Background: GPS telemetry has become the norm for the tracking of large-bodied bird species, whereas management and conservation of populations often rely on low-tech methods such as capture-mark-resighting (CMR). Direct evaluations of the comparability of the respective outcome from these methods remain rare despite being crucial for comparative studies and management decisions. Here, we investigated whether GPS tracking and CMR lead to same conclusions about seasonal migration and year-round space use. We chose greylag geese (Anser anser) as a study species, for which a long record of both coded neckband reports and GPS tracking are available, and whose management relies on CMR data.

Methods: Our data set was comprised of neckband reports and GPS tracks collected for birds from five capture sites in Sweden (n = 665 neckband birds; n = 156 GPS collar birds). We evaluated the similarity of movement metrics and year-round space use derived from continuous-time movement models and auto-correlated kernel density estimators. We further quantified overlap of spatial range estimates between tracking methods for the breeding period and the wintering season. We approximated spatial observation bias by contrasting range estimates estimated with and without the use of a debiasing algorithm.

Results: We found that estimates of space use derived from CMR and GPS tracking were in general agreement: average year-round space use for most individuals was similar even if means among tracking methods differed among all individuals per method (CMR: 5.07 x 10⁵ km²; GPS: 1.76 x 10⁵ km²) , and mean overlap of range estimates for summer and winter did not differ depending on whether the comparison was with the same, or differing tracking methods. Movement metrics differed considerably between methods whenever the CMR data captured behaviour at a different temporal scale than GPS (position & velocity autocorrelation), and else in agreement with GPS tracking (periodicity).

Conclusion: Our study suggests that the historical and current use of coded neckband data for greylag goose management decisions is appropriate regarding space use of migratory greylag geese in Europe. Understanding whether the existing reporter network can capture changes to the migratory behaviour of greylag geese including short-stopping of migration will however require additional in-depth analyses.

Animal movements contribute to the spread of infectious diseases and are driven in part by environmental conditions. We investigated the links among the environment, animal movement, and infectious disease dynamics in waterfowl, which are among the primary wildlife hosts of avian influenza viruses. By combining telemetry data on 4606 individuals from 26 waterfowl species with data on land cover, weather, and vegetation, we found that waterfowl moved less in areas of higher land cover heterogeneity and higher human population density. Moreover, predicted waterfowl movement distances were weakly but positively correlated with distances between detections of H5N1 highly pathogenic avian influenza in wild waterfowl, suggesting that environmental conditions might contribute to the spread of this disease via their effects on bird movements. By considering wildlife movements alongside other drivers of infectious disease dynamics, such as livestock production and human mobility, we move closer to predicting outbreaks and informing interventions.

Global products of land use and land cover (LULC) provide maps with a consistent classification, thereby allowing for comparisons of resource and habitat use of species over large spatial scales. While global LULCs tend to be evaluated extensively, the distribution ranges of species can extend into remote areas that are hard to access for ground truthing. It is unclear how adequate global LULCs are for mapping habitat of long-distance migrants throughout their entire range. Here, we investigated whether different global LULCs could successfully capture the known preferences of a migratory wetland specialist, the Eurasian wigeon (Mareca penelope), along the East Atlantic flyway. We evaluated how well five different global LULC products captured known wigeon habitat preferences using remote tracking data, and tested whether a further classification based on wetland expert knowledge can improve on their performance. We found that average performance of global LULC products varied greatly, with ESA WorldCover performing best with a 94% correspondence to wigeon habitat. All products performed best in the Tundra biome, and worse in Boreal as well as Temperate forests. In the latter areas, our wetland expert LULC classification provided improved results by explicitly considering small and temporary wetlands, and wetlands underneath vegetation. Overall, habitat use of habitat specialists can inform us about habitat types that are currently not considered in large-scale LULC maps. We suggest LULC mapping methods integrate information from tracking of wetland specialists for a better detection of small and temporary wetlands on a global scale.

