Pathological features in marine birds affected by the prestige's oil spill in the north of Spain

A total of 2,465 seabirds, mainly common murres (Uria aalge), razorbills (Alca torda), and puffins (Fratercula arctica) that beached in the northwestern part of Spain after the "Prestige" oil spill on 19 November 2002 were examined by pathological methods. Birds were divided into three groups: dead birds with the body covered (group 1) or uncovered (group 2) by oil and birds recovered alive but which died after being treated at a rescue center (group 3). The main gross lesions were severe dehydration and emaciation. Microscopically, hemosiderin deposits, related to cachexia and/or hemolytic anemia, were observed in those birds harboring oil in the intestine. Severe aspergillosis and ulcers in the ventriculus were found only in group 3 birds, probably because of stress associated with attempted rehabilitation at the rescue center. The mild character of the pathological changes suggests that petroleum oil toxicosis causes multiple sublethal changes that have an effect on the ability of the birds to survive at sea, especially weak and young, inexperienced animals. Dehydration and exhaustion seem to be the most likely cause of death.     

Variation in the correction factor used for converting counts of individual Guillemots Uria aalge into breeding pairs

The correction factor k (breeding pairs/total count of birds) was measured for two nesting groups of Guillemots Uria aalge over 6–7 years. The value varied between different subgroups but there were no significant differences between groups or between years. These results, and those from other studies, suggest that a value of 0–67 is applicable to a range of colonies. Values of k for Razorbills Aha tarda were more variable. A plea is made for the presentation of original counts rather than 'corrected' figures in published work.     

Survival and non-breeding of adult Common Guillemots Una aalge

Annual survival of colour-ringed Common Guillemots Uria aalge with at least 1 year of breeding experience was measured in five study areas on the Isle of May, southeast Scotland from 1982 to 1993. Annual survival averaged 94.9%. There were no significant sex, year or area differences. Between 5% and 10% of the birds known to be alive in any year did not breed, and on average such birds appeared to survive less well (87%) than breeders (95%). Non-breeding did not occur randomly within the population, and 6% of birds accounted for 47% of the cases of non-breeding. It appeared that non-breeding in Common Guillemots on the Isle of May was socially induced with most cases occurring after an individual had lost its site.     

Mixed-function oxidase activity in seabirds and its relationship to oil pollution

1. The hepatic activity of epoxide hydrolase, aldrin epoxidase, aminopyrine N-demethylase, 7-ethoxyresorufin O-deethylase, benzo(a)pyrene 3-hydroxylase and UDP glucuronyl transferase was determined in adult herring gulls (Larus argentatus) at various stages of the breeding season. 2. MFO activity was measured for adult Leach's storm-petrels (Oceanodroma leucorhoa), guillemot (Uria aalge) and Atlantic puffins (Fratercula arctica). For most assays the values were highest for the puffin. 3. MFO activity in both nestling and adult Atlantic puffins was determined. The degree of induction caused by a single internal dose of Prudhoe Bay crude oil in adult puffins and that caused by multiple internal doses in nestling puffins was measured.     

The genetics of bridling in guillemots from a study of hand-reared birds

The guillemot ( Uria aalge ) is a dimorphic species in the Atlantic part of its range with both a normal and a "bridled" form. The results of hand-rearing guillemots of known parentage are compatible with bridling being a recessive variant from the normal, carried by a single gene on one of the autosomes. The first definite signs of bridling were seen as early as 54–66 days after hatching. There was no significant difference between the bridled and normal variants in the body weight and wing length of breeding adults and egg weight and hatching weight of the young. The likelihood of physiological differences between the two variants and also the factors determining morph-ratio and its changes with time are discussed.     

A technique which may allow accurate determination of the age of adult birds

Although many age determination techniques have been developed for four of the five vertebrate classes, none has been developed to determine ages of adult birds. Here we report a technique, involving counting endosteal layers in the tibia, that has allowed us accurately to determine the age (in years) of 12 dead birds of species in four different families, Fulmar Fulmarus glacialis, Shag Phalacrocorax aristotelis, Redshank Tringa totanus and Great Skua Catharacta skua, all of which had been ringed as chicks and so were of known ages up to 16 years old, but provided inaccurate results for one species, the Common Guillemot Uria aalge. Since other bird species have been found to possess endosteal layers and no species has yet been found to lack such layers, this would appear to be a technique of general applicability which could permit invaluable new work in both pure and applied fields of ornithology.     

