annanil

• Molværsmyr, Sindre; Arnberg, Mie Prik; Helberg, Morten; Breistøl, Arild; Christensen-Dalsgaard, Signe & Moe, Børge [Vis alle 10 forfattere av denne artikkelen] (2026). A novel non-permanent attachment method for bird-borne tracking devices using 3D-printed clamps. Journal of Ornithology. ISSN 2193-7192. 167, s. 919–930. doi: 10.1007/s10336-025-02353-6. Fulltekst i vitenarkiv Vis sammendrag

  Collecting GPS positions on bird movements requires secure and efficient attachment methods that maintain animal welfare. For seabirds, one of the most threatened bird groups globally, non-permanent attachment methods are often preferred in short-term studies due to their lower risk of injury, feather damage, or long-term behavioral disruption. However, most available non-permanent solutions, such as tape or temporary adhesives, fail to stay attached for extended periods, often resulting in device loss within days or weeks. Here, we present a novel 3D-printed clamp design for attaching small solar-powered GPS devices to seabirds. The clamp and device were attached to the bird's feathers using only glue, with the clamp specifically designed to interlock with the device. This interlocking mechanism effectively sandwiches the feathers between the clamp and the device, ensuring a secure connection through the use of glue. The clamps were designed to maximize solar panel exposure and minimize premature detachment. We deployed 86 GPS devices on six seabird species across seven locations in Norway from 2023 to 2024, using device-specific clamp variants for attachment to mantle or tail feathers. Devices remained attached for an average of 39 days on mantle feathers (77 birds) and 77 days on tail feathers (four birds), providing sufficient deployment durations to monitor key life stages, such as incubation and chick-rearing. The weight of the clamp structure ranged from 0.5 to 3.2 g, depending on the variant, and emphasis was placed on keeping the total attachment weight as low as possible. The clamps were low-cost, easy to produce using standard 3D printers, and allowed adjustments during application. Our method offers a practical alternative to conventional glue or tape mounts, enabling longer device retention, optimal solar charging, and improved data recovery without resorting to permanent attachment methods such as harnesses. It is particularly well suited for short-term tracking applications over a few weeks to months, such as studying foraging behavior, molt timing, or seasonal movements. Overall, the clamp-based attachment system offers a practical and reliable method for short-term seabird tracking, improving data quality while minimizing impact on the birds.

• Critchley, Emma Jane; Nilsson, Anna Lisa Kristina; Helberg, Morten & May, Roelof Frans (2025). Life-cycle impact assessment of offshore wind energy development on migrating bird diversity in the North Sea. Journal of Applied Ecology. ISSN 0021-8901. 62(7), s. 1597–1610. doi: 10.1111/1365-2664.70087. Fulltekst i vitenarkiv Vis sammendrag

  1.As offshore wind energy development increases, it is vital to rapidly assess the cumulative impacts to biodiversity, particularly for migratory species that could be impacted across multiple sites. Life-cycle assessments (LCAs) are a useful tool for assessing and comparing cumulative effects over a large scale and are frequently used for decision-making in industry. We have adapted the LCA methodology to assess collision, disturbance and barrier impacts of offshore wind energy developments in the North Sea on migrating birds from Norway by 2030. 2.The potentially disappeared fraction of species (PDF)—a measure of the potential loss of species richness in an area—for collision, disturbance and barrier impacts was calculated for birds on migration within migration groups, relative to wind farm energy production in GWh. Distributions were modelled based on ring recoveries from countries surrounding the North Sea Basin, using a Brownian bridge approach. 3.Wind farm developments in the North Sea were found to have the greatest impact on migrating waterbirds and soaring birds. For most groups, potential impacts from disturbance and barrier effects were higher than impacts caused by collision. Maps highlight where cumulative PDF values for combined collision, disturbance and barrier effects are expected to be highest, both by group and for all migratory species combined. 4.Synthesis and applications: Our findings stress the potential cumulative impacts to migrating birds from large-scale offshore wind energy development in the North Sea by 2030 relative to wind farm energy production. The combination of long-term bird ringing data and LCAs, which are already widely used by industry in other contexts, could be a useful tool for comparing potential impacts across proposed wind farm sites for environmental impact assessments and national strategic environmental assessments. The LCA methodology presented here could be adapted further to rapidly assess impacts of other types of energy developments on a wide range of migratory species.

• Nilsson, Anna Lisa Kristina; Molværsmyr, Sindre; Breistøl, Arild & Systad, Geir Helge Rødli (2023). Estimating mortality of small passerine birds colliding with wind turbines. Scientific Reports. 13(1). doi: 10.1038/s41598-023-46909-z. Fulltekst i vitenarkiv Vis sammendrag

  As demand for renewable energy is rising, wind power development is rapidly growing worldwide. In its wake, conficts arise over land use changes converting pristine nature into industrial power plants and its associated adverse biodiversity efects, crowned by one of the most obvious and deadly consequences: bird collisions. Most post-construction studies report low levels of avian mortality, but the majority of these studies are conducted primarily on larger birds. However, the diversity and abundance of small passerine birds are rarely refected in the carcass surveys, although they in numeric proportion to their abundances should be the most numerous. The assumption that surveys fnd all carcasses seems thus rarely fulflled and passerine mortality is likely to be grossly underestimated. We therefore designed an experiment with dummy birds to estimate mortality of small-bodied passerines and other small-bodied birds during post-construction surveys, tested in a medium-sized wind farm in western Norway. The wind farm was surveyed weekly during the migration periods by carcass survey teams using trained dogs to fnd killed birds. The dogs in the carcass surveys were more successful in locating the large than the small dummy birds (60–200 g), where they found 74% of the large dummy birds. Detecting the smaller category (5–24 g) was more demanding and the dogs only found 17% of the small dummy birds. Correcting the post-construction carcass survey outcome with the results from the experiment leads to an almost fourfold increase in estimated mortality rates, largely due to the low detection rate of the smallest category. The detection rates will naturally vary between wind farms, depending on the specifc habitat characteristics, the efciency of the carcass surveys and the search intervals. Thus, implementing a simple experiment with dummy birds to future post-construction surveys will produce more accurate estimates of the wind turbine mortality rates, and thus improve our understanding of the biodiversity efects of conforming to a more sustainable future.

