Spatial consistency in drivers of population dynamics of a declining migratory bird

1. Many migratory species are in decline across their geographical ranges. Single-population studies can provide important insights into drivers at a local scale, but effective conservation requires multi-population perspectives. This is challenging because relevant data are often hard to consolidate, and state-of- the-art analytical tools are typically tailored to specific datasets. 2. We capitalized on a recent data harmonization initiative (SPI-Birds) and linked it to a generalized modelling framework to identify the demographic and environmental drivers of large-scale population decline in migratory pied flycatchers (Ficedula hypoleuca) breeding across Britain. 3. We implemented a generalized integrated population model (IPM) to estimate age-specific vital rates, including their dependency on environmental conditions, and total and breeding population size of pied flycatchers using long-term (34–64 years) monitoring data from seven locations representative of the British breeding range. We then quantified the relative contributions of different vital rates and population structure to changes in short-and long-term population growth rate using transient life table response experiments (LTREs). 4. Substantial covariation in population sizes across breeding locations suggested that change was the result of large-scale drivers. This was supported by LTRE analyses, which attributed past changes in short-term population growth rates and long-term population trends primarily to variation in annual survival and dispersal dynamics, which largely act during migration and/or nonbreeding season. Contributions of variation in local reproductive parameters were small in comparison, despite sensitivity to local temperature and rainfall within the breeding period. 5. We show that both short-and long-term population changes of British breeding pied flycatchers are likely linked to factors acting during migration and in nonbreeding areas, where future research should be prioritized. We illustrate the potential of multi-population analyses for informing management at (inter)national scales and highlight the importance of data standardization, generalized and accessible analytical tools, and reproducible workflows to achieve them. annual survival, comparative analysis, environmental effects, full annual cycle, integrated population model, LTRE, multi-population, pied flycatcherpublishedVersio

Life-cycle analysis of an endangered migratory goose to assess the impact ofconservation actions on population recovery

Evaluating the effectiveness of conservation actions is challenging for migratory species because a population can be impacted anywhere along its route. Conservation actions for the critically endangered Fennoscandian lesser white-fronted goose population include culling of red foxes in the breeding area and habitat improvements and reduction of illegal hunting in the non-breeding areas. One goal of the predator control strategy is to prevent adult birds from using an autumn migration route through western Asia, where mortality is believed to be higher than on the migration route through eastern Europe. We used 23 years of count data obtained at different staging areas to parameterize a seasonal state-space model describing the full-annual cycle dynamics of this population and evaluate whether the recent population recovery was linked to these conservation efforts. The results did not provide evidence that predator control influenced population recovery, as survival on the European route did not appear higher than on the allegedly riskier Asian route. However, adult survival at staging areas on both routes and at wintering sites may have improved in the last decade, suggesting a positive effect of the other conser- vation initiatives. These results emphasize the importance of including the non-breeding dynamics in population assessments of migratory species and highlight the challenge of evaluating the efficacy of separate conservation actions when a proper experimental design is unfeasible. Our study, which is a unique case of cross-national, coordinated conservation efforts, exemplifies how to model complex population dynamics to assess the influ- ence of costly conservation initiatives. Goose management State-space model Management evaluation Lesser whitefronted goose Unmarked individuals Non-breeding dynamic

Statistiske verktøy for prediksjon av årlig bestandsvekst og effekter av jakt på rødrev

