were for year (ωi = 0.90) and the number of competitors per unit of foraging habitat (i.e., derived variable; ωi = 0.63), showing that the size of rook colonies in Spain was negatively affected by inter‐colony competition relative to the foraging habitat surrounding the colonies. This variable measured within a 6‐km radius from the colonies had ~30 times higher weight of evidence (more plausible) than the same variable measured within 3 km, indicating that food limitation may occur outside the breeding period. Sizes of colonies tended to decrease when distance between the colony and the nearest refuse tip increased. There was some evidence supporting the idea that the effect of the number of competitors per unit of foraging habitat on colony size varied from year to year, but statistical power was weak. These findings suggest that variation in number of rook nests within colonies reflects spatial and temporal heterogeneity of net food via both inter‐colony competition and foraging habitat around the colony.

Population trends of Rooks Corvus frugilegus in Spain and the importance of refuse tips

Anthropogenic food from refuse tips can affect population dynamics in birds, especially gulls, but the evidence is mostly circumstantial. We combine analyses of long‐term population data and natural experiments to show a positive effect of refuse tips on the growth of the Spanish breeding population of Rooks Corvus frugilegus. In this isolated population of around 2000 breeding pairs, monitored since 1976, birds in colonies less than 10 km from tips fed largely on refuse, particularly during periods of lowest natural food availability. Three lines of evidence support the hypothesis that the supply of refuse influenced breeding numbers, suggesting that this population is limited by food: 1) between 1976 and 2003, the two population nuclei that had access to tips increased 2.1 and 3.7 times more than that without a tip nearby; 2) annual colony growth between 1996 and 2003 was strongly correlated with the availability of tips when other potentially important variables were taken into account; 3) the number of breeding pairs in refuse‐foraging colonies declined rapidly after the closure of the local tip and recovered only when a supply of refuse was restored. The effect of tips on colony growth was stronger when the availability of natural foraging habitat around the colonies was low, suggesting that anthropogenic food acts as a buffer against shortage of natural food. Artificial food supplementation may be an effective tool to increase the breeding population of target species, especially those facing a reduction of their foraging habitats. The potential effects on bird species of Directive 1999/31/CE, which is enforcing a massive closure of tips in Europe, are discussed.

Phosphine in the Urban Air of Beijing and Its Possible Sources

Both as an air pollutant and as a gaseous component of the local phosphorus cycle, phosphine (PH3) was found in the urban air of Beijing. Other possible sources, like paddy fields and water reservoirs, were selected for testing the hypothesis of the biological phosphine formation. Phosphine in the urban air of Beijing was measured in different seasons. In the summertime phosphine levels typically peak in the early morning and then decline towards noon. The maximum concentration at 6.00 am was 65 ng m−3 whilst that at noon was 11 ng m−3. In spring and in wintertime, the phosphine levels in the urban air of Beijing were lowest. A first screening revealed phosphine also in gas and in sediment samples from a paddy field near Beijing, the Beijing Shisanling water reservoir, and the refuse tips Changping of Beijing as well as in the ambient air adjacent to these sampling sites. The maximum phosphine concentrations in these gas samples were 41 (marsh gas, paddy field), 135 (marsh gas, reservoir), 1062 (landfillgas) ng m−3, and in the ambient air samples 146 (air, paddy field), 166 (air, reservoir), and 71 (air, refuse tips) ng m−3. In sediment samples, the highest matrix-bound phosphine levels were 13 (paddy field), and 3.9 (reservoir) ng kg−1. These comparatively high concentrations of the readily oxidizable phosphine in air indicate hitherto unknown but important phosphorus emission sources, which might reduce the biomass growth in Chinese fields and forests by a general phosphorus limitation. Phosphine is also a constituent of the air pollution in China. However, more work has to be done to evaluate the different sources of atmospheric phosphine.

Management implications of metal transfer pathways from a refuse tip to mangrove sediments

Mangroves have often been thought of as wasteland, and because of this attitude, many mangrove forests have been used as sites for refuse tips, sewage outfalls and as illegal dumping grounds. The transfer of metals from a refuse tip to mangrove sediments is investigated and four pathways of heavy metal migration are identified. These are direct seepage across the tip-cell floor to groundwater, tidal over-topping of the bund wall and capillary suction of leachates to groundwaters, direct seepage through the cell wall of leachates to surficial sediments, and surface runoff during rainfall events. Metal input by surficial runoff indicates that significant quantities of metals have been transferred to the mangroves via this mechanism. However, metal transfer via surface runoff is probably small in comparison to the other three mechanisms discussed. The variable nature of the transfer mechanisms operating, the variability in sediment texture both vertically and laterally, and the number of transfer pathways makes potential management of the site difficult. Any management plan for this site must consider both the feedback mechanisms that operate, and that the whole sediment column is involved in metal transfer.

