Kasper Thorup

• PhD Zoology
• Head of Section at University of Copenhagen

Synchronous fluctuations in species' abundance are influenced by synchrony in underlying rates of productivity and survival. However, it remains unclear how rate synchrony varies in space and time, contributes to abundance synchrony, and differs among species. Using long‐term annual count (number of adults captured), adult survival and productivity...

The Red-spotted Bluethroat ( Luscinia svecica svecica ) has a large breeding range in northern Eurasia and populations are known to migrate along the Indo-European or the East Asian flyway towards wintering areas in South and South-East Asia. The migration routes of birds breeding in Western and Central Siberia, where a migratory divide is expected...

Phenological plasticity—the ability of organisms to adjust breeding timing in response to environmental variability —is the primary mechanism for seasonal organisms as it enables to synchronize their life cycles with seasonal resource availability. Theory predicts that phenological plasticity should vary among populations because of environmental h...

Arctic breeding seabirds have experienced dramatic population declines in recent decades. The population of Arctic skuas (Stercorarius parasiticus) nesting on the Faroe Islands, North Atlantic, breed near the southern extent of their breeding range and are experiencing some of the largest declines. This is thought to be caused in part by increased...

Little is known about the migration routes of songbirds breeding in Siberia. We used satellite transmitters to study the migration of two White's Thrushes Zoothera aurea captured during the breeding season in the Ural Mountains, Russia. One of the devices transmitted after deployment, then fell silent in summer, and transmitted again during the bre...

Aim Ongoing climate changes represent a major determinant of demographic processes in many organisms worldwide. Birds, and especially long-distance migrants, are particularly sensitive to such changes. To better understand these impacts on long-distance migrants' breeding productivity, we tested three hypotheses focused on (i) the shape of the rela...

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 distributi...

The Earth Hologenome Initiative (EHI) is a global collaboration to generate and analyse hologenomic data from wild animals and associated microorganisms using standardised methodologies underpinned by open and inclusive research principles. Initially focused on vertebrates, it aims to re-examine ecological and evolutionary questions by studying hos...

Migrating animals perform astonishing seasonal movements by orienting and navigating over thousands of kilometres with great precision. Many migratory species use cues from the sun, stars, landmarks, olfaction and the Earth’s magnetic field for this task. Among vertebrates, songbirds are the most studied taxon in magnetic-cue-related research. Desp...

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 cyc...

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 Si...

Little is known regarding the migration routes of songbird populations breeding in Siberia. 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...

Steep declines in Arctic skua populations have been reported during the last half of the 20th century in the southern extent of their breeding range. We used 24 years of available ringing and re-encounter data from the Faroe Islands, North Atlantic, to determine if patterns in survival probabilities can be explained by large scale climatic events....

Bergmann’s rule states that homeotherms are larger in colder climates (which occur at higher latitudes and elevations) due to thermoregulatory mechanisms. Despite being perhaps the most extensively studied biogeographical rule across all organisms, consistent mechanisms explaining which species or taxa adhere to Bergmann’s rule have been elusive. F...

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 populati...

With the continued development of tracking technology and increasing interest in animal movement, our understanding of migration behavior has become more comprehensive. However, there are still many species that have not been well studied, particularly sea birds. Here, we present the first year-round Global Positioning System (GPS) tracking data of...

The global long‐term decline of migrant birds represents an important and challenging issue for conservation scientists and practitioners. This review draws together recent research directed at the Afro‐Palaearctic flyway and considers its implications for conservation. The greatest advances in knowledge have been made in the field of tracking. The...

Avian migratory processes are typically precisely oriented, yet vagrants are frequently recorded outside their normal range. Wind displaced vagrants often show corrective behaviour, and as an appropriate response is likely adaptive. We investigated the physiological response to vagrancy in passerines. Activation of the emergency life-history stage...

Background Long-distance migratory birds undergo complex annual cycles during which they must adjust their behaviour according to the needs and conditions encountered throughout the year. Yet, variation in activity throughout the entire annual cycle has rarely been studied in wild migratory birds. Methods We used multisensor data loggers to evalua...