• Walseng, Bjørn; Durant, Joël; Hessen, Dag Olav; Jerstad, Kurt; Nilsson, Anna & Røstad, Ole Wiggo [Vis alle 7 forfattere av denne artikkelen] (2022). Long-term annual and spatial variation of polygyny in the white-throated dipper (Cinclus cinclus). Ecology and Evolution. 12(10). doi: 10.1002/ece3.9416. Fulltekst i vitenarkiv Vis sammendrag

  Mating strategies are key components in the fitness of organisms, and notably in birds the occurrence of monogamy versus polygyny has attracted wide interest. We address this by a very comprehensive dataset (2899 breeding events spanning the years 1978–2019) of the white-throated dipper Cinclus cinclus. Though the mating system of this species has been regarded as generally monogamous, we find that 7% of all breeding events were performed by polygynous males (approximately 15% of all pairs). The fraction of polygyny has been stable over the entire study period irrespective of population size. The assumption that polygyny is most common at low population density was not supported. Surprisingly, there was no difference between polygynous and monogamous males with regard to the quality of the territories they inhabited, ranked according to their overall frequency of use. The most common age group, first-year breeders, dominated among monogamous males, while among polygynous males second-year breeders were most common, followed by third and first-year breeders. The primary females were in general older than females mated to monogamous males, also when controlled for their general frequency in the population. The majority of the two females mated to a polygynous male, bred in the vicinity of each other. The probability for a male to be involved in polygyny more than once, was significantly higher than by chance, suggesting phenotypic quality differences among males.

• Nilsson, Anna L. K.; Skaugen, Thomas; Reitan, Trond; L'Abee-Lund, Jan Henning; Gamelon, Marlène & Jerstad, Kurt [Vis alle 11 forfattere av denne artikkelen] (2020). Hydrology influences breeding time in the white-throated dipper. BMC Ecology. 20(1). doi: 10.1186/s12898-020-00338-y. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Background Earlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions in their home ranges. In riverine ecosystems, climate change is altering the flow regime, in addition to changes resulting from the increasing demand for renewable and clean hydropower. Together with increasing temperatures, this can lead to shifts in the time window available for successful breeding of birds associated with the riverine habitat. Here, we investigated specifically how the environmental conditions at the territory level influence timing of breeding in a passerine bird with an aquatic lifestyle, the white-throated dipper Cinclus cinclus . We relate daily river discharge and other important hydrological parameters, to a long-term dataset of breeding phenology (1978–2015) in a natural river system. Results Dippers bred earlier when winter river discharge and groundwater levels in the weeks prior to breeding were high, and when there was little snow in the catchment area. Breeding was also earlier at lower altitudes, although the effect dramatically declined over the period. This suggests that territories at higher altitudes had more open water in winter later in the study period, which permitted early breeding also here. Unexpectedly, the largest effect inducing earlier breeding time was territory river discharge during the winter months and not immediately prior to breeding. The territory river discharge also increased during the study period. Conclusions The observed earlier breeding can thus be interpreted as a response to climate change. Measuring environmental variation at the scale of the territory thus provides detailed information about the interactions between organisms and the abiotic environment.

• Nilsson, Anna; Slagsvold, Tore; Røstad, Ole Wiggo; Knudsen, Endre; Jerstad, Kurt & Cadahia, Luis [Vis alle 10 forfattere av denne artikkelen] (2019). Territory location and quality, together with climate, affect the timing of breeding in the white-throated dipper. Scientific Reports. 9, s. 1–11. doi: 10.1038/s41598-019-43792-5. Fulltekst i vitenarkiv Vis sammendrag

  Recent climate change has led to advanced spring phenology in many temperate regions. The phenological response to variation in the local environment, such as the habitat characteristics of the territories birds occupy, is less clear. The aim of this study is to understand how ecological conditions affect breeding time, and its consequences for reproduction, in a white-throated dipper Cinclus cinclus population in a river system in Norway during 34 years (1978–2011). Hatching date advanced almost nine days, indicating a response to higher temperatures and the advanced phenology in the area. Earlier breeding was found in warm springs and at lower altitudes. High population density facilitated earlier breeding close to the coast. Furthermore, when population density was low, breeding was early at territories that were rarely occupied, while in years with high density, breeding was early at territories that were frequently occupied. Also, when population density was low, earlier breeding occurred at territories that on average produced more offspring than other territories, while there was no difference in breeding time in high population years. Selection for early breeding was dependent on spring temperatures and high spring temperatures contributed to higher breeding success during the study period. We found that breeding phenology may have strong effects on fitness in the white-throated dipper, and thus that breeding time is an important ecological factor in a species that feeds mainly on aquatic rather than terrestrial prey.

• Gamelon, Marlène; Tufto, Jarle; Nilsson, Anna; Jerstad, Kurt; Røstad, Ole Wiggo & Stenseth, Nils Christian [Vis alle 7 forfattere av denne artikkelen] (2018). Environmental drivers of varying selective optima in a small passerine: A multivariate, multiepisodic approach. Evolution. ISSN 0014-3820. 72(11), s. 2325–2342. doi: 10.1111/evo.13610. Fulltekst i vitenarkiv Vis sammendrag

  In changing environments, phenotypic traits are shaped by numerous agents of selection. The optimal phenotypic value maximizing the fitness of an individual thus varies through time and space with various environmental covariates. Selection may differ between different life‐cycle stages and act on correlated traits inducing changes in the distribution of several traits simultaneously. Despite increasing interests in environmental sensitivity of phenotypic selection, estimating varying selective optima on various traits throughout the life cycle, while considering (a)biotic factors as potential selective agents has remained challenging. Here, we provide a statistical model to measure varying selective optima from longitudinal data. We apply our approach to analyze environmental sensitivity of phenotypic selection on egg‐laying date and clutch size throughout the life cycle of a white‐throated dipper population. We show the presence of a joint optimal phenotype that varies over the 35‐year period, being dependent on altitude and temperature. We also find that optimal laying date is density‐dependent, with high population density favoring earlier laying dates. By providing a flexible approach, widely applicable to free‐ranging populations for which long‐term data on individual phenotypes, fitness, and environmental factors are available, our study improves the understanding of phenotypic selection in varying environments.

