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The early life movement patterns of long-lived, large raptors, such as the white-tailed eagle (Haliaeetus albicilla), remain largely unexplored. In this study, we have tracked 22 individuals of white-tailed eagles hatched in Denmark to investigate key parameters, including survival rates, causes of death, nest site fidelity, geographical distribution, and dispersal behaviors. Our analyses are based on approximately 340,000 GPS/GSM telemetry positions from the 22 individuals. We found that survival rates were lower in the first year of life, especially among females, but increased in subsequent years. The primary causes of death were wind turbine collisions and avian influenza. Movement analyses revealed that juvenile eagles frequented nest sites in August and September, with females showing earlier exploratory flights and dispersal. Both males and females spent most of their first calendar year near their nest sites. In the second calendar year, a significant proportion of their time was spent at well-known white-tailed eagle resting areas in Denmark, as well as visiting neighboring countries. Notably, one individual set a new distance record for a Danish GPS-tagged white-tailed eagle, venturing at least 1750 km away from its nest site to visit Sweden, Finland, Russia, and Norway. Our results, indicating that juvenile white-tailed eagles continue to utilize nest sites into September, suggest an extension of the recommended time period for nest protection zones provided by BirdLife Denmark (DOF). more...

Capsule: Mortality varies across capture methods but remains overall low.Aims: To investigate mortality associated with ringing operations in Denmark and the FaroeIslands, including the effects of species and capture methods.Methods: We analyzed data for mortality rates of birds arising from ringing operations in Denmarkand the Faroe Islands over a 20-year period. The data included a variety of capture methods andaltogether the reports involve 1.8 million individuals.Results: The overall mortality rate during ringing operations was 0.16%. The dominant form ofcapture, mist-netting, had a mortality rate of 0.21%, comparable to similar published studies.Capture methods with higher mortality rates were generally used in research aimed atinforming management decisions. Predation was directly responsible for most deaths, with theEurasian Sparrowhawk Accipiter nisus being the most common predator of birds captured innets. Migrating passerines occurring in large numbers at bird observatories contributed most tothe mortality rates in Denmark, with young birds on their first autumn migration beingespecially prevalent.Conclusions: Overall, our study confirms that bird ringing remains an acceptable method of datacollection and highlights the variation in mortality among species and methods. The results shouldbe used to inform working practices to minimize any associated mortality, as far as possible. more...

Most migratory birds return every year to the same breeding sites and some species show a similarly high fidelity to wintering grounds as well. Fidelity to stopover sites during migration has been much less studied and is usually found to be lower. Here, we investigate site fidelity and distance to previously visited sites throughout the annual cycle in the common cuckoo, a nocturnal trans-Saharan migrant, based on satellite-tracking data from repeated annual migrations of thirteen adult males. All birds (100%) returned to the same breeding grounds, with a median shortest distance of only 1 km from the locations in previous year. This was in strong contrast to a much lower and much less precise site fidelity at non-breeding sites during the annual cycle: In only 18% of the possible cases in all non-breeding regions combined, did the cuckoos return to within 50 km of a previously visited non-breeding site, with no significant differences among the main staging regions (Europe in autumn, Sahel in autumn, wintering in Central Africa, West Africa in spring, Europe in spring). The shortest distance to a previously visited non-breeding site differed among the staging regions with median shortest distances for the longest stopovers of 131 km [2;1223] (median [min;max]) in Europe, 207 km [1;2222] in Sahel in autumn and 110 km [0;628] in Central Africa. The distance to a previously visited staging site decreased with the time spent at the stopover in a previous year. Understanding the drivers of recurrence and site selection in migratory birds are important for guiding conservation efforts in this group but further studies are needed to establish whether the patterns observed in cuckoos are general among terrestrial migrants with continuous distribution of habitat. more...

Little is known regarding the migration routes of Siberian songbird populations. Here we provide the first geolocator tracking data for an Arctic Warbler breeding in Central Siberia and compare its movements with eight long-distance ring recoveries of this species. In autumn, the tracked individual migrated eastward to a stopover site in eastern Siberia, before migrating southward through Taiwan to its non-breeding sites in the Philippines and Indonesia. During spring migration, the bird spent at least one month at stopover sites in Mongolia, before migrating to its breeding site in June. Ring recovery data confirmed the movement between the Central Siberian breeding grounds and stopover sites in northern Mongolia. more...