Dispersal is a key life‐history trait for most species and is essential to ensure connectivity and gene flow between populations and facilitate population viability in variable environments. Despite the increasing importance of range shifts due to global change, dispersal has proved difficult to quantify, limiting empirical understanding of this ph...

Bird migrations are impressive behavioral phenomena, representing complex spatiotemporal strategies to balance costs of living while maximizing fitness. The field of bird migration research has made great strides over the past decades, yet fundamental gaps remain. Technologies have sparked a transformation in the study of bird migration research by...

Highly pathogenic avian influenza (HPAI) viruses of the A/Goose/Guangdong/1/1996 lineage (GsGd), which threaten the health of poultry, wildlife and humans, are spreading across Asia, Europe, Africa and North America but are currently absent from South America and Oceania. In December 2021, H5N1 HPAI viruses were detected in poultry and a free-livin...

Billions of birds undertake long-distance migration and the complexity of schedules has only recently become clear. Such movements occur as a response to seasonality but the ultimate drivers of these changing distributions remain difficult to study directly. Modeling seasonal distributions based fundamentally on climate and vegetation without param...

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmental change.

Avian migratory processes are typically precisely oriented, yet vagrants are frequently recorded outside their normal range. Wind displaced vagrants often show corrective behaviour, and as an appropriate response is likely adaptive. We investigated the physiological response to vagrancy in passerines. Activation of the emergency life-history stage...

The dynamics of wild populations are governed by demographic rates which vary spatially and/or temporally in response to environmental conditions. Conservation actions for widespread but declining populations could potentially exploit this variation to target locations (or years) in which rates are low, but only if consistent spatial or temporal va...

Highly pathogenic avian influenza (HPAI) viruses of the A/Goose/Guangdong/1/1996 lineage (GsGd), which threaten the health of poultry, wildlife and humans, are spreading across Asia, Europe and Africa, but are currently absent from Oceania and the Americas. In December 2021, H5N1 HPAI viruses were detected in poultry and a free-living gull in St. J...

Significance We combine tracks of a long-distance migratory bird with high–temporal resolution climate data to reconstruct habitat availability month by month for the past 120,000 y. The seasonal changes of suitable habitat in the past imply that continued seasonal migration was necessary during the glacial maxima. Genomic-based estimates of effect...

Dispersal is a key life-history trait for most species and essential to ensure connectivity and gene flow between populations and facilitate population viability in variable environments. Despite the increasing importance of range shifts due to global change, dispersal has proved difficult to quantify, limiting empirical understanding of this pheno...

Beginning in late 2017, highly pathogenic avian influenza (HPAI) H5N6 viruses caused outbreaks in wild birds and poultry in several European countries. H5N6 viruses were detected in 43 wild birds found dead throughout Denmark. Most of the Danish virus-positive dead birds were found in the period from February to April 2018. However, unlike the rest...

High fliers Migrating from hemisphere to hemisphere is a global strategy for many bird species. Despite allowing birds to track productivity, these long-distance movements bring them in contact with inhospitable regions such as deserts and oceans. Sjöberg et al. used geolocators to monitor flight in great reed warblers ( Acrocephalus arundinaceus )...

In migratory birds, constraints due to breeding are relaxed during the non-breeding season and thus, social behaviours and spatial associations are potentially more directly coupled to food resources and habitats. Use of space and territorial behaviour has rarely been studied in Afro-Palearctic migrants. Variation in strategies could exist among sp...

Wildlife conservation policies directed at common and widespread, but declining, species are difficult to design and implement effectively, as multiple environmental changes are likely to contribute to population declines. Conservation actions ultimately aim to influence demographic rates, but targeting actions towards feasible improvements in thes...

The Arctic is entering a new ecological state, with alarming consequences for humanity. Animal-borne sensors offer a window into these changes. Although substantial animal tracking data from the Arctic and subarctic exist, most are difficult to discover and access. Here, we present the new Arctic Animal Movement Archive (AAMA), a growing collection...

Ecological “big data” Human activities are rapidly altering the natural world. Nowhere is this more evident, perhaps, than in the Arctic, yet this region remains one of the most remote and difficult to study. Researchers have increasingly relied on animal tracking data in these regions to understand individual species' responses, but if we want to...