• Cadahia, Luis; Labra, Antonieta; Knudsen, Endre; Nilsson, Anna; Lampe, Helene M. & Slagsvold, Tore [Vis alle 7 forfattere av denne artikkelen] (2017). Advancement of spring arrival in a long‑term study of a passerine bird: sex, age and environmental effects. Oecologia. ISSN 0029-8549. 184(4), s. 917–929. doi: 10.1007/s00442-017-3922-4. Fulltekst i vitenarkiv Vis sammendrag

  In migratory birds, mistimed arrival might have negative consequences for individual fitness, causing population declines. This may happen if arrival time is not synchronized with breeding time, especially when earlier springs favour earlier reproduction. We studied spring arrival time to the breeding areas in a pied flycatcher Ficedula hypoleuca population in southern Norway during a 30-year period (1985–2014). We investigated trends in arrival both for the entire population and for different population fractions (e.g. early vs. late arrivals). We also studied sex and age class differences, along with repeatability of arrival. Finally, we explored how arrival is influenced by environmental conditions at the areas birds use throughout the year, using mixed-effects models and quantile regressions with individual-based data. Spring arrival advanced over five days, at a similar rate through the entire population. Males and adult birds arrived earlier than females and yearlings. Arrival was significantly repeatable for males and females. Birds arrived earlier in years with high temperature and rainfall at the breeding grounds, and low NDVI both on the Iberian Peninsula and in central Europe. Later fractions of the population showed a steeper response to these environmental variables. This intra-population heterogeneity in the responses to the environment probably stems from a combination between the different selection pressures individuals are subject to and their age-related experience. Our results highlight the importance of studying how migration phenology is affected by the environment not only on the breeding grounds but also on the other areas birds use throughout the year.

• Gamelon, Marlène; Grøtan, Vidar; Nilsson, Anna L. K.; Engen, Steinar; Hurrell, James W. & Jerstad, Kurt [Vis alle 12 forfattere av denne artikkelen] (2017). Interactions between demography and environmental effects are important determinants of population dynamics. Science Advances. 3(2). doi: 10.1126/sciadv.1602298. Fulltekst i vitenarkiv Vis sammendrag

  Climate change will affect the population dynamics of many species, yet the consequences for the long-term persistence of populations are poorly understood. A major reason for this is that density-dependent feedback effects caused by fluctuations in population size are considered independent of stochastic variation in the environment. We show that an interplay between winter temperature and population density can influence the persistence of a small passerine population under global warming. Although warmer winters favor an increased mean population size, density-dependent feedback can cause the local population to be less buffered against occasional poor environmental conditions (cold winters). This shows that it is essential to go beyond the population size and explore climate effects on the full dynamics to elaborate targeted management actions.

• Nilsson, Anna; Nilsson, Jan-Åke & Mettke-Hofmann, Claudia (2016). Energy reserves, information need and a pinch of personality determine decision-making on route in partially migratory blue tits. PLOS ONE. 11(10), s. 1–18. doi: 10.1371/journal.pone.0163213. Fulltekst i vitenarkiv Vis sammendrag

  In facultative partial migrants some individuals in a population are migratory and others are resident and individuals decide each year anew which strategy to choose. While the proportion of birds migrating is in part determined by environmental conditions and competitive abilities, the timing of individual departure and behaviours on route are little understood. Individuals encounter different environmental conditions when migrating earlier or later. Based on cost/ benefit considerations we tested whether behaviours on route were affected by time constraints, personality and/or age in a partially migrating population of Blue tits (Cyanistes caeruleus). We captured female Blue tits on migration at the Southern tip of Sweden during early, peak and late migration and measured latency to feed in an unfamiliar environment, exploration of a novel object and hesitation to feed beside a novel object (neophobia). Lean birds and birds with long wings started feeding earlier when released into the cage indicating that foraging decisions were mainly determined by energetic needs (lean and large birds). However, juveniles commenced feeding later with progression of the migratory season in concordance with predictions about personality effects. Furthermore, lean birds started to explore earlier than birds with larger fat reserves again indicating an effect of maintaining threshold energy reserves. Moreover, late migrating juveniles, started to explore earlier than early migrating juveniles possibly due to time constraints to find high-quality foraging patches or a suitable winter home. Finally, neophobia did not change over the migratory season indicating that this behaviour is not compromised by time constraints. The results overall indicate that decisions on route are mainly governed by energetic requirements and current needs to learn about the environment and only to a small extent by differences in personality.