1. Anthropogenic land cover change is a major driver of biodiversity loss, with urbanisation and farmland practices responsible for some of the most drastic modifications of natural habitats. The relative importance of different land covers for shaping insect communities, however, is unclear. 2. This study examines the effect of urban and farmland covers, along with land cover heterogeneity, at a landscape scale on species richness, evenness and biomass of flying insects using citizen science carnet sampling across Denmark. 3. Increasing urban cover had a negative effect on insect richness but an even stronger negative effect on biomass. Increased land cover heterogeneity did not mitigate the negative effect of urban cover. Insect assemblages also became more even with increased urban cover. Farmland cover had no significant effect on insect richness, evenness or biomass. 4. Based on our findings, the urban cover has a strong negative impact on insect communities, indicating that urbanisation could contribute to insect declines. Moreover, our findings indicate that insect loss occurs more through loss of biomass than loss of species, which may affect the ecosystem-level consequences of urbanisation. more...

Citizen science involves non-professionals assisting with scientific research, contributing data, and conducting experiments under professional guidance. In this paper, we describe the citizen science project DNA & life, based at the Natural History Museum of Denmark, which actively engages high school students in both fieldwork and advanced laboratory analyses by collecting and analyzing eDNA samples from marine environments across Denmark. The analysis is performed via species-specific real-time PCR and in a case study we present data gathered in the project from 2017-2023 with focus on the potential of eDNA detecting in use for species monitoring. The results include seasonal occurrence of Mnemiopsis leidyi and national distributions of selected species of particular ecological interest Perca fluviatilis, Anguilla anguilla, Neogobius melanostomus and Alexandrium ostenfeldii. In addition to the eDNA case study, we present a new way of conducting citizen science and eDNA analysis, as a development of the established DNA & life project. Local DNA laboratories are created to shorten the path from sampling site to laboratory facility, creating the possibility for Danish high schools to participate in a new version of the project. In close collaboration with the academic staff of the DNA & life project both teachers and students help develop facilities, protocols and laboratory analyses in an extreme citizen science and co-creation approach, where the participants are involved in a higher level of laboratory work and data analysis. Allowing high school students to perform intricate molecular lab analyzes through an extreme citizen science approach has demonstrated encouraging outcomes and potential for data of high quality in terms of sampling and analyzing eDNA with the purpose of species monitoring and conservation. more...

Using archived feathers from Norwegian, Swedish, and Greenlandic white-tailed eagles (Haliaeetus albicilla), we investigated long-term (1866-2015) spatiotemporal trends of polybrominated diphenyl ethers (PBDEs) and their methoxylated analogues (MeO-PBDEs). Concentrations of BDE 47 (constituting 47-65% of ∑PBDEs) were significantly increased in feathers from Sweden, while those of other congeners remained at similar levels between Sweden and Norway. Among the naturally occurring MeO-PBDEs, 6-MeO-BDE 47 exhibited higher levels in Sweden while 2′-MeO-BDE 68 concentrations were similar across regions. Concentrations of BDE 47 and 6-MeO-BDE 47 were not intercorrelated in Swedish eagles, highlighting the significance of anthropogenic input and natural origin, respectively, possibly associated with enhanced primary production in the Baltic region. Such a natural origin was further supported by the presence of MeO-PBDEs in 35 historical feathers originally collected from 1866 to 1957. Furthermore, in eagles from Norway and Sweden, less brominated PBDEs exhibited significantly increasing trends until the 1990s that declined considerably thereafter, whereas no apparent decrease was observed for BDE 153 or 154. By comparison, all PBDE congeners showed nonlinear but insignificant changes in Greenland. Additionally, the Swedish eagles showed significantly increased levels of ∑MeO-PBDEs, primarily driven by 6-MeO-BDE 47. Our findings indicate that further evaluation of the sources and impacts of more highly brominated PBDEs and MeO-PBDEs is warranted. more...

