Wetlands such as the World Heritage Site in the Wadden Sea include important habitats for breeding waterbirds. Its saltmarshes and adjacent conservation polders are used by thousands of breeding ...birds. However, some alarming population declines have been recorded during recent decades and previous studies found indications that predation pressure from red foxes (
Vulpes vulpes
) and more recently from invasive racoon dogs (
Nyctereutes procyonoides
) played an important role. The current study aimed to assess habitat utilisation by foxes and racoon dogs along the coast of the Wadden Sea. We equipped 21 foxes and seven racoon dogs with GPS collars and recorded a total of 37,586 (mean: 2,088) GPS fixes during a total of 2,617 (mean: 145) equipment days for red foxes and 3,440 (mean: 573) GPS fixes during a total of 272 (mean: 45) equipment days for racoon dogs. Foxes showed high individual variability in Kernel 95% home range sizes, with a mean of 172.2 ha (range: 3 to 824 ha) and little overlap among territories. Males had significantly larger home ranges than females, and there were no differences in home range sizes between adults (
n
= 14) and young (
n
= 4). Racoon dogs had smaller home ranges than foxes (mean: 52.8 ha). The preferred habitat type of both predators during daytime was the conservation polders along the Wadden Sea, while foxes also selected saltmarshes during the night. In contrast, both species avoided farmland areas. Foxes showed 20% of their activity during daylight hours and spent this time largely in areas with dense vegetation cover. None of the tagged individuals entered areas with particularly high bird densities (i.e. Wadden Sea islands or Halligen). However, our data suggest that foxes and racoon dogs frequently make use of linear structures such as dykes and dams and patrol along the tide line for carcasses. This suggests that at least single individuals of both species are prone to enter islands that are connected by dams to the mainland.
Omnivorous and opportunistic species may be good indicators of food availability. Gulls often use human‐impacted landscapes and may respond to changes by altering their feeding ecology. We ...investigated the foraging behavior of individual common gulls (Larus canus), focusing on their distribution during foraging and their selected habitat types. We tracked adult common gulls using GPS telemetry at their largest breeding colony in the southwestern Baltic Sea, Germany. Foraging habitats were analyzed from tracking data for three breeding seasons 2016, 2017, and 2019 and were compared with potentially available foraging habitats. Most breeding birds flew toward terrestrial areas. Feeding sites were located on average 11.7–14.3 km from the colony (range 0.9–36.5 km). Corn and sugar beet fields were used significantly and extensively compared with their availability in 2016 and 2017, while wheat, rape, and barley fields were used significantly less. Data from 2019 suggested seasonal shifts in habitat use. Birds spent between 30 and 1300 min per week at their preferred feeding sites, with significant differences between the major habitats selected. We found a stable, clear, multiyear pattern in common gull foraging behavior in relation to agricultural practices. Fields with little or no crop cover and thus access to the soil were preferred over fields with high crop cover. These results suggest that local food availability may be limiting further population increases in this species.
Most breeding Common Gulls (Larus canus) at their largest breeding colony in the southwestern Baltic Sea flew toward terrestrial areas for foraging. Fields with little or no crop cover and thus access to the soil were preferred over fields with high crop cover. These results suggest that local food availability may be limiting further population increases in this species.
Migration patterns in birds vary in space and time. Spatial patterns include chain, leapfrog and telescopic migration. Temporal patterns such as migration duration, number, and duration of stopovers ...may vary according to breeding latitude, sex, and season. This study aimed to verify these patterns in a long‐distance migrant, the Eurasian curlew Numenius arquata arquata, and to provide a synopsis of spatio‐temporal migration patterns in this species of concern throughout the East Atlantic Flyway. We tagged 85 adults with GPS‐data loggers in Germany, Poland, France and Estonia between 2013 and 2019. We computed the distance flown, linear loxodromic distance, duration, stopover number, total stopover duration, mean stopover duration, departure time and arrival time for 177 out of 187 tracks. On average (± standard deviation), spring migration occurred from 4 to 14 April (10.2 ± 8.4 days), curlews flew 3.623 ± 1.366 km, and had 5.8 ± 3.6 stopovers, with a duration of 29.4 ± 38.2 h per stopover, while autumn migration occurred from 18 to 29 June (10.9 ± 9.9 days), curlews flew 3.362 ± 1.351 km, and had 5.4 ± 4.0 stopovers, with 31.8 ± 32.3 h per stopover. Curlews displayed chain migration because wintering curlews maintained the latitudinal sequence to their breeding sites. Southern curlews had a longer nesting period due to their earlier arrivals. While spring arrival at breeding sites did not differ between the sexes, in autumn females departed earlier than males. Migration duration and distance, as well as stopover number and duration, showed a significant increase with breeding site latitude but did not differ between the sexes or between spring and autumn migrations, suggesting that curlews took a comparable amount of time migrating during both seasons. The high site faithfulness in curlews suggests that rapid autumn migration allows them to return to defend their winter foraging areas.