• Nilsson, Anna; Nilsson, JA & Alerstam, Thomas (2011). Basal metabolic rate and energetic cost of thermoregulation among migratory and resident blue tits. Oikos. ISSN 0030-1299. 120, s. 1784–1789. doi: 10.1111/j.1600-0706.2011.19440.x. Fulltekst i vitenarkiv
• Knudsen, Endre; Linden, Andreas; Both, Christiaan; Jonzén, Niclas; Pulido, Francisco & Saino, Nicola [Vis alle 27 forfattere av denne artikkelen] (2011). Challenging claims in the study of migratory birds and climate change. Biological Reviews. ISSN 1464-7931. 86, s. 928–946. doi: 10.1111/j.1469-185X.2011.00179.x. Fulltekst i vitenarkiv
• Nilsson, Anna; Knudsen, Endre; Jerstad, Kurt; Røstad, Ole Wiggo; Walseng, Bjørn & Slagsvold, Tore [Vis alle 7 forfattere av denne artikkelen] (2011). Climate effects on population fluctuations of the white-throated dipper Cinclus cinclus. Journal of Animal Ecology. ISSN 0021-8790. 80(1), s. 235–243. doi: 10.1111/j.1365-2656.2010.01755.x. Fulltekst i vitenarkiv
• Nilsson, Anna; Stige, Leif Christian; Jerstad, Kurt; Røstad, Ole Wiggo; Slagsvold, Tore & Knudsen, Endre [Vis alle 8 forfattere av denne artikkelen] (2011). To make the most of what we have: extracting phenological data from nestling measurements. International journal of biometeorology. ISSN 0020-7128. 55, s. 797–804. doi: 10.1007/s00484-011-0461-2. Fulltekst i vitenarkiv
• Nilsson, Anna; Nilsson, Jan-Åke; Alerstam, Thomas & Bäckman, Johan (2010). Migratory and resident blue tits Cyanistes caeruleus differ in their reaction to a novel object. Die Naturwissenschaften. ISSN 0028-1042. 97(11), s. 981–985. doi: 10.1007/s00114-010-0714-7. Fulltekst i vitenarkiv
• Nilsson, Anna & Sandell, Maria I (2009). Stress hormone dynamics: an adaptation to migration? Biology Letters. ISSN 1744-9561. 5, s. 480–483. doi: 10.1098/rsbl.2009.0193. Fulltekst i vitenarkiv
• Nilsson, Anna; Alerstam, Thomas & Nilsson, Jan-Åke (2008). Diffuse, short and slow migration among blue tits. Journal of Ornithology = Journal fur Ornithologie. ISSN 0021-8375. 149, s. 365–373. doi: 10.1007/s10336-008-0280-3. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• May, Roelof Frans; Anker-Nilssen, Tycho; Ballesteros, Manuel; Bråthen, Vegard Sandøy; Buckingham, Lila & Bærum, Kim Magnus [Vis alle 25 forfattere av denne artikkelen] (2026). Offshoreaktivitetog sjøfugl. Fulltekst i vitenarkiv
• Bargmann, Tessa; Buckingham, Lila; Christensen-Dalsgaard, Signe; Critchley, Emma Jane; Daunt, Francis & Dehnhard, Nina [Vis alle 19 forfattere av denne artikkelen] (2025). Developing a tool to assess the cumulative impacts of marine industry and climate on seabirds. Fulltekst i vitenarkiv
• Cordes, Line; Critchley, Emma Jane; Hamre, Øyvind; Nilsson, Anna Lisa Kristina & May, Roelof Frans (2025). Multi-season monitoring of bird migration at coastal locations in Norway. Fulltekst i vitenarkiv
• Reiertsen, Tone Kristin; Tarroux, Arnaud; Fauchald, Per; May, Roelof Frans; Nilsson, Anna Lisa Kristina & Critchley, Emma Jane [Vis alle 12 forfattere av denne artikkelen] (2025). MARCIS - marine spatial planning and cumulative impact of blue growth on seabirds. Fulltekst i vitenarkiv
• Critchley, Emma Jane; Nilsson, Anna Lisa Kristina & May, Roelof Frans (2024). Life-cycle impact assessment of offshore wind energy development on migrating bird diversity in the North Sea. Fulltekst i vitenarkiv
• Critchley, Emma Jane; Nilsson, Anna Lisa Kristina; Helberg, Morten & May, Roelof Frans (2024). Life-cycle impact assessment of offshore wind energy development on migrating seabird diversity in the North Sea. Fulltekst i vitenarkiv
• Critchley, Emma Jane; Nilsson, Anna Lisa Kristina & May, Roelof Frans (2023). Life-cycle impact assessment of offshore wind energy development on migrating bird diversity in the North Sea. Fulltekst i vitenarkiv
• May, Roelof Frans; Nilsson, Anna; Szymanski, Anne-Laure & Murvoll, Kari-Mette (2022). WP2 - Novel marine stressors and receptors. Fulltekst i vitenarkiv
• Nilsson, Anna (2022). Havvind og fugl - presentasjon av MARCIS og kunnskapsstatus. Fulltekst i vitenarkiv
• Nilsson, Anna & May, Roelof Frans (2022). Offshore wind power impacts on birds at Hywind Tampen. Fulltekst i vitenarkiv
• May, Roelof Frans; Nilsson, Anna; Critchley, Emma Jane; Szymanski, Anne-Laure & Murvoll, Kari-Mette (2022). WP2 - Novel marine stressors and receptors. Fulltekst i vitenarkiv
• Nilsson, Anna L.K.; Reitan, Trond; Skaugen, Thomas; L'Abee-Lund, Jan Henning; Gamelon, Marlène & Jerstad, Kurt [Vis alle 11 forfattere av denne artikkelen] (2020). Location Is Everything, but Climate Gets a Share: Analyzing Small-Scale Environmental Influences on Breeding Success in the White-Throated Dipper. Frontiers in Ecology and Evolution. doi: 10.3389/fevo.2020.542846. Fulltekst i vitenarkiv Vis sammendrag

  Ecological and evolutionary effects of environmental variation on wild populations are of particular interest in a changing world. Large-scale environmental indices are classically used as environmental explanatory variables to study climate change effects on wild populations. However, these measures neglect the fact that individuals are affected by the local conditions in their home ranges. Freshwater ecosystems are particularly sensitive to climate change induced alterations in precipitation and discharge affecting lower trophic level prey and cascading up the food chain to impact keystone species. Here, we study how small-scale environmental variation at the level of each territory affects fitness-related traits and in particular reproductive success in the white-throated dipper Cinclus cinclus, a bird dependent on aquatic prey. We take advantage of a long-term study of breeding dippers in a natural river system in Norway (1978–2015). We relate daily river discharge and other important hydrological and territory location variables to clutch and brood size simultaneously, while accounting for male and female age, polygyny, and population density. We also address uncertainty in estimates of both clutch and brood size when modeling reproductive success. The most influential variable overall was the altitudinal gradient, where birds breeding at higher altitudes laid fewer eggs and fledged fewer young. Clutch size decreased with increased population density and high temperatures, while it was positively affected by female age. Brood size varied greatly among territories, where some territories had consistently larger broods than others. Increased minimum and maximum temperatures, river discharge above 10 l/s and increased variability in snow depth had a positive effect on brood size, whereas polygyny had a negative effect. In conclusion, territory-specific variables explained a large amount of the variation in the reproductive output in the dipper, emphasizing the importance of the local habitat, and not only climatic variation, in a keystone species in freshwater ecosystems.

• Walseng, Bjørn; Jerstad, Kurt; Nilsson, Anna L.K. & Røstad, Ole Wiggo (2017). Har kalking resultert i en bedre hekkesuksess hos fossekallen i Lyngdalsvassdraget 1978-2011? pH-status : forum for sur nedbør og kalking. ISSN 0808-4882. 23(4), s. 4–6. Fulltekst i vitenarkiv
• Nilsson, Anna; L'Abee-Lund, Jan Henning; Vøllestad, Leif Asbjørn; Jerstad, Kurt; Larsen, Bjørn Mejdell & Røstad, Ole Wiggo [Vis alle 10 forfattere av denne artikkelen] (2017). The potential influence of Atlantic salmon Salmo salar and brown trout Salmo trutta on density and breeding of the white-throated dipper Cinclus cinclus. Ecology and Evolution. doi: 10.1002/ece3.3958. Fulltekst i vitenarkiv Vis sammendrag