Citizen science offers enormous benefits to enhance public knowledge and understanding of science. Several opportunities to engage and share information with citizens are possible in citizen science projects. Recent evidence demonstrates however that individuals who participate in citizen science projects are demographically speaking not very diverse. For citizen science projects to successfully achieve their full potential in increasing public awareness and understanding of science, a wider social demographic needs to be engaged. We present a nationwide approach developed to achieve just that with respect to targeting and engaging residents in Denmark that did not previously have a prior connection to or interest in nature. Under the auspices of a campaign entitled Our Nature, our approach included the formation of a new, cross-sectoral partnership, and co-creating and implementing of a wide array of communication tactics and nature-based activities, including the development of a new citizen science project. Our cross-sectoral partnership allowed us to broaden the sectors of society that could be reached and develop cross-disciplinary activities to achieve goals for broad engagement. Extensive third-party evaluation revealed that 70% of the Danes interviewed across the country heard about Our Nature, and 70% of these gained more knowledge about Danish nature through the campaign. In addition to presenting our co-created projects and activities by working cross-sectorally and interdisciplinarily, we discuss the successes, challenges and limitations related to reaching our goal, based on evaluation results and our own experiences in citizen science and science communication. The citizen science project Denmark Explores that emerged from this campaign is used as a case study to demonstrate how our approach facilitated the broad engagement of citizens across the country––beyond the usual nature enthusiasts. more...

Climate change affects important biological processes, bird migration phenology being a particular well-documented one. While spring migration have been found to advance by numerous studies, autumn migration is less studied and show more variable change in timing. Few studies of autumn migration are based on data from after 2000, leaving the last two decades to be relatively less studied. Here, we investigate recent change in autumn migration phenology of European passerines. The most recent available bird ringing data from Denmark is used to analyse phenological change of median and late migration of 14 passerine migrants between 2003–2021. We find an overall delay of autumn migration, mainly driven by short-distance migrants. All short-distance migrants, one out of five medium-distance and three out of five long-distance migrants delay autumn migration. None of the included species advance autumn migration significantly. As climate change has continuously resulted in milder conditions in north-western Europe, we expect this to cause further effects on migration phenology also in recent decades. Our results provide novel insight into recent migration phenology trends, and the observed delay in long- distance migrants may illustrate a changed response to climate change. more...

Sporing af unger af danske Kongeørne Kongeørnen Aquila chrysaetos begyndte at yngle i Danmark i 1998 efter mange års fravær. Siden er mindst 53 unger regi- streret frem til 2021. Ynglebestanden har de sidste år ligget fast på 3-5 par. I dette studie undersøger vi de unge Kongeørnes spredning fra redeområdet i løbet af deres første leveår ved hjælp af data fra GPS/GSM-sendere monteret på fuglene. Des- uden rapporterer vi dødsårsager og overlevelsesrater. I alt har ni redeunger fået en GPS/GSM-sender monteret mellem 2015- 21. Vores resultater viser, at seks individer formåede at sprede sig fra redeområdet (> 5 km), mens tre døde i deres redeom- råder inden for deres første leveår. Ud af de ni individer var tre fortsat i live, fire er døde, og for to individer er status ukendt ved færdiggørelsen af dette manuskript. Fuglene fløj fra reden med en mediandato 3. juli (fordelt mellem 15. juni og 28. juli) og en median spredningsdato 2. december (fordelt fra 14. ok- tober til 21. april det følgende år). I en alder af seks måneder opholdt individerne sig i gennemsnit 99 km fra deres redeom- råder, men med stor individuel spredning fra 0,7 til 272 km. I en alder af et år opholdt individerne sig i gennemsnit 68 km fra deres redeområder ligeledes med en stor spredning fra 5 til 166 km. Vores resultater bekræfter en høj dødelighed i løbet af første leveår, som det tidligere er blevet vist i udenlandske studier. Resultaterne viser således, at det første leveår er kritisk for Kongeørnene, og viden om den store individuelle variation kan bidrage til bedre beskyttelse og forvaltning af Kongeørnen som ynglefugl i Danmark., The Golden Eagle Aquila chrysaetos established a breeding population in Denmark in 1998. Since then, at least 53 individu- als have fledged yet the breeding population has remained small at 3-5 pairs. In this study, we used GPS/GSM-tracking technology to investigate dispersal and present individual spatiotemporal histories during the first year of life of Danish Golden Eagles, with notes on survival and causes of mortality. In total, nine individuals were tagged with GPS/GSM-transmitters during a seven-year period (2015-2021). Our results show that six individuals managed to disperse (> 5 km from nesting site), while three individuals died before dispersal. Status at the end of the study for the tagged individuals was: three were alive, the fate of two was unknown, and four were dead. We found a median fledging date of 3 July (ranging 15 June to 28 July) and a median dispersal date of 2 December (ranging 14 October to 21 April the following year). Mean dispersal distance for all dispersed individuals from nest site was 99 km (range 0.7-272 km) at the age of six months. By the age of one year, mean distance from nest site was 68 km (range 5-166 km). Our study confirms high mortality during the first year as shown in a number of other studies and provides further evidence that first year dispersal period is critical for juvenile Golden Eagles. This study contributes important knowledge for future conservation and management of Golden Eagles breeding in Denmark. more...