Geographic variation of the winter diet of the Red Kite Milvus milvus in the Iberian Peninsula

This paper presents data on the winter diet of the Red Kite Milvus milvus in the Iberian Peninsula. The diet composition and its relationship with food abundance and habitat characteristics were studied in two areas (northern and southern plateaux) with different food availability and habitat composition. Red Kites showed a clear difference in diet between the two plateaux, with a higher consumption of carrion on the northern plateau and of game species on the southern plateau. Common Voles Microtus arvalis, despite being a very abundant prey on the northern plateau, did not appear in the diet in high numbers, but their frequency was related to the proportion of land occupied by nonirrigated (cereal) crops. High frequencies of “small” carrion (e.g. farmed Rabbits Oryctolagus cuniculus, poultry Gallus sp.) in the diet were correlated with a decrease in the trophic diversity which suggested an active choice of the food, at least in years with low vole densities. We suggest that the use of carrion is influenced not only by its abundance but by its availability to Red Kites. Refuse tips and muladares (dumps for dead livestock) and their management during the winter are important for the conservation of the species.

Population change among Pacific, kelp and silver gulls using natural and artificial feeding sites in south-eastern Tasmania

The kelp gull, Larus dominicanus, which is widely distributed around the southern hemisphere, has become established in Australia only in the past half-century. The greatest numbers of kelp gulls in Australia are now found in south-eastern Tasmania in sympatry with the two endemic species, the morphologically similar Pacific gull, L. pacificus, and the smaller silver gull, L. novaehollandiae. We examined populations of the three species in this area. We surveyed large refuse tips and specific shoreline sites in the Hobart area regularly during the winter months in 1981 and again in 1992, recording numbers of each species, and age classes of kelp and Pacific gulls. Between the two survey periods, the number of Pacific gulls and the total number of all gulls present at refuse tips remained unchanged. There was, however, a marked increase in the number of kelp gulls at tips, equivalent to an annual rate of increase of 22.8%, and a corresponding decrease in the number of silver gulls. Kelp gulls of all ages were over-represented at refuse tips, while adult Pacific gulls fed preferentially at more natural shoreline sites. At shoreline sites, adult Pacific gulls appeared to exclude kelp gulls from small bays in 1981, but kelp gulls were present in most of these bays eleven years later. Reducing access to food at refuse tips may be an effective means of controlling the kelp gull population in this area.

Trophic niche width and overlap of two sympatric gulls in the southwestern mediterranean.

The diets of two potential competitor species, Audouin's Larus audouinii and yellow-legged gulls Larus cachinnans, were examined while they bred at the Chafarinas Islands during 1993, 1994, and 1995. Data were collected during two commercial fishing regimes: (1) trawling and purse seine fisheries, and (2) diurnal trawlers only. Since the food supply for the gulls in this area was heavily reliant on the activity of purse seine fisheries, these contrasting situations allowed us to analyze short-term effects, induced by daily changes in food supply, on niche width, dietary shift, and niche overlap between the two species. Overall, both species relied mainly on fish for food, especially Clupeiforms, in the case of Audouin's gull irrespective of the fishing situation, and in the case of the yellow-legged gull, only when purse seine fishing was in operation. When purse seine boats did not operate (food shortage), yellow-legged gulls broadened their niche, consuming equal amounts of all the feeding resources, and they showed a dietary shift toward a greater consumption of prey from refuse tips. In contrast, Audouin's gulls did not change their niche width, but showed a slight dietary shift away from the consumption of epipelagic fish, compensated by an increase in reliance on benthic-mesopelagic resources. Niche overlap was clearly higher on days when both fishing fleets operated, probably because a superabundant food resource facilitates high overlap without affecting coexistence between the two species. Since our study was developed on the basis of daily variations in food supply, and competition effects are to be expected on a longer-term basis, these changes can be seen as the outcome of the coexistence of two species in stable competitive equilibrium.