Unstructured citizen-science data are increasingly used for analysing the abundance and distribution of species. Here we test the usefulness of such data to predict the seasonal distribution of migratory songbirds, and to analyse patterns of migratory connectivity. We used bird occurrence data from eBird, one of the largest global citizen science d...

The regular fluctuation of resources across the Globe guides movements of migratory animals. To ensure sufficient reproductive output and maintain viable population sizes, migratory animals should match arrival at breeding areas with local peaks in resource availability. It is generally assumed that breeding phenology dictates the timing of the ann...

Common cuckoos Cuculus canorus are obligate nest parasites yet young birds reach their distant, species-specific wintering grounds without being able to rely on guidance from experienced conspecifics – in fact they never meet their parents. Naïve marine animals use an inherited navigational map during migration but in inexperienced terrestrial anim...

Understanding the spatiotemporal patterns of legacy organochlorines (OCs) is often difficult because monitoring practices differ among studies, fragmented study periods, and unaccounted confounding by ecological variables. We therefore reconstructed long-term (1939–2015) and large-scale (West Greenland, Norway, and central Sweden) trends of major l...

Individual responses of wild birds to fragmented habitat have rarely been studied, despite large-scale habitat fragmentation and biodiversity loss resulting from widespread urbanisation. We investigated the spatial ecology of the Short-toed Treecreeper Certhia brachydactyla, a tiny, resident, woodland passerine that has recently colonised city park...

Each year, billions of songbirds cross large ecological barriers during their migration. Understanding how they perform this incredible task is crucial to predict how global change may threaten the safety of such journeys. Earlier studies based on radar suggested that most songbirds cross deserts in intermittent flights at high altitude, stopping i...

We reconstructed the first long-term (1968–2015) spatiotemporal trends of perfluoroalkyl substances (PFAS) using archived body feathers of white-tailed eagles (Haliaeetus albicilla) from the West Greenland (n = 31), Norwegian (n = 66), and Central Swedish Baltic coasts (n = 50). We observed significant temporal trends of perfluorooctane sulfonamide...

Protandry, the earlier arrival of males at the breeding grounds relative to females, is common in migratory birds. However, due to difficulties in following individual birds on migration, we still lack knowledge about the spatiotemporal origin of protandry during the annual cycle, impeding our understanding of the proximate drivers of this phenomen...

Capsule: There were survival costs for adult European Robins Erithacus rubecula grounded at coastal sites following departure, but not for young Robins or Song Thrushes Turdus philomelos. Aims: To compare survival costs of crossing the Baltic Sea in autumn in adults and young of two passerines: the smaller European Robin and the slightly larger Son...

The spatiotemporal trends of mercury (Hg) are crucial for the understanding of this ubiquitous and toxic contaminant. However, uncertainties often arise from comparison among studies using different species, analytical and statistical methods. The long-term temporal trends of Hg exposure were reconstructed for a key sentinel species, the white-tail...

Aim To investigate the ecological relationship between breeding and wintering in specialist and generalist long‐distance migratory species, and the links between densities and range sizes. Location Denmark, Senegal and Ghana. Methods We use radio tracking to study spatial behavior and habitat use in three morphologically and ecologically similar...

Little is known about the variation within and among species of long-distance migrants in behavioural strategies and habitat choice on their non-breeding grounds. We report results from regular ringing operations carried out during the winter seasons 2009–2013 and transect counts in 2013, 2015 and 2016 in the Sudan Savanna Zone in Ghana. The best s...

A mortality event at the Christiansø colony in the Baltic proper killed 115 common eiders (Somateria mollissima) in mid-May 2016. To complement previous studies of incubating females, 39 males were necropsied and from a subsample of these a biochemical and haematological profile was obtained. The birds were emaciated and cachexic having a 50% reduc...

Presently, it is uncertain to what extent seasonal migrating birds contribute to the introduction of ticks and tick-associated pathogens in Denmark. To quantify this phenomenon, we captured birds during the spring and autumn migration at three field sites in Denmark and screened them for ticks. Bird-derived ticks were identified to tick species and...

The migration strategies of smaller, south European, Mediterranean birds are less well known than those of northern and central European birds. We used geolocators to map individual spatio-temporal migration schedules of three species breeding in the Iberian Peninsula: the White-rumped Swift Apus caffer, rufous-tailed Scrub-robin Cercotrichas galac...

