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In sexually monomorphic animal species it is difficult to sex unknown individuals. The most widely used method of sexing in those cases is discriminant analysis. In species that are socially monogamous and have biparental care, however, there exists another method which utilises the intra-pair difference in the trait used in sexing. Equations for calculating the fraction of wrongly sexed individuals using both methods are given and used to show that the latter method is more exact than discriminant analysis. The advantages and limits of both methods are compared. Field data from the kittiwake (Rissa tridactyla) are used to exemplify the intra-pair comparison method, and to test the assumptions underlying this method for this species. Among other things, it is shown that kittiwakes display random mating with respect to head+bill length. Sexing kittiwakes at Hornøya, northern Norway, by intra-pair differences in head+bill length gives correct results in 96% of the cases.

Toponyms of Tyrol – how to apply the endonymic principle in a highly diverse namescape Tyrol has an extraordinary diversity of toponyms, which is due to the various languages that have been and are spoken in this moun­tainous area. After presenting the «namescape» of Tyrol (North Tyrol, East Tyrol, South Tyrol and Trentino), the article addresses the challenges that the toponymy of Tyrol poses for the official Norwegian spelling norm and identifies two problems. First, the spelling of the landscape itself («Tyrol») is incompatible with the endonymic principle (which demands «Tirol»). Second, most toponyms of South Tyrol are currently normalised in their Italian forms. However, the endonymic principle suggests that the norm should allow all forms that are locally well-established. A coherent alternative to the current Norwegian spelling norm is suggested. Further recommendations are given regarding the Norwegian spelling of Tyrolean toponyms that are not covered by the official norm.

Impact or risk assessments of alien species can use qualitative criteria (such as verbally described categories) or quantitative criteria (numerically defined threshold values of empirically measurable quantities). According to a common misconception, the use of qualitative criteria in invasion biology is justified by uncertainty in the available data. Yet qualitative criteria have the effect of increasing uncertainty. In contrast, assessments using quantitative criteria are testable, transparent, highly repeatable and comparable. Most of these characteristics do not even depend on the availability of numerical data. Although quantitative criteria do not necessarily make assessments correct, they do make them correctable, which is the benchmark of science.

Abstract 1. Due to globalisation, trade and transport, the spread of alien species is increasing dramatically. Some alien species become ecologically harmful by threatening native biota. This can lead to irreversible changes in local biodiversity and ecosystem functioning, and, ultimately, to biotic homogenisation. 2. We risk‐assessed all alien plants, animals, fungi and algae, within certain delimitations, that are known to reproduce in Norway. Mainland Norway and the Arctic archipelago of Svalbard plus Jan Mayen were treated as separate assessment areas. Assessments followed the Generic Ecological Impact Assessment of Alien Species (GEIAA) protocol, which uses a fully quantitative set of criteria. 3. A total of 1,519 species were risk‐assessed, of which 1,183 were species reproducing in mainland Norway. Among these, 9% were assessed to have a severe impact, 7% high impact, 7% potentially high impact, and 49% low impact, whereas 29% had no known impact. In Svalbard, 16 alien species were reproducing, one of which with a severe impact. 4. The impact assessments also covered 319 so‐called door‐knockers, that is, species that are likely to establish in Norway within 50 years, and 12 regionally alien species. Of the door‐knockers, 8% and 10% were assessed to have a severe and high impact, respectively. 5. The impact category of most species was driven by negative interactions with native species, transformation of threatened ecosystems, or genetic contamination. The proportion of alien species with high or severe impact varied significantly across the different pathways of introduction, taxonomic groups, time of introduction and the environments colonised, but not across continents of origin. 6. Given the large number of alien species reproducing in Norway and the preponderance of species with low impact, it is neither realistic nor necessary to eradicate all of them. Our results can guide management authorities in two ways. First, the use of quantitative assessment criteria facilitates the prioritisation of management resources across species. Second, the background information collected for each species, such as introduction pathways, area of occupancy and ecosystems affected, helps designing appropriate management measures.

Seabirds breed in high density colonies, but the factors determining colony position aren't clear. Here, Sandvik et al. show that small-scale coastal topography is related to likely variation in fish larval abundance, which predicts the distribution of seabird colonies along the Norwegian coast.

Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.