  Interactions between birds and fish are often overlooked in aquatic ecosystems. We studied the influence of Atlantic salmon and brown trout on the breeding population size and reproductive output of the white-throated dipper in a Norwegian river. Acidic precipitation led to the extinction of salmon, but salmon recolonized after liming was initiated in 1991. We compared the dipper population size and reproductive output before (1978–1992) and after (1993–2014) salmon recolonization. Despite a rapid and substantial increase in juvenile salmon, the breeding dipper population size and reproductive output were not influenced by juvenile salmon, trout, or total salmonid density. This might be due to different feeding strategies in salmonids and dippers, where salmonids are mainly feeding on drift, while the dipper is a benthic feeder. The correlation between the size of the dipper population upstream and downstream of a salmonid migratory barrier was similar before and after recolonization, indicating that the downstream territories were not less attractive after the recolonization of salmon. Upstream dipper breeding success rates declined before the recolonization event and increased after, indicating improved water quality due to liming, and increasing invertebrate prey abundances and biodiversity. Surprisingly, upstream the migratory barrier, juvenile trout had a weak positive effect on the dipper population size, indicating that dippers may prey upon small trout. It is possible that wider downstream reaches might have higher abundances of alternative food, rending juvenile trout unimportant as prey. Abiotic factors such as winter temperatures and acidic precipitation with subsequent liming, potentially mediated by prey abundance, seem to play the most important role in the life history of the dipper.

• Skaugen, Thomas; Peerebom, Ivar Olaf & Nilsson, Anna (2015). Use of a parsimonious rainfall-run-off model for predicting hydrological response in ungauged basins. Hydrological Processes. ISSN 0885-6087. 29(8), s. 1999–2013. doi: 10.1002/hyp.10315. Fulltekst i vitenarkiv Vis sammendrag

  A new parameter parsimonious rainfall–run-off model, the Distance Distribution Dynamics (DDD) model, is used to simulate hydrological time series at ungauged sites in the Lygne basin in Norway. The model parameters were estimated as functions of catchment characteristics determined by geographical information system. The multiple regression equations relating catchment characteristics and model parameters were trained from 84 calibrated catchments located all over Norway, and all model parameters showed significant correlations with catchment characteristics. The significant correlation coefficients (with p-value < 0.05) ranged from 0.22 to 0.55. The suitability of DDD for predictions in ungauged basins was tested for 17 catchments not used to estimate the multiple regression equations. For ten of the 17 catchments, deviations in Nash–Sutcliffe efficiency (NSE) criteria between the calibrated and regionalised model were less than 0.1, and for two calibrated catchments within the Lygne basin, the deviations were less than 0.08. The median NSE for the regionalized DDD for the 17 catchments for two time series was 0.66 and 0.72. Deviations in NSE between calibrated and regionalised models are well explained by the deviations between calibrated and regressed parameters describing spatial snow distribution and snowmelt respectively. The quality of the simulated run-off series for the ungauged sites in the Lygne basin was assessed by comparing flow indices describing high, medium and low flow estimated from observed run-off at the 17 catchments and for the simulated run-off series. The indices estimated for the simulated series were generally well within the ranges defined by the 17 observed series.

• Nilsson, Anna (2012). Making use of extracted phenology data: analyzing 35 years of dipper breeding phenology. Fulltekst i vitenarkiv
• Nilsson, Anna (2012). Stochastic demography in fluctuating environments: theory and empirical patterns. Fulltekst i vitenarkiv
• Nilsson, Anna (2010). To make the most of what we have – extracting phenology data from nestling measurements. Fulltekst i vitenarkiv Vis sammendrag

  Among the most well documented examples of climate change is the change in timing of annual events. Changes in phenology have been particularly prominent among birds. To study the ecological and evolutionary effects of climate change, scientists need access to data that has been collected over long time periods. Many long-term studies on breeding birds include detailed information about individually marked parents and offspring, but does not include information on phenology, as this often requires an even larger field effort. We demonstrate how a study of repeated standard measurements of nestlings can be used for modeling nestling growth, and how this statistical model can be used to estimate timing of breeding also for birds with sparser data. Using data from our model system of a population of white-throated dippers Cinclus cinclus in southernmost Norway, studied from 1978 until present, we also demonstrate how the extracted estimates of timing of breeding can be used for studying the ecological effects of climate change.

• Nilsson, Anna (2010). Causes and consequences of partial migration – using ringing recovery data for linking movement strategies with life-histories. Fulltekst i vitenarkiv Vis sammendrag

  In studies of partial migration, the question of interest is often approached in one of two ways. We either study the migratory process, where we typically have little or no knowledge of the breeding performance, or we study the breeding ecology and do not know exactly which individuals are migrating, dispersing or not surviving through the non-breeding season. This is due to our inability to track individuals close enough to follow them outside our window of study. With this study, we attempt to connect these two unfortunately disconnected processes of migration and breeding and thereby translate individual movement strategies into life-history ecology. Since 1973, we have studied a dipper Cinclus cinclus population in southernmost Norway. The dipper occupies a very specialized niche compared to other passerine partial migrants. It is an obligate specialist feeding on aquatic insects submerged in running fresh water. From the start of the study, individuals have been recovered abroad during winter, while others have been wintering in the study area. As all individuals are individually marked and the breeding ecology particularly well known in this system, we are able to relate movement strategies to breeding performance and survival. Ultimately, this enables us to place individual movement trajectories into a life-history context.

• Nilsson, Anna (2009). Bird migration and climate change. Fulltekst i vitenarkiv
• Nilsson, Anna (2008). Flyttfåglar och klimatförändringar. Fulltekst i vitenarkiv
• Nilsson, Anna Lisa Kristina; Breistøl, Arild; Helberg, Morten & Molværsmyr, Sindre (2025). Fungerer vern og ferdselsrestriksjoner for sjøfuglene? Bestandsutvikling, hekkesuksess og rekruttering hos gråmåke i og utenfor sjøfuglreservatene. Norsk institutt for naturforskning (NINA). ISSN 9788242655141. Fulltekst i vitenarkiv Vis sammendrag