Sampling avian adipose tissue: assessing a nondestructive biopsy technique

ABSTRACT.   Adipose tissue samples can provide valuable information about the physiology, foraging ecology, and toxicology of birds. However, despite these varied applications, to date, no procedure for taking adipose samples from live birds has been described in detail, nor assessed for potential adverse effects. We describe a nonlethal method for collecting adipose tissue from adults and chicks of Black-legged Kittiwakes ( Rissa tridactyla ), Common Murres ( Uria aalge ), and Northern Fulmars ( Fulmarus glacialis ), and assess the short- and longer term effects of the procedure. Biopsies were carried out in the field using topical anesthetic and samples were taken from the synsacral region. Only two of 283 birds sampled (0.7%) had too little adipose tissue to be sampled successfully. Thirty-two kittiwakes were recaptured at varying intervals after the procedure (3–50 d) and the biopsy site inspected carefully. No signs of infection were observed and wounds healed completely within 6 d. Compared to birds captured for routine banding, biopsied kittiwakes showed neither greater weight loss nor reduced breeding success in the year of sampling. Similarly, recapture rates of biopsied birds in subsequent years were similar to those of individuals that had been blood sampled or banded. Our results suggest that collecting samples of adipose tissue by nondestructive biopsy has no more effect on birds than taking blood samples via syringe. Thus, we recommend nondestructive adipose tissue sampling via biopsy as an effective alternative to lethal methods in studies of wild birds.     

Dispersal and distribution of the tick Ixodes uriae within and among seabird host populations: the need for a population genetic approach

The aim of this study was to characterize the spatial distribution of the tick Ixodes uriae within and among populations of its seabird hosts and to consider the potential insight that could be gained by a population genetic approach to the issue of dispersal of this tick. Analyses of data collected around the Avalon Peninsula, Newfoundland, indicated that both the prevalence and mean abundance of ticks varied significantly among sample locations. Whereas ticks were found on all 4 host species examined (Rissa tridactyla, Uria aalge, Alca torda, Fratercula arctica), infestation prevalence and mean abundance differed among the species. On R. tridactyla, ticks were significantly aggregated at the among-nest scale and nestling infestation was spatially autocorrelated. Conversely, ticks were not aggregated among chicks within nests. These results enabled us to make a priori predictions regarding tick dispersal and host specificity and suggest there may be spatial structure of Ixodes uriae populations at both macro- and microgeographic scales. Investigating the population genetic structure of ticks within and among populations of hosts with different breeding biologies should provide direct insight into the metapopulation dynamics of such a spatially structured system.     

Intercolony movement and behaviour of immature Guillemots Uria aalge

A minimum of 61 Guillemots Uria aalge ringed as chicks at other colonies was recorded at the Isle of May between 1987 and 1991 (four prior to 1990, six in 1990, 51 in 1991). Two were adults and 59 were immatures. Most of the British and Irish colonies where many chicks had been ringed were represented. Higher proportions of birds ringed at colonies relatively close to the Isle of May were observed compared to birds ringed at more distant sites. Visitors ranged in age from 2 to 5 years, with single 10- and 14-year-olds. Relatively fewer 2- and 5- than 3- and 4-year-old birds were seen. Visiting birds were usually recorded once only, significantly less often than native immatures of the same age, except for 2-year-olds. The proportion of birds occupying sites on intertidal rocks as against sites in the colony appeared to be higher compared with native birds of the same age. Visiting birds formed a substantial proportion of the immature population. Ten immature birds from the Isle of May were recorded elsewhere. Four of these had been seen on the Isle of May previously, and four were seen there subsequently. A 6-year-old hatched at Sumburgh ( c. 420 km by sea) bred at the Isle of May in 1992.     

Isotopic segregation between sympatric seabird species increases with nutritional stress

Dietary segregation is essential for the coexistence of closely related species of animals. However, little is known about how changes in availability of food resources might affect trophic interactions of wild animals breeding in sympatry. Here, we examined how interannual variations in relative food availability (as reflected in blood levels of stress hormone corticosterone, CORT) affect food partitioning (assessed via a comparison of stable isotope δ(15)N and δ(13)C ratios of blood) between the common murre (Uria aalge) and thick-billed murre (Uria lomvia), breeding on a single colony in the Bering Sea. During a 6-year study, CORT varied among years but not between species, whereas stable isotope ratios varied among years and between species. Isotopic distance between species increased with increasing CORT. These results indicate that, when food was not limiting, both species relied on similar food resources. As foraging conditions deteriorated, murres diverged in their diets. We conclude that the degree of dietary segregation between Uria spp. varies with changes in the availability of food and is greatest during food shortages.     