Animal telemetry is maturing into a viable method for observing the ocean as it can be used to monitor both environmental conditions and biological metrics along the movement trajectories of marine animals. As part of the Cormorant Oceanography Project, we have augmented a biologging tag with an external fast response temperature sensor to collect ocean temperature profiles from the backs of foraging marine birds. Cormorants dive between 50 and 250+ times a day to forage for prey so they can provide hard-to-match temporal and spatial coverage of coastal ocean conditions within their foraging areas. We process tag measurements to obtain fundamental oceanographic data (e.g., temperature profiles, bottom soundings, surface current measurements). Together, we have tracked 17 marine bird species (including two Spheniscus penguins spp. and a sea duck), originating from 17 countries and foraging along the edges of all major oceans. Tagged birds' distribution included 191 MPAs in 26 countries, offering a unique ocean monitoring method to complement more widely used methods.

All foraging animals face a trade-off: how much time should they invest in exploitation of known resources versus exploration to discover new resources? For group-living central place foragers, this balance is challenging. Due to the nature of their movement patterns, exploration and exploitation are often mutually exclusive, while the availability of social information may discourage individuals from exploring. To examine these trade-offs, we GPS-tracked groups of greater spear-nosed bats (Phyllostomus hastatus) from three colonies on Isla Col & oacute;n, Panam & aacute;. During the dry season, when these omnivores forage on the nectar of unpredictable balsa flowers, bats consistently travelled long distances to remote, colony-specific foraging areas, bypassing flowering trees closer to their roosts. They continued using these areas in the wet season, when feeding on a diverse, presumably ubiquitous diet, but also visited other, similarly distant foraging areas. Foraging areas were shared within but not always between colonies. Our longitudinal dataset suggests that bats from each colony invest in long-distance commutes to socially learned shared foraging areas, bypassing other available food patches. Rather than exploring nearby resources, these bats exploit colony-specific foraging locations that appear to be culturally transmitted. These results give insight into how social animals might diverge from optimal foraging.

Anthropogenic environments such as wastewater treatment plants (WWTPs) and landfills are sources of antimicrobial resistance (AMR). Black-headed gulls (Chroicocephalus ridibundus) frequently use WWTPs and may be vectors for AMR. We used GPS tracking data for 39 gulls for up to 8 months, combined with a shedding curve, to study sources and dispersal distances of AMR in Iberia. The gulls used 21 different WWTPs (684 visits) and three landfills (21 visits). Areas of high risk of AMR dissemination were an average of 25 km from the infection source, with a maximum of 500 km. Solar saltworks and natural waterbodies were particularly exposed to AMR dissemination, followed by agriculture, sports facilities, and tourist beaches. There was important variability between individual gulls in their habitat specialization, and which WWTPs they visited. Studying the spatial movements of gulls after visiting WWTPs and landfills helps pinpoint sensitive locations where pathogen transmission is most likely. © The Author(s) 2024.

Objectives: The recent detection and expansion of West Nile virus (WNV) and Usutu virus (USUV) in the Netherlands, Germany, and Austria point to the likelihood of the viruses spreading to Northern Europe. Migratory birds and ornithophilic mosquitoes may spread these viruses to new areas. We sampled birds during the spring and autumn bird migration of 2021 in Southern Sweden to investigate the risk of the introduction of mosquito-borne zoonotic avian viruses like WNV and USUV.

Methods: We collected blood samples from 1775 birds comprising 59 species and determined the seroprevalence of WNV using a competitive enzyme-linked immunosorbent assay (ELISA). WNV and USUV belong to the Japanese encephalitis serocomplex, and antibodies against both viruses are detected in the WNV ELISA. Focus-forming assays or fluorescence-based neutralization assays were performed to verify ELISA results and to differentiate between antibodies against WNV and USUV.

Results: We found nine (0.51%) samples to be WNV-antibody-positive. Cross-neutralization experiments with WNV and USUV confirmed that seven (0.41%) had WNV-neutralizing antibodies and two (0.11%) had USUV-neutralizing antibodies. Interestingly, the two samples had neutralizing antibodies of both viruses. All samples but one with anti-flavivirus antibodies came from long-distance migrants wintering in sub-Saharan Africa. Antibodies were detected in samples taken during spring and autumn and only in adult birds.

Conclusion: The findings show that migratory birds in Sweden have been exposed to WNV and USUV. © 2025 Elsevier B.V., All rights reserved.

