Robert T. Barrett

The food requirements and ecological relationships of a seabird community in North Norway

Almost all species of seabirds at Horney and Reinoy are increasing in numbers. The Herring Gull colony is one of the largest in Europe. Most species feed mainly on capelin, but sandeels are important for Briinnichs Guillemots, Razorbills and Shags. Diets remained closely similar from year to year but consistently differed between species. Puffins and Razorbills fed largely on immature fish while other species took mostly two year old fish. The majority of the two year old capelin consumed by auks in June and July were ripe, although most capelin spawn in March and April. Foraging ranges were extremely short, breeding success and chick growth rates unsually high. Food consumption totalled 9000 tonnes yr-1, of which 7500 tonnes were capelin. Food appeared to be superabundant, and dietary differences between species probably reflect anatomical and behavioural adaptations rather than niche partitioning through active competition. Seabirds appear to select capelin of high lipid content since they fed predominantly on ripe two year old fish during chick-rearing, when spent fish were of poorer nutritional value.

Measurements and weight changes of norwegian adult puffins fratercula arctica and kittiwakes rissa tri dactyl a during the breeding season

There was a steady increase with latitude in the size of Puffins and Kittiwakes breeding in Norway. Data which supports earlier suggestions to disregard the subdivision of F. arctica arctica and F. a. grabae are presented. Males of both species were consistently heavier and larger than females in measurements of wing length, head length, bill length and bill depth. Discriminant analyses showed that head length, sometimes combined with bill depth, distinguished the sexes most precisely. Both sexes of both species steadily lost weight from the start of incubation to the peak chick feeding period. It is argued that this weight loss is voluntary and adaptive.

LEVELS AND TEMPORAL TRENDS (1983-2003) OF POLYBROMINATED DIPHENYL ETHERS AND HEXABROMOCYCLODODECANES IN SEABIRD EGGS FROM NORTH NORWAY

The present study assessed temporal trends (1983-2003) of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in eggs of herring gulls (Larus argentatus), Atlantic puffins (Fratercula arctica), and black-legged kittiwakes (Rissa tridactyla) in North Norway. Generally, PBDE concentrations increased between 1983 and 1993 and then leveled out, although species-specific trends were reported. Levels of alpha-HBCD increased in all species throughout the 20-year period. Levels of nona-BDEs and BDE 209 ranged from nondetectable to parts per billion. Nevertheless, highly variable procedural blanks were reported for the nona-BDEs and BDE 209, which clearly illustrates the importance of including blanks repeatedly during determination of these compounds.

The variability of biometric measurements

Barrett, R. T., M. Peterz, R. W. Furness and J. Durinck. 1989. The variability of biometric measurements. Ring. & Migr. 10: 13–16. Within and between measurer consistency of measurement of auk biometrics was examined. We point out variations between individuals that may equal reported differences between populations.

Prevalence and diversity of Lyme borreliosis bacteria in marine birds.

A potential role of seabirds in spreading Lyme disease (LB) spirochetes over large spatial scales was suggested more than 10 years ago when Borrelia garinii was observed in marine birds of both hemispheres. Since then, there have been few studies examining the diversity of Borrelia spp. circulating in seabirds, or the potential interaction between terrestrial and marine disease cycles. To explore these aspects, we tested 402 Ixodes uriae ticks collected from five colonial seabird species by amplification of the flaB gene. Both the average prevalence (26.0%+/-3.9) and diversity of LB spirochetes was high. Phylogenetic analyses grouped marine isolates in two main clades: one associated with B. garinii and another with B. lusitaniae, a genospecies typically associated with lizards. One sequence also clustered most closely with B. burgdorferi sensu stricto. Prevalence in ticks varied both among seabird species within colonies and among colonies. However, there was no clear association between different Borrelia isolates and a given seabird host species. Our findings indicate that LB spirochetes circulating in the marine system are more diverse than previously described and support the hypothesis that seabirds may be an important component in the global epidemiology and evolution of Lyme disease. Future work should help determine the extent to which isolates are shared between marine and terrestrial systems.

