Background Landfills are a major subsidy for some animals, with implications for their life history and demography. Gulls feed extensively on food from landfills and closures are expected to have ecological consequences, but how this influences movement ecology is virtually unknown. Methods We used GPS-tracking to quantify foraging behaviour and habitat choice of lesser black-backed gulls (Larus fuscus) breeding at two colonies before and after closure of two nearby landfills. Results Following closure, gulls from both colonies travelled further and for longer to forage. Gulls also changed habitat selection, although this differed by colony - birds from one colony shifted to agricultural habitats, while at the other, increased their use of urban areas. These behavioural responses had no effect on adult body condition but hint at potential direct effects of higher foraging costs and indirect impacts by shifting to new habitats. Conclusions Our results demonstrate how landfill availability influences gull foraging movements and habitat selection. We also emphasize the value of biologging to detect rapid behavioural responses in contrast to more conventional demographic approaches, which is especially important for animals that spend the majority of their lives away from direct observation.
High pathogenicity avian influenza virus (HPAIV) caused the worst seabird mass-mortalities on record in Europe across 2021-2022. The northern gannet (Morus bassanus) was one of the most affected species, with tens of thousands of casualties in the northeast Atlantic between April-September 2022. Disease outbreaks can drastically modify the movement ecology of animals and diminish spatial consistency, thereby increasing the potential for disease transmission. To detect potential changes in movement behaviour, we GPS-tracked breeding adults following the initial HPAIV outbreak, at three of the largest gannet breeding colonies where major mortality of adults and chicks occurred (Bass Rock, Scotland, UK; Grassholm, Wales, UK; Rouzic island, Brittany, France). Crucially, GPS-tracked birds remained faithful to their breeding sites and did not prospect other breeding colonies. They performed regular foraging trips at sea, similar to their behaviour before the outbreak. Gannet foraging effort was nonetheless lower than in 2019, thus surviving birds may have benefited from reduced intra- and interspecific food competition. Breeding colony fidelity of adult northern gannets following HPAIV mass-mortalities suggests limited long-term capacity to virus spread, which may contrast with the behaviour of adults during the disease outbreak, or with that of younger individuals.
Despite urbanization's general erosion of biodiversity, towns and cities provide novel opportunities for some species. During the 20th century, gulls (Laridae) colonized urban areas around the world where they flourished. At the same time, some coastal populations declined. The reasons for this difference are not fully understood, partly because little is known about any ecological differences between urban and non‐urban gulls, such as their foraging ecology. Here we compare the movement ecology and habitat selection of Lesser Black‐backed Gulls Larus fuscus graellsii breeding at two neighbouring colonies – one urban and one coastal – in north‐west England. We used bird‐borne GPS loggers to first compare colony‐level movement behaviour and habitat selection and then investigated individual‐level habitat use. We observed clear colony‐level habitat segregation: urban breeders preferentially foraged in urban areas whereas coastal breeders foraged primarily in coastal habitats and avoided urban areas. Coastal breeders also had larger core and home‐ranges than urban breeders, possibly due to differences in colony size. However, we also found inter‐individual differences in habitat use, which may have important management implications. These findings suggest a link between nesting and foraging ecology, and thus management or environmental change altering food availability will impact gulls at the coastal and urban sites differently.
Vagrancy, where individuals occur outside of known population distributions, is a poorly understood ecological phenomenon. It can however be a key driver of site colonisation and range expansion. Evidence is emerging that presumed vagrant Siberian passerines in Western Europe, e.g. Richard’s Pipits Anthus ricardii, are colonists, with geolocator-tracked individuals returning to breed in Siberia after wintering in Western Europe. As such, ‘vagrancy’ patterns in these taxa could provide a model system to understand large-scale range shifts. For example, determining the origins of vagrant individuals and linking these to morphology and arrival date could help to identify the potential drivers of range dynamics. Here, we investigate the origins of vagrant Yellow-browed Warblers Phylloscopus inornatus (a migratory Siberian breeding passerine) in Western Europe by analysing stable hydrogen isotopes, morphology and phenology. We measure the isotopic patterns of feathers grown on the breeding grounds and their relation to those from two sub-species of Common Chiffchaff Phylloscopus collybita. We found that Yellow-browed Warblers have similar hydrogen isotopic signatures (δ2H) to the Siberian sub-species of Common Chiffchaff Phylloscopus collybita tristis and δ2H values did not overlap with those from the European nominate race of Common Chiffchaff Phylloscopus collybita collybita. There was weak evidence that variation in δ2H values was linked to differences in migratory distances in sampled Yellow-browed Warblers. The variation in δ2H values for Yellow-browed Warblers was similar to Chiffchaffs of the collybita and tristis sub-species. This suggests that Yellow-browed Warblers in Western Europe may originate from a relatively broad-front and not exclusively from an expanding western breeding range margin. It is unclear if vagrant Yellow-browed Warblers in Western Europe make viable return migrations to Siberia. If they are, the subset of individuals that become colonists could help us understand how vagrancy drives biogeographic processes, such as the establishment of novel migration routes.
1. Ongoing technological advances have led to a rapid increase in the number, type, and scope of animal tracking studies. In response, many software tools have been developed to analyze animal movement data. These tools generally focus on movement modelling, but the steps required to clean raw data files from different tracking devices have been largely ignored. Such pre-processing steps are often time-consuming and involve a steep learning curve. Moreover, decisions made at this early stage can substantially influence subsequent analyses. 2. Here we present an open-access, reproducible toolkit written in the programming language R for processing raw data files into a single cleaned data set for analyses and upload to online tracking databases. Additionally, we provide a Shiny app to enable appropriate parameter determination during data cleaning. 3. The toolkit is generalizable to different data formats and device types, uses modern 'tidy coding' practices, and has minimal dependencies. We provide a set of key principles and transparent, flexible code to flatten the learning curve associated with animal movement data processing, and produce robust, reproducible datasets. 4. Overall, we envision our resource as a time-saving approach that provides a reproducible pipeline from data collection to archiving, useful for anyone conducting animal movement analyses.
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