Effects of trawler discard availability on egg laying and breeding success in the lesser black-backed gull Larus fuscus in the western Mediterranean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 132:43-46 (1996) - doi:10.3354/meps132043 Effects of trawler discard availability on egg laying and breeding success in the lesser black-backed gull Larus fuscus in the western Mediterranean Oro D The availability of trawler discards is likely to have a pronounced effect on the reproduction of seabirds, but this importance is normally difficult to quantify. A comparison between 2 breeding seasons of the lesser black-backed gull, one of them affected by a trawling moratorium, has allowed an assessment of the effects of discard availability on its egg laying. When trawlers operated, diet was dominated by fish from discards, while during the trawling moratorium gulls fed from refuse tips, olive tree fields and especially rice fields. Although neither breeding phenology was different nor was clutch size significantly lower in the year of the trawling moratorium, the volume of the eggs decreased significantly, showing the importance of trawler discard availability as a proximate determinant of egg production of scavenging seabirds. Since the moratorium overlapped with the chick rearing stages in both years, breeding success was probably lower than before the establishment of the trawling moratorium in 1991. However, the breeding success was higher in 1994 than in 1995, when the moratorium overlapped with the entire period of chick growth. Population dynamics of the species is probably affected by changes in trawler discard availability, especially if a trawling moratorium continues for many years. Trawler discards . Food availability . Moratorium . Lesser black-backed gull . Egg-laying . Population dynamics . Reproduction Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 132. Publication date: February 29, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

The influence of refuse tips on the winter distribution of Yellow-legged GullsLarus cachinnans

The influence of several variables on the abundance of wintering Yellow-legged Gulls was assessed in 20 randomly sampled districts in NE Spain. Refuse tips and fidelity to the breeding colonies explained most of the variation found. However, the effect of these factors was age-dependent, adults tending to stay closer to the main breeding colony on the Medes Islands and the proportion of juveniles in the population increasing with the distance from that colony. Gulls were distributed among refuse tips in proportion to refuse availability, which could be interpreted as refuse tips being the preferred foraging area for the population.

Occurrence of oocysts of Cryptosporidium sp. in Larus spp. gulls.

Between November 1990 and February 1991 101 gull faecal samples, collected in central Scotland, and 50 cloacal lavages, from gulls captured at two refuse tips near Durham, England were examined for the presence of Cryptosporidium sp. oocysts. Five of 101 (c 5%) of faecal samples and 11 of 50 (22%) of cloacal lavages contained oocysts, of which 64% and 83%, respectively were considered viable when examined with propidium iodide and 4'-6-diamidino-2-phenylindole. Since there is insufficient evidence to ascribe these oocysts to a recognized species they are therefore referred to as Cryptosporidium sp. oocysts. There were significant differences in the occurrence of oocysts between gulls captured at the different refuse tips (P < or = 0.01), but no significant difference between the distribution of oocysts in two species of gull, Larus argentatus (Herring Gull) and L. ridibundus (Black-head Gull). The differences may be explained by different food sources and feeding habits. The contribution of gulls to environmental contamination with Cryptosporidium sp. oocysts is probably generally small, but may be more significant when large numbers roost on surface waters.

Dynamics of weed populations in a northern subarctic community

The introduced flora of Churchill, northern Manitoba, was studied to draw some conclusions about the dynamics of weeds in northern subarctic communities in general. One hundred and six introduced species have been recorded at Churchill. Fifty-five percent of these were "temporary," dying out when original colonizers senesced (e.g., Avena spp., Setaria viridis). Seventeen percent were "established," i.e., able to set viable seed and maintain their populations (e.g., Thlaspi arvense, Crepis tectorum). Twenty-eight percent "persisted" locally by vegetative propagation or repeated seed input (e.g., Linaria vulgaris, Chenopodium album s.l.). The findings were compared with those of an earlier study. The number of species and their local distributions around Churchill have increased in the last 30 years. This may be due to an increase and diversification in the traffic with southern regions or to an amelioration in the climate. Although one in five species in the vicinity of Churchill are introduced, usually fewer than 12 weed species were established at any one site. Abandoned sites exhibited a rapid disappearance of weeds. Depauperate individuals of a few species were found away from inhabited areas, with none occurring in natural communities. Organic material in refuse tips provided a mild environment with a long growing season. Refuse tips may act as refuges for weeds and as potential sources of their seeds. Aliens that were successful at seed production were either perennials, winter annuals, or biennials. These plants flowered early and hence are able to ripen their seeds. Years with long growing seasons may allow seed production in otherwise temporary species. Dynamics of weedy species around Churchill will likely reflect current and (or) future events in other, more isolated northern communities. Key words: subarctic, weeds, introduced plants.

Use of Refuse Tips by Adult British Herring Gulls Larus argentatus During the Week