Shags (Phalacrocorax aristotelis L.) as potential samplers of juvenile saithe (Pollachius virens (L.)) stocks in northern Norway

Abstract Accurate measurements of the recruitment levels into any fish stock are essential for the successful management of that stock. Pollachius virens is an important commercial species in Norway but accurate determinations of the fecundity rate of the stock are nearly unfeasible. This is due to the inshore habitat of the youngest year classes of the species where they evade capture in traditional sampling gear. This paper proposes annual analyses of Phalacrocorax aristotelis summer prey harvest as a supplement to data collected during traditional fisheries surveys.

EFFECT OF INVESTIGATOR DISTURBANCE ON THE BREEDING SUCCESS OF THE BLACK-LEGGED KITTIWAKE

Abstract The effect of investigator activity on Black-legged Kittiwakes (Rissa tridactyla) was assessed using the disturbance caused by an ongoing intensive study investigating chick growth and adult mass loss. Though the effects were small, investigator disturbance decreased adult nest attendance and increased daily chick loss rates. Whereas overall chick survival until day 18 post-hatch was significantly lower in the high-disturbance plot in the first year of the study, it was substantially higher in the second year. We hypothesize that changes in predator activity as an indirect consequence of disturbance were responsible for this pattern. Herring Gulls (Larus argentatus) which nested near the high-disturbance plot and are the main predator of kittiwakes in our study area may have been more susceptible to the effect of disturbance than the kittiwakes themselves. There was otherwise no statistically significant impact of disturbance on chick growth, or on adult kittiwakes extending into the following year. Biases in studies of kittiwakes due to investigator disturbance may thus be negligible when the study is carefully designed. Future studies investigating effects of disturbance on birds should, however, include data concerning potential predators of the focal species and include more than one low-disturbance plot, and should be carried out over two or more years.

When things go wrong: intra‐season dynamics of breeding failure in a seabird

During breeding, long-lived species face important time and energy constraints that can lead to breeding failure when food becomes scarce. Despite the potential implications of intra-season dynamics in breeding failure for individual behavior, carry-over effects, dispersal decisions and population dynamics, little information is currently available on these dynamics at fine temporal scales. Here, we monitored the foraging behavior and the proportion of successful black-legged kittiwake pairs from nest construction to chick fledging in a colony of the southern Barents Sea, to relate foraging effort to the dynamics of breeding failure over an entire breeding season, and to infer the environmental conditions leading to this failure. Specifically, we tracked kittiwakes with GPS and satellite tags during incubation and early chick-rearing to document nest attendance, foraging range, time budgets and daily energy expenditures (DEE). We also monitored diet changes over time. We predicted that breeding failure would follow a non-linear trend characterized by a break point after which breeding success would drop abruptly and would be related to a substantial increase in foraging effort. Kittiwakes showed contrasting foraging patterns between incubation and chick-rearing: they extended their foraging range from 20 km during incubation to more than 450 km during chick-rearing and switched diet. They also increased their DEE and readjusted their time budgets by increasing time spent at sea. These changes corresponded to a break point in breeding dynamics beyond which the proportion of successful pairs abruptly dropped. At the end of the season, less than 10% of kittiwake pairs raised chicks in the monitored plots. This integrative study confirms that breeding failure is a non-linear process characterized by a threshold beyond which individuals face an energetic trade-off and cannot simultaneously sustain high reproductive and self- maintenance efforts. In this way, the occurrence of sudden environmental changes complicates our ability to predict population dynamics and poses conservation challenges.

Optimal foraging in chick-raising Common Guillemots (Uria aalge)

The Norwegian population of the Common Guillemot Uria aalge has declined by >95% since the 1960s, and is classified as critically endangered in the Norwegian Red List. Much of the recent decline has been attributed to reduced food availability, but without extensive documentation of adult diet. Instead, chick diet has been considered a proxy of adult diet during the breeding season in many Norwegian studies. However, central-place foraging theory, especially for single-prey loaders, predicts that this may not be so, and this study directly compares the diet of adult and chick Common Guillemots during the breeding season at a colony in NE Norway. Whereas chicks were fed mainly capelin (Mallotus villosus) and sandeels (Ammodytes sp.), most of the adult diet consisted of the two youngest year classes of Gadidae, probably cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). A successful ecosystem management of seabirds is dependent on a full understanding of how prey quality, abundance and availability influence seabird populations and their viability, such that knowing the true diet of adult Common Guillemots has important implications in the modelling and management of the Norwegian populations.

Prey Selection by Gannets at Breeding Colonies in Norway

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