A comparative study of the diet of auks killed during an oil incident in the Skagerrak in January 1981

Stomach contents were examined from guillemots Uria aalge (Pont.), Razorbills Alca torda Linnaeus and Little auks Alle alle (Linnaeus) killed by oil in the Skagerrak in January 1981. The range of prey species was small; the commonest fish found in the stomachs were Gobiusculus flavescens (Fabricius), Crystallogobius linearis (Düben), Sprattus sprattus (L.), Trisopterus minutus (L.) and Ammodytes sp. The relative importance of these fish depended on bird species and locality. Guillemots contained gadoids more frequently and sandeels less frequently than razorbills, and the composition of guillemot samples from Oslo Fjord differed from that of samples from Sweden. Invertebrate remains were uncommon in all bird species; the commonest items recorded were polychaete jaws. The frequency of occurrence of items in the diet of guillemots from Oslo Fjord was apparently influenced by the extent of oiling suffered by the birds.     

Non-random, intra-colony distribution of bridled guillemots Uria aalge

Within the Common guillemot Uria aalge colony, at the Gannet Clusters, Labrador, Canada, there was no evidence of heterogeneity in the proportion of bridled birds in different parts of the colony. Nor was there any evidence for assortative mating among bridled guillemots. Examination of the distribution of bridled birds in rows of guillemots however, showed a significant degree of clumping. Two hypotheses are presented to explain this distribution pattern: (a) the environmental hypothesis, which proposes that bridled birds preferentially select particular micro-habitats, or choose to breed where there are already bridled birds. (b) the return hypothesis, which proposes that one sex (probably female) returns to breed very close to where it was reared.     

Long-term changes in breeding phenology at two seabird colonies in the western North Sea

There is compelling evidence that the breeding phenology of many species has changed substantially in recent decades. However, taxonomic and spatial variation in the direction and rate of change is still not well understood. We explored these issues by analysing a dataset containing information on first egg dates of 10 species of seabird at two major breeding colonies (86 km apart) in the western North Sea over a period of 35 years. Within a species, timing of breeding was positively correlated between the two colonies, suggesting that factors affecting the phenology of these species operated at a regional rather than a colony scale. Comparison of time trends among the species revealed contrasting patterns, with some showing no systematic change, others becoming earlier and others later. The clearest species groupings appeared to be among the terns with arrival and/or first egg dates becoming earlier in Arctic Terns Sterna paradisaea , Common Terns Sterna hirundo and Sandwich Terns Sterna sandvicensis , and among the auks (Common Guillemot Uria aalge , Razorbill Alca torda and Atlantic Puffin Fratercula arctica ) and Black-legged Kittiwake Rissa tridactyla where the trend was in the opposite direction towards later breeding. This general trend towards later breeding in the latter group of species contrasts with correlational evidence from many other organisms indicating that breeding phenology is advancing in response to climate change.     

Identifying the spatial scale of density-dependent interaction of predators with schooling fish in the southern Labrador Current

Previous work along the coast of Newfoundland has shown that aggregative responses of puffins, Fraiercula arctica , and common guillemots, Uria aalge , to schooling fish, primarily capelin, Mallotus villosus , occur at spatial scales of 2-6 km. The present work tests the hypothesis that coastal upwelling results in aggregation of capelin at this scale, and that the scale of interaction with predators can be predicted from wind-driven coastal upwelling. An observational experiment in 1987 showed that a relatively simple physical model could be used to predict the spatial scale of upwelling, that schooling fish aggregate at this scale after upwelling, that aggregation of schooling fish at the scale of upwelling decays as upwelling relaxes, and that the spatial association of puffins and guillemots with schooling fish reaches a maximum at this scale. These results suggest that relatively simple physical theory can, in some cases, be used to identify the spatial scale of interaction of predators with prey.     

No evidence of extra-pair paternity in the little auk Alle alle

Extra-pair paternity is typically rather infrequent in seabirds, as in most other long-lived and socially monogamous birds. Here we report the first paternity study of the little auk Alle alle , a high arctic seabird which raises only a single chick per year. Parentage was determined using three highly polymorphic microsatellite markers. We found that all 26 chicks in our sample were true genetic offspring of their social parents, with an upper 95% confidence limit of 10.88% for the frequency of extra-pair paternity. This level of extra-pair paternity is not significantly different from frequencies reported from the closely related common Uria aalge and Brünnich's guillemots U. lomvia .     