  Nilsson, A.L.K., Breistøl, A., Helberg, M. & Molværsmyr, S. 2025. Fungerer vern og ferdselsrestriksjoner for sjøfuglene? Bestandsutvikling, hekkesuksess og rekruttering hos gråmåke i og utenfor sjøfuglreservatene. NINA Rapport 2687. Norsk institutt for naturforskning. Nedgangene i sjøfuglbestandene er nå så omfattende at en tilsynelatende vanlig art som gråmåke Larus argentatus er blitt tatt med på den norske rødlisten over truede arter. Av alle årsaker som bidrar til bestandsnedgangene hos norske og internasjonale sjøfuglbestander er menneskelig forstyrrelse i hekketiden en årsak som ofte adresseres av forvaltningen med ferdselsrestriksjoner på hekkeplassene. Siden det er få, om noen, studier som kan påvise positiv effekt av dette tiltaket, er det stor usikkerhet om disse forvaltningstiltakene har den ønskede effekten. I dette arbeidet undersøkte vi effekten av ferdselsrestriksjonene gjennom å studere forskjell i utviklingen i kolonistørrelse og ungeproduksjon mellom vernede og ikke-vernede sjøfuglkolonier. I tillegg studerte vi rekrutteringen til og fra disse koloniene i et skjærgårdsområde på Sørlandet med mange vernede og ikke-vernede kolonier. Vi brukte tidsserier på kolonistørrelse og ungeproduksjon fra BirdLife Mandal og SEAPOP, og data fra fargeringmerkingsbasen ringmerking.no for rekrutteringsanalysene. Kolonier med ferdselsrestriksjoner var større og produserte flere unger per par enn kolonier uten. De lokale gråmåkebestandene minket kraftig, med nesten 30 par per tiår, og kolonier uten ferdselsrestriksjoner minket raskere enn vernede kolonier. Ungeproduksjonen sank betraktelig over tid i studieperioden, men ingen statistiske forskjeller i nedgang over tid mellom vernede og ikke-vernede kolonier ble registrert. Unger som var store nok til å få fargering, rekrutterte i likt omfang fra verne- og ikke-verneområde. Imidlertid rekrutterte ungene helst inn i kolonier med samme vernestatus som der de selv ble klekket. Siden gråmåken dermed viser en form for stedtrohet, er forholdene på hekkeplassene svært viktige. Som forvaltningstiltak kan ferdselsrestriksjoner på øyer med hekkende sjøfugl til en viss grad bidra til at fuglene kan hekke uforstyrret, noe som potensielt kan minske hastigheten på bestandsnedgangene. Dette tiltaket er imidlertid ikke nok til å forbedre bestandstrendene for norske gråmåker.

• Reiertsen, Tone Kristin; Breistøl, Arild; Hagestad, Sine; Helberg, Morten; Jacobsen, Karl-Otto & Molværsmyr, Sindre [Vis alle 7 forfattere av denne artikkelen] (2025). Sameksistens med urbane måker og terner – kunnskapsbaserte råd om tiltak og tilrettelegging. Norsk institutt for naturforskning (NINA). ISSN 9788242653956. Fulltekst i vitenarkiv
• Stokke, Bård Gunnar; Hamre, Øyvind; May, Roelof Frans; Molværsmyr, Sindre; Nilsson, Anna Lisa Kristina & Pavon-Jordan, Diego (2024). 420 kV Skaidi-Lebesby – radar-undersøkelser av flygeaktivitet hos dverggås og tundrasædgås ved Stabbursneset, Porsanger. Norsk institutt for naturforskning (NINA). ISSN 9788242651341. Fulltekst i vitenarkiv Vis sammendrag

  I 2022 og 2023 ble en fugleradar benyttet til å undersøke flygeaktivitet hos dverggjess (Anser erythropus) og tundrasædgjess (Anser serrirostris) ved Stabbursneset, Porsanger i Finnmark. Dverggjess som fløy vestover fra det viktige rasteområdet på Valdakmyra fulgte i hovedsak én bestemt øst-vest led opp langs en bekkedal i den sørlige delen av området. Tundrasædgjessene benyttet en større del av området og hadde både en øst-vest og sør-nord flygeretning. Gjess som returnerte tilbake østover til Valdakmyra fulgte som regel ingen bestemt led, og ankom i relativt store høyder før landing. Statnett SF planlegger oppføring av en 420 kV kraftledning i området vest for Valdakmyra i nord-sør retning. Det foreligger planer for tre alternative traséer; en som ligger rett vest for Valdakmyra (det «østlige» alternativet), en som følger traséen til eksisterende 132 kV kraftledning (det «midtre» alternativet), og en som tenkes plassert lenger vest (det «vestlige» alternativet). Radardata samt visuelle observasjoner avdekket at både dverggjess og tundrasædgjess i utstrakt grad krysset de tre traséene på vei til og fra Valdakmyra. Det «østlige» alternativet anses svært uheldig siden en rekke registeringer avdekket flygehøyder som innebærer stor kollisjonsrisiko. Begge de to andre alternativene synes mer relevant med hensyn til å redusere potensiell kollisjonsrisiko med kraftledningene for begge arter. Grunnen til dette er at gjess som lettet fra Valdakmyra vant høyde etter hvert som de beveget seg vestover. I de fleste tilfellene passerte de dermed i sikker høyde over disse alternativene. Tilsvarende tapte gjess som kom vestfra høyde etter hvert som de nærmet seg Valdakmyra. Det er viktig å bemerke at vi på bakgrunn av to år med radardata i vårperioden ikke kan utelukke at andre flygeleder til og fra Valdakmyra kan være viktige i enkelte år eller i løpet av høsten etter hekkesesongen. For eksempel vil andre værforhold enn de som var rådende i 2022 og 2023 kunne påvirke hva som er den mest energieffektive flygeleden for gjess og andre fuglearter i området. I tillegg må det bemerkes at radaren ikke fanget opp lave flygehøyder i deler av området, spesielt ved det «vestlige» alternativet. Dersom det skal oppføres nye kraftledninger bør det sterkt vurderes å merke ledningene med fugleavvisere langs kritiske deler av traséen for å redusere kollisjonsrisiko, samt søke systematisk etter kollisjonsofre for å danne seg et bilde av omfanget av eventuelle kollisjoner.