(1) The use of refuse tips by adult herring gulls was investigated using individually marked birds captured in Co. Durham and studied at Coxhoe refuse tip. (2) The pattern of work at the tip greatly influenced the time of gull feeding. Although they rarely fed when lorries were at the work face, they accepted the presence of a bulldozer. The main period of feeding was 12.00-12.30 h when the tip closed at lunch time. (3) On most days, the gulls were feeding for 30-60 min and it was estimated that an individual, on average, fed for < 20 min per day. It is thought that most gulls did not feed elsewhere on days when they visited Coxhoe tip. (4) There was considerable variation and overlap between the times of arrival and departure of adults. The maximum numbers counted at any time during the day represented an average of c. 58% of the number of individuals that actually visited the tip on that day. This percentage varied from 46 to 79% in different months. (5) The pattern of arrival and departure of birds appeared to be determined mainly by the working day rather than the duration of daylight. (6) Most adult herring gulls did not visit the tip on consecutive days and the average number of days they were present in the 5 main working days in the week ranged from 1 4 to 2 1 days during the year. (7) Only 34% of the gulls that visited the tip during a week were present on any one working day. Few of these used other tips in the area on days they were not at the study site. (8) Work finished at 12.00 h on Saturdays and the numbers declined rapidly once the refuse was covered and work ceased. About 30% of the gulls seen on Saturday were present on the previous day and 10% were seen on Saturday for the first time in the week. (9) It is calculated that if 509 constituted the peak number of adult gulls at any one time during a day, 840 individuals visited during the day and 2745 during the week.

A comparison of foraging at refuse tips by three species of gull (Laridae)

The comparative foraging of Black‐headed (Larus ridibundus), Herring (L. argentalus) and Great black‐backed gulls (L. marinus) was investigated at refuse tips in north‐east England. Between October and February, two races of Herring gulls are present, those which breed in Britain (L. a. argenteus) and the larger Scandinavian herring gulls (L. a. argentatus).Three types of feeding at a refuse tip were distinguished: undisturbed primary feeding (highly competitive feeding on freshly dumped rubbish), disturbed primary feeding (agile surface dipping for food from the air, close to the working bulldozer) and secondary feeding (low density feeding on dispersed and partially buried rubbish).In undisturbed feeding the largest individuals (i.e. Great black‐backed gulls) were competitively superior and achieved the highest feeding success. The smallest individuals (i.e. Black‐headed gulls) were rapidly excluded by the larger gulls. Scandinavian herring gulls were competitively superior in intraspecific interactions, but they were selectively attacked by Great black‐backed gulls. Disturbed feeding, in contrast, was used most by Black‐headed gulls and not at all by Great black‐backed gulls. Large body size is a disadvantage in disturbed feeding, due to increased wing loading acting as a constraint on manoeuvrability. Overall, the separation between species, in terms of the proportion of food gained by different feeding methods, was estimated at 30–50%.Cold and windy conditions led to increased numbers of Herring and Great black‐backed gulls at tips, and numbers of Great black‐backed gulls were also higher when fish landings at the coast were low. There were significant differences between tips in the number of Great black‐backed and Black‐headed gulls, possibly due to differences in working regime which influence the feeding opportunities which were available.

Changes in the gull populations of SW Wales

The breeding populations of the Larus gulls in SW Wales are reviewed, using all the available information hut specifically drawing on the data from the islands of Skomer, Skokholm, St Margarets and Caldey. After increasing steadily for many years, Herring Gull numbers have recently declined rapidly. Some populations of Great Black-backed Gulls have been greatly affected by deliberate control measures but the records show a similar pattern to that of Herring Gulls, with large decreases being recorded recently despite the lifting of these controls. The decreases in the populations of these species are coincident with botulism poisoning of adult birds during the breeding season, probably resulting from feeding on refuse tips. There may be a connection between the introduction of black plastic bags for refuse collection and the outbreak of botulism in SW Wales. Lesser Black-backed Gull populations continue to increase at a rate that has been roughly constant for at least 15 years. This species rarely feeds at...

Salmonella Carriage By Herring Gulls in the Clyde Area of Scotland in Relation to Their Feeding Ecology

(1) Between February 1982 and February 1984, 2985 herring gulls, captured at refuse tips in the Clyde area, were examined for the presence of salmonellae in their faeces; 9.2% of those examined in the breeding season were found to be carrying salmonellae, and 9.8% during the non-breeding season. The most common serotypes isolated were Salmonella virchow and S. typhimurium. (2) The proportion of these herring gulls carrying salmonellae was significantly positively correlated with the incidence of salmonellosis in the human population in the same area at the same time, and presumably reflects the level of environmental contamination. (3) There were no statistically significant differences in carriage rates between different age classes of herring gull, but during the non-breeding season, there was a highly significant difference between the sexes. The rate of female carriage at this time was more than double that of males, and appears to reflect differences in their feeding ecology. (4) A further 163 herring gulls obtained from breeding colonies were similarly examined. These had a significantly higher carriage rate than those examined at refuse tips at the same time, indicating that other kinds of feeding areas may give rise to more frequent infection of gulls. (5) There was no evidence that infection with salmonellae affected the health of the gulls concerned. Such pathogen carriage by gulls, when coupled with their considerable powers of dispersal, may give rise to potential public health problems, particularly when gulls are roosting on potable water supplies.