Additional supporting information. Table S1. Individual and mean migration parameters of southern and northern species, respectively. Table S2. Mean and standard deviation (SD) of migration parameters in southern and northern species. Table S3. Wilcoxon-Mann-Whitney test results comparing different migration parameters of individual southern and no...

Key life-history events, such as breeding phenology, underlie much ecological research and inform conservation efforts. Simple methods that improve efficiency during breeding studies are valuable, particularly in remote locations and extreme climates. Building on an earlier study, we investigated the relationship between egg density and incubation...

Recent technological development has made it possible to pinpoint precise locations of small migratory songbirds throughout their annual cycle, providing the opportunity for improving our understanding of year-round habitat use. Here, we use GPS loggers to map the exact location and habitat use at stationary sites throughout the annual cycle of a l...

Timing of return to the breeding area presumably optimizes breeding output in migrants. How timing affects the other components of fitness — survival, has been comparatively little studied. Returning too early in spring is expected to be associated with high mortality in insectivorous migrants when weather conditions are still unsuitable. Yet, male...

Background Basic knowledge of detailed spatiotemporal migration patterns is lacking for most migratory bird species. Using the smallest available geolocator, we aim to map autumn migration and wintering areas of north European wood warblers Phylloscopus sibilatrix and compare the spatiotemporal pattern with recoveries of individuals ringed across E...

Insectivorous migrants breeding at northern latitudes often time the breeding period with the seasonal peak of food resources. Whether this general pattern transfers to movement behaviour during the breeding season requires detailed study from a local perspective. We investigated fine-scale environmental correlates of movements by six actively-bree...

Few species are adapted to high latitudes, and many over-winter in milder climates with migrations involving extensive barrier crossings. By escaping extreme conditions for the majority of the year, physiological and behavioural adaptations presumably need to be less pronounced. The snow bunting Plectrophenax nivalis is the most northerly breeding...

Migration of snow buntings. Migration of snow buntings from breeding grounds to breeding grounds (individuals represented by colour and logger ID). Identified stationary periods represented by solid line (—-) and periods of apparent movement by a dashed line (----), these include directed migration and nomadic behaviour. Breeding site longitude and...

Wintering environmental variables and land use. Environmental variables and land use for the duration of the wintering periods, with 70% Kernel Density Estimation of wintering grounds depicted by black polygon: (a) mean daily mean surface temperature (°C), (b) absolute minimum surface temperature (°C), (c) Percentage crop cover and (d) maximum snow...

Tracked birds deployment information and key timings. Tracked snow bunting deployment information and key timings of significant migration which were used to define Autumn, Winter and Spring periods. Total number of stationary periods (SP) and duration (in days) of wintering stationary periods, defined Autumn and Winter periods, and where known Spr...

Time series of snow buntings. Time series of identified migratory movements, stationary periods and nomadic behaviour. Key migration events are depicted by ▼ southwards and ▲ northwards, and coloured by departure from Svalbard, autumn (red), arrival at wintering grounds (blue), departure from wintering grounds, spring (green) and where known, depar...

Following ongoing technological advances, an increasing amount of full-year tracking data on individual migratory movements is becoming available. This opens up the opportunity to study how migration develops within individuals in consecutive years and the extent to which the migratory program is constrained. Such knowledge is essential for underst...

Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We track...

We used light-level-based geolocation to study the spatio-temporal behaviour of Siberian Rubythroats Calliope calliope breeding in the Amur region of the Russian Far East. Three retrieved devices revealed long-distance migrations, with southwestward movement from Amur through Northeast China in autumn, with the tracked individuals reaching their wi...

Despite many bird species migrating regularly within the African continent, in response to rainfall and breeding opportunities, documented evidence of the spatiotemporal patterns of such movements is scarce. We use satellite telemetry to document the year round movement of an intra-African migrant breeding in the savannah zone of sub-Saharan Africa...

Background For most Afro-Palearctic migrants, particularly small songbirds, spatiotemporal migration schedules and migratory connectivity remain poorly understood. We mapped migration from breeding through winter of one of the smallest Afro-Palearctic migrants, the willow warbler Phylloscopus trochilus, using geolocators (n = 15). ResultsBirds migr...