• Cordes, Line; Hamre, Øyvind; Nilsson, Anna Lisa Kristina; López, Aïda; Portela, Diogo & Røer, Jan Erik [Vis alle 7 forfattere av denne artikkelen] (2024). Bird migration at Lista and Utsira 2023. Migration for Development. Norwegian Institute of Nature Research (NINA). ISSN 9788242652966. Fulltekst i vitenarkiv Vis sammendrag

  The Migration for Development project is jointly funded by industry partners and implemented to complement and support the VisAviS collaborative research project funded by the Research Council of Norway. As part of the work, two avian radars were deployed at coastal locations in Norway to record seasonal bird migrations. Here, we present an investigation of the avian radar data collected at Lista (Farsund municipality) during the spring and autumn and at Utsira during the autumn of 2023. Firstly, using radar tracks annotated by an observer, we show case issues with how the radar classifies bird tracks (small, medium, large and flock). We used the data from annotated tracks to provide improved categories of radar tracks. Secondly, using all tracks collected by the radar, we filtered these based on likely migration flight characteristics, and present temporal and spatial patterns of probable migration tracks. The length and definition of the migration season varied by location. Migration peaks most consistently occurred from late afternoon through the evening. There were significant site- and season-specific differences in flight height and the proportion of birds in the rotor swept zone. At Lista a significant proportion of birds flew within the clearance zone between the sea surface and the rotor swept zone. We recommend including the proportion of birds flying in this narrow band (20m) in considerations of impacts of wind energy developments. Birds tended to migrate with a tail or cross-tail wind. Lastly, there were site-specific differences in size groups detected at Lista and Utsira, with Utsira predominantly detecting birds in the intermediate category and just a few large flocks, but no small birds. At Lista, all categories were detected by the radar.

• Nilsson, Anna Lisa Kristina; Molværsmyr, Sindre; Breistøl, Arild; Hamre, Øyvind & Systad, Geir Helge Rødli (2023). Effekter på fugletrekket over Guleslettene. Etterundersøkelser ved Guleslettene vindkraftverk. Norsk institutt for naturforskning (NINA). ISSN 9788242650245. Fulltekst i vitenarkiv Vis sammendrag

  Etterundersøkelsene bekreftet funnene fra forundersøkelsene av et omfattende fugletrekk over Guleslettene som årlig passerer vindkraftverket vår (mars-mai) og høst (juli-oktober). I møte med vindkraftverket kunne vi vise at fuglene trakk høyere og at flere gjorde unnvikelsesmanøvrer enn før det ble bygget. Det ble funnet totalt 105 drepte fugler de to årene det ble søkt etter kollisjonsofre, 31 om våren og 74 om høsten. Hver turbin drepte mellom null og fem fugler per trekksesong; Hoveddelen av fuglene som ble drept av turbinene i Guleslettene vindkraftverk var spurvefugl, noe som er i tråd med forventningene siden spurvefugl utgjør mesteparten av de forbitrekkende fuglene (visuelle observasjoner og songmeterdata). Kollisjonsfunnene inkluderer fem individer av rødlistede arter (fire heilo Pluvialis apricaria og en stær Sturnus vulgaris). Spurvefugl er den mest tallrike gruppen fugler, men de er små og kan være utfordrende å finne i søkene etter kollisjonsdrepte fugler. Søkene etter kollisjonsofre ble gjort av hunder trent for formålet. Siden hundene på Guleslettene var dyktige til å finne mindre fugler selv i utfordrende værforhold, designet vi et eksperiment med utlegging av døde fugler for å estimere hvor stor den faktiske turbindødeligheten var. Større spurvefugler som stær og trost var klart lettere å finne (74 %) enn mindre spurvefugler som rødstrupe og heipiplerke (17 %), selv for godt trente hunder. Basert på dette estimerte vi at 400 fugler samlet sett ble drept under etterundersøkelsene 2021-2022 (341 små spurvefugler, 45 større småfugler samt 14 store fugler). Dette tilsvarer 0,77 drepte fugler per turbin og undersøkelsesmåned, eller 0,62 drepte fugler per produsert GWh. Det understrekes at dette er et estimat for vår- og høstsesongen, og inkluderer ikke sommer- eller vintersesongen. En sammenligning av radardata fra vårsesongene i for- og etterundersøkelsene viste at fuglene som passerte Guleslettene om dagen trakk høyere etter utbygging enn før turbinene var på plass. Vi kunne også vise at flere fugler endret trekkretning i møte med turbinene i vindkraftverket. Dette tyder på at fuglene aktivt unnviker å fly gjennom vindkraftverket. Natt-trekket over Guleslettene gikk på samme høyde både før- og etter utbygging, noe som indikerer at nattrek-kende fugler kanskje ikke har samme muligheter til å oppdage hinder foran dem i luftlagene, og derfor er mer utsatt for kollisjon enn dagtrekkende arter. Siden trekkaktiviteten fortsatt var høy etter utbyggingen, og det faktisk ble registrert flere radarspor i etter- enn forundersøkelsen, trek-ker fuglene sannsynligvis gjennom området i like stor grad som før vindkraftverket ble bygget. Trekket foregår hovedsakelig om natten. Om høsten trakk også større finkeflokker gjennom området på formiddagstimene. Sammenligning av data fra songmetere (lyttebokser) og radar viste en større aktivitet om dagen av lydytrende fugler enn om natten, noe som indikerer at den store massen av nattrekkende fugler lager lite lyd, eller at de flyr for høyt for at lydene registreres av songmeterne. Deteksjonene fra radar og songmetere samvarierte i svært liten grad, og songmeterdata alene er dermed ikke egnet for å kvantifisere trekkaktivitet. Songmeteropptak, sammen med visuelle observasjoner, bidro derimot med artsbestemmelse av fuglene som trakk forbi.