The Eurasian Curlew is an endangered long-lived shorebird breeding in grassland and moorland, with declining numbers across its range due to habitat loss and former hunting. In this context, any ...additional adult mortality can have a noticeable impact on population dynamics, hence on extinction risk. We report a case of a GPS-tagged individual which track revealed an unusual stopover at the bottom of a wind turbine along its migration route. The curlew rested hours in an unfavourable environment before moving to the adjacent coastal shore, then completed its migration journey the next day. In previous studies, GPS-tags helped to identify death casualties at wind farms, but to our knowledge this is the first detailed report of a non-lethal injury of a tagged animal by a wind turbine, probably by the vortex of rotors. This case alerts on the further potential impacts of wind farm development close to breeding, wintering and stopover sites frequented by Eurasian curlews and other birds. Any wind farm development project should consider the opportunity to avoid, reduce or compensate potential lethal and non-lethal impacts on wildlife.
•We document how a GPS-tagged migratory Eurasian Curlew interacted with a wind turbine.•Data collected by the GPS tag prove that the bird trajectory stopped at a wind turbine.•The outcome of the interaction was non-lethal as the Eurasian curlew completed its migratory journey the next day.•Eurasian Curlew is globally threatened due to widespread declines in breeding populations, so that assessment of all potential threats to adult survival is important.
Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and ...terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10-19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5-26.4 h (mean 8.7 h), and ranges varied from 3.0-79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5-333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period.
•Herring gulls prefer high bivalve biomass and low water levels for foraging.•Tracking and hydrodynamic data can be used to predict the occurrence of bivalve beds.•Herring gulls are suitable ...indicators for intertidal bivalve beds in the Wadden Sea.
Germany is an EU member state and is thus obliged to monitor and protect its marine and coastal areas in the context of international treaties (e.g. EU Marine Strategy Framework Directive, EU Natura2000 directives, Trilateral Monitoring and Assessment Programme, OSPAR) to achieve the good environmental status (GES). Suitable indicators thus need to be developed to assess the status of relevant ecosystems. Intertidal bivalve beds belong to the most productive habitats in the shallow coastal waters of the Wadden Sea but are highly dynamic and difficult to monitor. Extensive benthos and sediment sampling are required to study their development and distribution. We therefore evaluated the suitability of herring gulls (Larus argentatus) as a bioindicator species for monitoring these habitats. As flexible and opportunistic top-predators, herring gulls prefer to forage on intertidal flats and feed on bivalves (Cerastoderma edule, Mytilus edulis, Ensis leei) and crustaceans, with intertidal habitats near the breeding colony preferred during the incubation period. We used state of the art tracking devices to analyse habitat selection by herring gulls, and assessed how this was driven by biotic and abiotic factors. We then designed a habitat model to predict the occurrence of intertidal bivalve beds for directed monitoring, based on GPS logger data from herring gulls and hydrodynamic data. Both methods showed high correlations of herring gull foraging patterns with bivalve biomass and inundation time, depending on the distance from the breeding colony. The movement patterns of herring gulls clearly mirrored intertidal bivalve distributions. These results showed that combining GPS-logger data for top-predators, such as birds, with environmental data has great potential for monitoring and assessing the GES. We propose that herring gulls may be used as an indicator to locate bivalve beds in the Wadden Sea and to detect changes in the food web.
New wildlife telemetry and tracking technologies have become available in the last decade, leading to a large increase in the volume and resolution of animal tracking data. These technical ...developments have been accompanied by various statistical tools aimed at analysing the data obtained by these methods.