Site use and fidelity in the Common Guillemot Uria aalge

The site fidelity of 470 colour-ringed Common Guillemots Uria aalge with at least 1 year of breeding experience was followed on the Isle of May from 1982 to 1993. On average, 85.7% of birds recorded breeding at a site in any year were present at the same site in the following season. Of those which did not retain their site, 35% had moved to another site, 25% were nonbreeders and 40% were not seen. Site- fidelity of birds which returned to the colony the next year was 91%. There were no significant age or sex effects, but there were significant (and unexplained) year and area effects. Most birds which changed sites moved less than 2 m. Some birds which obtained a new site improved their nesting success, but many others became nonbreeders; it is speculated that the former chose to move site, whilst the latter had been evicted.     

The effects of variable foraging conditions on common murre (Uria aalge) corticosterone concentrations and parental provisioning

This study investigated how total corticosterone concentrations, chick-feeding rates, and adult body mass changed with food availability from 1998 to 2000 in the same individually marked common murres (Uria aalge). Capelin, the main prey species, arrived inshore by the onset of murre chick hatching in 1998 and 1999 (prey match years); whereas in 2000, hatching began approximately 1 week before the capelin arrived inshore to spawn (prey mismatch year). Serum corticosterone concentrations were higher in the same individuals in the prey mismatch year than they were in either of the match years. Birds sampled before peak capelin spawning in the mismatch year had higher corticosterone levels than murres sampled after peak spawning. Murres with higher corticosterone levels had higher chick-feeding rates and less mass loss in the mismatch year (compared to the match year 1999) than birds with lower levels. Corticosterone levels did not differ between birds that had not foraged for at least 12 h (brooded chick overnight) and those that had, suggesting that short-term food deprivation did not affect corticosterone concentrations. Taken together, these findings suggest that the difference between years reflects a baseline shift in corticosterone levels, particularly in the high-quality birds that were able to increase both corticosterone concentrations and foraging effort.     

The post-fledging survival of young Guillemots Uria aalge in relation to hatching date and growth

The post-fledging survival of a total of 1277 young Guillemots Uria aalge ringed in 6 years was assessed using sightings of 267 individuals back at the natal colony and recoveries of 46 ringed birds. In two years there was a significant decline in survival prospects with estimated hatching date, the first time such a trend has been demonstrated in the Alcidae. In these years pairs breeding early had a 2–3 times greater chance of having a young survive to return to the colony than pairs breeding three weeks later. Hatching date had no effect on survival prospects in the other four seasons and in none of the years did chick body condition have a demonstrable effect on post-fledging survival.     

Effect of observer differences on abundance estimates of seabirds from ship-based strip transect surveys

Data from four ship-based strip transect surveys of seabirds, in which six observer teams from several countries cooperated, were used to estimate observer differences. The numbers of birds per sampled area as reported by the various observer teams were used to estimate differences among observer teams. As overlap in effort was not complete (all teams did not work in exactly the same areas at the same times), a log-linear model was used to correct for differences due to survey and region effects and the state of the sea. Considerable observer differences were found. For example, three teams out of five observed less than 16% of Guillemot Uria aalge and even less than 10% of Kittiwake Rissa tridactyla relative to the team that reported the highest densities.     

Reproductive senescence in a long-lived seabird: rates of decline in late-life performance are associated with varying costs of early reproduction

Evolutionary theories of senescence predict that rates of decline in performance parameters should be shaped by early-life trade-offs between reproduction and somatic maintenance. Here we investigate factors influencing the rate of reproductive senescence in a long-lived seabird, the common guillemot Uria aalge, using data collected over a 23-year period. In the last 3 years of life, individual guillemots had significantly reduced breeding success and were less likely to hold a site or attempt to breed. Females senesced at a significantly faster rate than males. At the individual level, high levels of reproductive output earlier in life were associated with increased senescence later in life. This trade-off between early- and late-life reproduction was evident independent of the fact that as birds age, they breed later in the season. The rate of senescence was additionally dependent on environmental conditions experienced earlier in life, with evidence that harsh conditions amplified later declines in breeding success. Overall, individuals with intermediate levels of early-life productivity lived longer. These results provide support for the antagonistic-pleiotropy and disposable-soma theories of senescence and demonstrate for the first time in a wild bird population that increased rates of senescence in reproductive performance are associated with varying costs of reproduction early in life.