• Layton-Matthews, Kate; Buckingham, Lila; Critchley, Emma Jane; Nilsson, Anna Lisa Kristina; Ollus, Victoria Marja Sofia & Ballesteros, Manuel [Vis alle 16 forfattere av denne artikkelen] (2023). Development of a Cumulative Impact Assessment tool for birds in Norwegian Offshore Waters: Trollvind OWF as a case study. Norsk institutt for naturforskning (NINA). ISSN 9788242650931. Fulltekst i vitenarkiv Vis sammendrag

  - North Sea - Seabirds - Migratory birds - Impact assessment - Offshore wind - Climate change

• Cordes, Line; Nilsson, Anna Lisa Kristina; Hamre, Øyvind & May, Roelof Frans (2023). Preliminary exploration of radar data from Lista covering the spring bird migration (2023). Migration for Development. Norsk institutt for naturforskning (NINA). ISSN 9788242652119. Fulltekst i vitenarkiv Vis sammendrag

  The Migration for Development project is jointly funded by industry partners and put in place to complement and support the VisAviS collaborative research project funded by the Research Council of Norway. As part of the work, two avian radars were deployed at coastal locations in Norway to record seasonal bird migrations. Here, we present a preliminary investigation of the avian radar data collected at Lista (Farsund municipality) during spring 2023. Firstly, using radar tracks annotated by an observer, we showcase issues with how the radar classifies bird tracks (small, medium, large and flock). The radar tends to underestimate the size of birds and thereby provide an inflated estimate of numbers of small birds. We used the data from annotated tracks to provide improved categories of radar tracks and to explore flight characteristics of known bird species. Secondly, using all tracks collected by the radar, we filtered these based on likely migration flight characteristics, and present temporal and spatial patterns of probable migration tracks. There was temporal variation in the number of tracks recorded per day by the radar. Within a day, larger numbers of small birds were typically detected during the evening or night. There was a large proportion of low flying birds in or below the rotor swept zone vulnerable to collision with turbines. The radar detection range varied by category from 5 km for small birds to 13.6 km for larger flocks of large birds. However, given the issues with the way the radar classifies tracks, this report only presents a preliminary view of the avian radar data collected, and we discuss the next steps to be taken and plans for actual analysis of these data to be presented in the following report.

• Nilsson, Anna Lisa Kristina; Skytterholm, Andrea Neverdal; Frassinelli, Francesco; Jaatun, Martin Gilje; Vang, Roald & Pavon-Jordan, Diego [Vis alle 8 forfattere av denne artikkelen] (2023). Forskningskart på vindkraft – en pilotstudie. Vindkraftens påvirkninger på fugl og cybersikkerhet i drift av vindkraft. Norsk institutt for naturforskning (NINA). ISSN 9788242650016. Fulltekst i vitenarkiv Vis sammendrag

  - forskningskart, kunnskapsoversikt - vindkraft - fugl - landbasert vindkraft - havvind - cybersikkerhet

• Zinke, Peggy & Nilsson, Anna (2021). Plan for vannforvaltning og forslag til tiltak i Nesheimsumpen naturreservat - Trinn 1 Med vekt på naturmangfoldet, karbonlagring i myr og flomdemping. Sciencemonastery. Fulltekst i vitenarkiv
• Holtskog, Thorstein; Dervo, Børre Kind; Mjelde, Marit; Zinke, Peggy; Nygård, Magnus & Elvigen, Stine Wiger [Vis alle 8 forfattere av denne artikkelen] (2020). Restaureringsplan for Gjølsjøen - 2020. Dokkadeltaet Våtmarkssenter Rapport 2020-13. Fulltekst i vitenarkiv
• Molværsmyr, Sindre; Ergon, Torbjørn; Nilsson, Anna & Helberg, Morten (2019). Colony formation and breeding success in the rapidly declining Black-headed Gull. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Black-headed Gulls are in rapid decline in Norway and is categorized as VU (Vulnerable) on the national Red List. The Norwegian population has decreased from 30 000 pairs around 1990 to just 7000 pairs in 2011. In the study area, the inner Oslo Fjord, the total breeding population counted about 3000 pairs in 2018. This study aims to explain variations in nest and chick survival both within and between colonies, with respect to date of individual nest settlement or colonies establishment, as well as stress elements and colony defence. Multiple colonies were monitored with a combination of nest cameras and drone footage throughout the breeding cycle. From this, data regarding formation, as well as nest and chick survival, were analysed. Of 3050 Black-headed Gull nests monitored in this thesis, one in five produced chicks. Pairs settling early in the breeding season had a much higher nest survival probability than those that settled later. This was true both within and between colonies. Larger colonies had higher nest survival than smaller colonies. The most observable reason for nest and colony failures were predation from Crows, large Gulls, Red Foxes and Badgers. Colonies that failed completely were likely to have a weaker colony defence due to behavioural changes, which made the colony more accessible for predators. Low food availability and a combination of other stress factors are presumed to have made many pairs in the colonies invest less energy in current reproduction and rather focus on own survival and future breeding attempts. From a population perspective, this strategy is sustainable for a few years, but if breeding seasons with low reproduction success are too frequent, the species decline will continue, possible until extinction in Norway.

• Jerstad, Kurt; Walseng, Bjørn; Nilsson, Anna & Røstad, Ole Wiggo (2012). Fossekallen i Lyngdalsvassdraget 1978-2011. Har kalking resultert i en bedre hekkesuksess? Norsk institutt for naturforskning (NINA). ISSN 9788242624031. Fulltekst i vitenarkiv Vis sammendrag

  Fossekallbestanden har variert fra 20 til 117 hekkende par i perioden 1978-2011. Til sammen er det ved 158 hekkelokaliteter utført 4709 årssjekker. Middeltemperaturen under vinteren sammen med nedbøren, tidspunktet for islegging på systemets største innsjø, samt NAO-indeks gir de viktigste bidragene til å forklare svingningene i fossekallbestanden. De mest brukte hekkelokalitetene har både størst andel vellykkede hekkeforsøk og produserer flest unger per kull. Det er en direkte sammenheng mellom hekkesuksess og følgende fire variabler: bestandstetthet, høyde over havet, skjul av reiret og kalking. Andel vellykkede hekkeforsøk går ned i år med høy hekkebestand og avtar med høyde over havet. Ungekullstørrelsen viser også at det i gjennomsnitt blir produsert flere unger per kull i de lavereliggende områder. En bedre hekkesuksess i lavereliggende områder er tilfelle også når kalkede lokaliteter utelukkes. Andel vellykkede hekkeforsøk var større når reirene lå skjult enn når de lå åpent eller synlig. Dette resulterte i at reir bak foss og inne i bruer, som oftest lå skjult, gjorde det bra. Et unntak var ”på stein i elva/fossen” der 78,8 % var vellykket til tross for at disse alltid lå åpent eller synlig. Legger vi til grunn lokaliteter som er, eller har vært berørt av kalking, har andelen vellykkede hekkeforsøk vært signifikant høyere i en kalket situasjon sammenlignet med en ukalket situasjon. Antall unger produsert pr hunn har også vært større. Etter etableringen av kalkdosereren ved Rossevatn har antall hekkende par på strekningen nedstrøms blitt redusert, noe som antakelig skyldes en endret tilgang på byttedyr.

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