Nater, C. R., Hofhuis, S. P., Grainger, M. & Ehrich, D. 2023. Statistiske verktøy for prediksjon av årlig bestandsvekst og effekter av jakt på rødrev. NINA Rapport 2330. Norsk institutt for naturforskning. Rødrev og mange andre små rovviltarter trives under pågående forandringer i både klima og menneskers arealbruk. Dette kan medføre forstyrrelse av økosystemprosesser i form av blant annet økt predasjon på småvilt, konkurranse med truede arter, og muligens spredning av zoonoser. For rødrev flere steder i Norge og i andre land brukes det av den grunn intensiv beskatning for å redusere bestander. Effekten av denne formen for predatorkontroll er derimot svært usikker og i noen grad kontroversiell, ikke minst fordi det finnes lite kunnskap om rødrevens bestands-dynamikk. For smårovvilt generelt er datagrunnlaget svært dårlig sammenlignet med andre høs-tede arter, men nye statistiske metoder gjør det mulig å få stort utbytte av tilgjengelig data gjen-nom integrert analyse. I dette prosjektet har vi utarbeidet en integrert populasjonsmodell for rød-rev på Varanger, som bygger på data som enkelt kan samles inn som en del av jakta, og brukt den for å estimere demografiske rater og bestandsutvikling over perioden 2004-2021. Videre har vi undersøkt underliggende drivere og satt opp et rammeverk for å utrede effekten av jakt og forvaltningsdrevne kontrolltiltak på rødrev. Resultatene viser at rødrevbestanden på Varanger-halvøya i gjennomsnittet har økt noe i perioden 2004-2021 til tross for intensiv beskatning. Dette skyldes ikke minst at bestandsvekst i liten grad var styrt av jaktmortalitet. Modellresultatene pe-ker derimot på at det var naturlig mortalitet og immigrasjon som var de sentrale driverne for bestandsdynamikk. Disse to demografiske ratene har to ting til felles: 1) de påvirkes i betydelig grad av miljødrivere, i dette tilfellet smågnagerforekomst og tilgjengelighet av reinsdyrkadaver gjennom vinteren, og 2) det finnes veldig lite overvåkingsdata som gir informasjon om de. Det er derfor svært viktig med videre, og muligens noe utvidet, overvåking av både rødrev og jakt-innsats. Videre kan det være verdifullt å vurdere tiltak som bygger ikke bare på beskatning, men som i tillegg tar høyde for miljøtilstand (med hensyn til forekomst av smågnagere og reinsdyrka-daver) hvert år. I tillegg framhever arbeidet viktigheten av å enkelt kunne oppdatere og gjenkjøre denne typen bestandsanalyse år etter år når nye data blir tilgjengelig, og levere en automatisert og reproduserbar arbeidsflyt for rødrev på Varanger, og muligens i andre områder, til dette formålet.Nater, C. R., Hofhuis, S. P., Grainger, M. & Ehrich, D. 2023. Statistical tools for prediction of annual population growth of and effects of hunting on red foxes. NINA Rapport 2330. Norsk institutt for naturforskning. Red foxes and many other small to medium sized predators thrive under changes in climate and human land use. This can lead to disruption of ecosystem processes in the form of, for example, increased pressure on small game, competition with and predation on threatened species, and possibly spread of zoonotic diseases. For red foxes in several areas of Norway, as well as in other countries, intense hunting, also called culling, is therefore used to reduce population size. However, the effect of such predator control measures is very uncertain and often somewhat controversial, not least because there is very little knowledge about red fox population dynamics. Data on small to medium-sized carnivores is typically scarce compared to other harvested species, but new statistical methods offer opportunities to make more efficient use of limited data through integrated analysis. In this project, we have developed an integrated population model for red foxes on the Varanger Peninsula, which uses data that can easily be collected as part of hunting, and used it to estimate demographic rates and population trends over the period 2004-2021. We further investigated the underlying demographic and environmental drivers and set up a framework for evaluating the effects of hunting and other management interventions efforts for red fox. Our results show that the red fox population on the Varanger peninsula has, on average, increased over the period 2004-2021 despite intensive hunting efforts, and that this is not least due to population dynamics being little affected by changes in hunting mortality. On the other hand, model results indicate that natural mortality and immigration were the primary drivers of population dynamics. These two demographic rates have two things in common: 1) they are substantially affected by environmental drivers, in this case rodent abundance and availability of reindeer carcasses over winter, and 2) there is very little monitoring data that can provide information on them. Continued and possibly extended monitoring (of both red foxes and hunting effort) is therefore very important. Furthermore, it may be valuable to consider management actions that not only focus on hunting, but that also take environmental conditions (rodent abundance and reindeer carcass availability) into account on a year-by-year basis. Additionally, this work highlights how important it is to be able to rerun this type of population analyses year after year as new data becomes available, and delivers an automated reproducible workflow for red foxes on Varanger to that end