Background Small songbirds respond and adapt to various geographical barriers during their annual migration. Global flyways reveal the diverse migration strategies in response to different geographical barriers, among which are high-elevation plateaus. However, few studies have been focused on the largest and highest plateau in the world, the Qinghai-Tibet Plateau (QTP) which poses a significant barrier to migratory passerines. The present study explored the annual migration routes and strategies of a population of Siberian Rubythroats (Calliope calliope) that breed on the north-eastern edge of the QTP. Methods Over the period from 2021 to 2023, we applied light-level geolocators (13 deployed, seven recollected), archival GPS tags (45 deployed, 17 recollected), and CAnMove multi-sensor loggers (with barometer, accelerometer, thermometer, and light sensor, 20 deployed, six recollected) to adult males from the breeding population of Siberian Rubythroat on the QTP. Here we describe the migratory routes and phenology extracted or inferred from the GPS and multi-sensor logger data, and used a combination of accelerometric and barometric data to describe the elevational migration pattern, flight altitude, and flight duration. All light-level geolocators failed to collect suitable data. Results Both GPS locations and positions derived from pressure-based inference revealed that during autumn, the migration route detoured from the bee-line between breeding and wintering grounds, leading to a gradual elevational decrease. The spring route was more direct, with more flights over mountainous areas in western China. This different migration route during spring probably reflects a strategy for faster migration, which corresponds with more frequent long nocturnal migration flights and shorter stopovers during spring migration than in autumn. The average flight altitude (1856 +/- 781 m above sea level) was correlated with ground elevation but did not differ between the seasons. Conclusions Our finding indicates strong, season-dependent impact of the Qinghai-Tibet Plateau on shaping passerine migration strategies. We hereby call for more attention to the unexplored central-China flyway to extend our knowledge on the environment-migration interaction among small passerines.

The Little Stint Calidris minuta is an Arctic wader species that migrates through the Baltic Sea region towards wintering areas in North and West Africa and the Mediterranean region. We use a 75-year trapping series, comprising 4,791 Little Stints on autumn migration, from Ottenby Bird Observatory in Sweden to illustrate long-term trends in abundance, phenology, and morphometrics. Numbers of trapped juveniles dropped from median 31 (mean 74) in 1946–1999 to median 1.5 (mean 3.5) birds in 2000–2020, while the number of adults was generally low and without trends. Rolling window analyses showed that the drop in juveniles started around 1984, and from 1993 onward the median never exceeded seven juveniles/year (25 %-quantile: 0–1; 75 %-quantile: 4–55). Moreover, adult birds advanced their passage on average 0.48 days per year, passing 26 days earlier in 2020 than in 1946. Earlier migration of adults and decreased numbers of juveniles suggest low reproductive output in recent decades. Morphometric data of recaptured birds show that Little Stints on stopover at Ottenby gain fuel at a speed close to the theoretical maximum, strongly indicating that the conditions at the trapping site remain favourable for foraging waders.

Analysis of long-term datasets on bird populations can be used to answer ecological and management questions that are useful for conservation. Tanguar Haor (9500 ha) is one of the major freshwater wetlands in Bangladesh and supports a large number of migratory and resident waterbirds. Because of its unique ecological and economic values, it is arguably the most notable wetland in the floodplains of northeast Bangladesh and in the region. This Ramsar site supports globally important populations of threatened waterbirds, such as the Baer's Pochard Aythya baeri, Common Pochard Aythya ferina, Falcated Duck Mareca falcata, Ferruginous Duck Aythya nyroca, Oriental Darter Anhinga melanogaster, and Black-tailed Godwit Limosa limosa. Considering the international significance of this site, knowledge gaps on waterbird population trends, and key ecological factors, we conducted waterbird census between 2008 and 2021 to identify priority sites for conservation, population trends of resident and migratory waterbirds, and environmental factors that influence their abundances. We recorded a total of 69 species of waterbirds (maximum count of 166,788 individuals in 2013) and assessed population trends of 47 species. Of these, peak counts of 15 species exceeded the 1% threshold of their Asian-Australian Flyway population estimates. Most species (59%) showed a declining trend, including the critically endangered Baer's Pochard and the vulnerable Common Pochard, and 16 species (41%) showed an increasing trend. Based on the abundance and species diversity, we have identified Chotainna beel and Lechuamara beel as conservation priority sites within the Haor complex and discuss key threats to these areas. We also offer evidence that adjusting water-level management to annual rainfall patterns could be a useful intervention for waterbird management. Involving local communities in conservation efforts by creating bird sanctuaries within the Haor complex will strengthen waterbird conservation in the country and along the East Asian-Australian Flyway.