Changes in land-use and climate are threatening migratory animals worldwide. In birds, declines have been widely documented in long-distance migrants. However, reasons remain poorly understood due to a lack of basic information regarding migratory birds’ ecology in their non-breeding areas and the effects of current environmental pressures there. W...

Modelling the distribution of migratory species has rarely been extended beyond breeding and wintering ranges despite many species showing much more complex movement patterns with multiple stopovers. We aimed to create a temporally explicit species distribution model describing the full annual distribution cycle, and use it to model the complex sea...

In contrast to many other gull species, nominate lesser black-backed gulls (Larus fuscus fuscus, nLBBG) have shown generally decreasing population trends throughout their breeding area in northern and eastern Fennoscandia over the past decades and are now red-listed. Interspecific competition, predation, increased disturbance, organochlorine poison...

The current Northern Hemisphere migration systems are believed to have arisen since the last glaciation. In many cases, birds do not migrate strait from breeding to non-breeding areas but fly via a detour. All western European populations of red-backed shrikes Lanius collurio are assumed to reach their southern African wintering grounds detouring v...

Background Knowledge of spatiotemporal migration patterns is important for our understanding of migration ecology and ultimately conservation of migratory species. We studied the annual migration schedules of European nightjar, a large nocturnal insectivore and compared it with two other larger migratory insectivores, common swift and common cuckoo...

Knowledge of spatiotemporal migration patterns is important for our understanding of migration ecology and ultimately conservation of migratory species. We studied the annual migration schedules of European nightjar, a large nocturnal insectivore and compared it with two other larger migratory insectivores, common swift and common cuckoo. All speci...

Supplementary information on European nightjars. Data on individual birds (Table S1), stopover duration (Table S2) and definition of high-quality positions (Fig. S1).

Location estimates for individual European nightjars, common swifts and common cuckoos included in the study.

Being faced with unknown environments is a concomitant challenge of species’ range expansions. Strategies to cope with this challenge include the adaptation to local conditions and a flexibility in resource exploitation. The gulls of the Larus argentatus-fuscus-cachinnans group form a system in which ecological flexibility might have enabled them t...

Appendix - Here we provide two additional figures showing both the tracking data that was used for modelling habitat use with Maxent and the respective spatial predictions.

Migratory birds track seasonal resources across and between continents. We propose a general strategy of tracking the broad seasonal abundance of resources throughout the annual cycle in the longest-distance migrating land birds as an alternative to tracking a certain climatic niche or shorter-term resource surplus occurring, for example, during sp...

Being an obligate parasite, juvenile common cuckoos Cuculus canorus are thought to reach their African wintering grounds from Palearctic breeding grounds without guidance from experienced conspecifics but this has not been documented. We used satellite tracking to study naïve migrating common cuckoos. Juvenile cuckoos left breeding sites in Finland...

Number of ringed common cuckoos per country and country where southernmost recovery was obtained. Ringing periods are shown in the country column. Information obtained from European bird ringing atlases. (DOCX)

Tracking Data. (XLSX)

Timing and duration of the autumn migration periods of satellite-tracked juvenile and adult cuckoos in 2010–2014. Dates are given for arrivals and departures and the duration of each stage is given in days. ID = Bird identification with sex (F = female, M = male) followed by satellite-tag ID and last two digits of the tagging year in brackets. Age...

Morphometrics and ages of the young cuckoos. Measured when tagging (N = 13). Tag activation is given as days after tagging. (DOCX)

Location quality of positions included in the study. Number of locations and location quality (LQ A-B, 0–3; CLS 2007–2015) of cuckoos tracked from leaving the breeding areas to arrival on the winter grounds (as the southernmost stationary position) or end of transmission. (DOCX)

Supplementary Wind Analysis. (DOCX)

Fate of tagged cuckoos across studies. Logistic regression (Generalised Linear Model with logit link and binomial error distribution) of Finland post-fledging vs. UK post-fledging: parameter estimate of difference in location: 1.17; SD = 0.70; z = 1.68, P = 0.09. Finland juvenile autumn vs. UK adult autumn: parameter estimate of difference in age/l...