Agricultural intensification and habitat degradation across Europe have caused declines since the 20th century in populations of birds adapted to open landscapes, such as the Red-backed Shrike (Lanius collurio). Effective conservation strategies require knowledge on species' breeding biology. To understand the status of the Danish breeding population better, we investigate which factors affect their breeding parameter (i.e. distribution, performance, post-fledging survival and behaviour). Our focus on the post-fledging period addresses present knowledge gaps due to the importance of this, yet under-studied, phase of passerines' breeding cycle. We studied breeding pairs on different habitat types with Denmark-wide Citizen Science data, complemented by data of local projects in Northern Zealand and Northern Jutland (Denmark). Significantly fewer pairs were found in agricultural habitats and more in forests, semi-natural open habitats and synanthropic habitats. Pairs in forests had a significantly higher breeding productivity compared to agricultural or semi-natural open habitats for data from the years 2000 to 2021. Some project sites showed significantly higher number of fledglings compared to others, indicating that these sites are potential core areas for breeding productivity. Over the last two decades, the mean breeding productivity across Denmark was stable with 2.3 fledglings per successful pair. The survival rate of ringed fledglings increased during the post-fledging period, likely due to their increase in more active and independent behaviour. The relatively low breeding productivity found in this study calls for further studies including detailed data from potentially secondary habitats like agricultural areas to understand the effects of habitat on population fluctuations. more...

SUMMARY: We tracked departures of European Robins Erithacus rubecula stopping over during spring migration at Skagen, Denmark, and facing a sea crossing of more than 50 km. The Robins stopped over on average for 3.8 days (range 1–14 days, n = 15) with departure days being slightly warmer than stopover days (1.5°C warmer, P = 0.003). Departures were concentrated in the evening, on average during astronomical twilight, and toward the northeast (µ = 33.3°, r = 0.499, P = 0.021). The mean northeasterly departure direction is close to the standard migration direction. Most birds probably crossed the sea to Sweden and we observed no obvious reversed departure directions. more...

Many species of amphibians in Northern Europe are threatened and the local distributions are rarely described in detail. Application of modern molecular methods provides an important supplementary tool for monitoring the distribution and diversity of amphibians. For this purpose, we designed, tested, validated, and optimized 14 species-specific assays on genomic DNA extracted from tissue samples to use for quantitative polymerase chain reaction (qPCR) setups targeting mitochondrial DNA from amphibians in freshwater samples. The tests confirmed species specificity for all assays. Considering a systematic definition of the limit of detection for each of the assays, the presented qPCR assays are unlikely to return false positive detection from any co-occurring species in northern Europe. For field validation, the qPCR assays were applied in a large-scale nationwide citizen science project in which sampling and qPCR analysis was carried out by high school students. Data from the citizen science project returned the expected results when compared to the known regional distribution of the target species and confirmed the presence of nine out of 14 Danish species of amphibians in the collected freshwater samples. Four out of 2550 qPCR test sets carried out by the high school students required a professional reanalysis in multiple replicates due to initial unexpected results. This emphasizes that efforts from citizen science may generate large amounts of valuable data, as long as the results are carefully scrutinized by experts. more...