We used simulated habitat and tracking data to compare some of the different statistical methods frequently used to infer local resource selection and large-scale attraction/avoidance from tracking data. Notably, we compared spatial logistic regression models (SLRMs), spatio-temporal point process models (ST-PPMs), step selection models (SSMs), and integrated step selection models (iSSMs) and their interplay with habitat and animal movement properties in terms of statistical hypothesis testing.
We demonstrated that only iSSMs and ST-PPMs showed nominal type I error rates in all studied cases, whereas SSMs may slightly and SLRMs may frequently and strongly exceed these levels. iSSMs appeared to have on average a more robust and higher statistical power than ST-PPMs.
Based on our results, we recommend the use of iSSMs to infer habitat selection or large-scale attraction/avoidance from animal tracking data. Further advantages over other approaches include short computation times, predictive capacity, and the possibility of deriving mechanistic movement models.
Departure decisions in long-distance migratory bird species may depend on favourable weather conditions and beneficial resources at the destination location, overarched by genetic triggers. However, ...few studies have tried to validate the significance of these three concepts simultaneously, and long-term, high-resolution tagging datasets recording individual movements across consecutive years are scarce. We used such a dataset to explore intraspecific and intra-individual variabilities in departure and arrival decisions from/to wintering grounds in relation to these three different concepts in bird migration.
We equipped 23 curlews (Numenius arquata) wintering in the Wadden Sea with Global Positioning System data loggers to record their spatio-temporal patterns of departure from and arrival at their wintering site, and the first part of their spring migration. We obtained data for 42 migrations over 6 years, with 12 individuals performing repeat migrations in consecutive years. Day of year of departure and arrival was related to 38 meteorological and bird-related predictors using the least absolute shrinkage and selection operator (LASSO) to identify drivers of departure and arrival decisions.
Curlews migrated almost exclusively to Arctic and sub-Arctic Russia for breeding. They left their wintering site mainly during the evening from mid- to late April and returned between the end of June and mid-July. There was no difference in departure times between the sexes. Weather parameters did not impact departure decisions; if departure days coincided with headwind conditions, the birds accounted for this by flying at higher altitudes of up to several kilometres. Curlews breeding further away in areas with late snowmelt departed later. Departures dates varied by only < 4 days in individual curlews tagged over consecutive years.
These results suggest that the trigger for migration in this long-distance migrant is largely independent of weather conditions but is subject to resource availability in breeding areas. The high intra-individual repeatability of departure days among subsequent years and the lack of relationship to weather parameters suggest the importance of genetic triggers in prompting the start of migration. Further insights into the timing of migration in immatures and closely related birds might help to further unravel the genetic mechanisms triggering migration patterns.
Ship traffic in Northwestern European seas is intense and continuing to increase, posing a threat to vulnerable seabird species as a result of disturbance. However, information on species-specific ...effects of ship traffic on seabirds at sea is limited, and tools are needed to prioritize species and areas to support the integration of conservation needs in Marine Spatial Planning. In this study, we investigated the responses of 26 characteristic seabird species in the German North and Baltic Seas to experimental ship disturbance using large datasets collected as part of the Seabirds at Sea counts. We developed a Disturbance Vulnerability Index (DVI) for ship traffic combining indicators for species’ shyness, escape costs, and compensatory potential, and analyzed the relationships among shyness, escape costs, and vulnerability. The DVI was calculated using the following eight indicators: escape distance, proportion of escaping birds, proportion of birds swimming prior to disturbance, wing loading, habitat use flexibility, biogeographic population size, adult survival rate, European threat and conservation status. Species-specific disturbance responses differed considerably, with common scoters (Melanitta nigra) and red-throated loons (Gavia stellata) showing the longest escape distances and highest proportions of escaping individuals. Red-throated loon,black guillemot (Cepphus grylle), Arctic loon (Gavia arctica), velvet scoter (Melanitta fusca), and red-breasted merganser (Mergus serrator) had the highest DVI values, and gulls and terns had the lowest. Contrary to theoretical considerations, shyness correlated positively with escape costs, with the shyest species also being the most vulnerable among the species studied. The strong reactions of several species to disturbance by ships suggest the need for areas with little or no disturbance in some marine protected areas, to act as a refuge for vulnerable species. This DVI can be used in combination with distribution data to identify the areas most vulnerable to disturbance.
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