Long-term mark-recapture and growth data for large-sized migratory brown trout (Salmo trutta) from Lake Mjøsa, Norway

Long-term data from marked animals provide a wealth of opportunities for studies with high relevance to both basic ecological understanding and successful management in a changing world. The key strength of such data is that they allow us to quantify individual variation in vital rates (e.g. survival, growth, reproduction) and then link it mechanistically to dynamics at the population level. However, maintaining the collection of individual-based data over long time periods comes with large logistic efforts and costs and studies spanning over decades are therefore rare. This is the case particularly for migratory aquatic species, many of which are in decline despite their high ecological, cultural and economical value.publishedVersio

Individual heterogeneity and early life conditions shape growth in a freshwater top predator

Body size can have profound impacts on survival, movement, and reproductive schedules shaping individual fitness, making growth a central process in ecological and evolutionary dynamics. Realized growth is the result of a complex interplay between life history schedules, individual variation, and environmental influences. Integrating all of these aspects into growth models is methodologically difficult, depends on the availability of repeated measurements of identifiable individuals, and consequently represents a major challenge in particular for natural populations. Using a unique 30‐yr time series of individual length measurements inferred from scale year rings of wild brown trout, we develop a Bayesian hierarchical model to estimate individual growth trajectories in temporally and spatially varying environments. We reveal a gradual decrease in average juvenile growth, which has carried over to adult life and contributed to decreasing sizes observed at the population level. Commonly studied environmental drivers like temperature and water flow did not explain much of this trend and overall persistent and among‐year individual variation dwarfed temporal variation in growth patterns. Our model and results are relevant to a wide range of questions in ecology and evolution requiring a detailed understanding of growth patterns, including conservation and management of many size‐structured populations

Long-term mark-recapture and growth data for large-sized migratory brown trout (Salmo trutta) from Lake Mjøsa, Norway

Long-term data from marked animals provide a wealth of opportunities for studies with high relevance to both basic ecological understanding and successful management in a changing world. The key strength of such data is that they allow us to quantify individual variation in vital rates (e.g. survival, growth, reproduction) and then link it mechanistically to dynamics at the population level. However, maintaining the collection of individual-based data over long time periods comes with large logistic efforts and costs and studies spanning over decades are therefore rare. This is the case particularly for migratory aquatic species, many of which are in decline despite their high ecological, cultural and economical value

Individual heterogeneity and early life conditions shape growth in a freshwater top predator

Body size can have profound impacts on survival, movement, and reproductive schedules shaping individual fitness, making growth a central process in ecological and evolutionary dynamics. Realized growth is the result of a complex interplay between life history schedules, individual variation, and environmental influences. Integrating all of these aspects into growth models is methodologically difficult, depends on the availability of repeated measurements of identifiable individuals, and consequently represents a major challenge in particular for natural populations. Using a unique 30‐yr time series of individual length measurements inferred from scale year rings of wild brown trout, we develop a Bayesian hierarchical model to estimate individual growth trajectories in temporally and spatially varying environments. We reveal a gradual decrease in average juvenile growth, which has carried over to adult life and contributed to decreasing sizes observed at the population level. Commonly studied environmental drivers like temperature and water flow did not explain much of this trend and overall persistent and among‐year individual variation dwarfed temporal variation in growth patterns. Our model and results are relevant to a wide range of questions in ecology and evolution requiring a detailed understanding of growth patterns, including conservation and management of many size‐structured populations

Close to open—Factors that hinder and promote open science in ecology research and education

The Open Science (OS) movement is rapidly gaining traction among policy-makers, research funders, scientific journals and individual scientists. Despite these tendencies, the pace of implementing OS throughout the scientific process and across the scientific community remains slow. Thus, a better understanding of the conditions that affect OS engagement, and in particular, of how practitioners learn, use, conduct and share research openly can guide those seeking to implement OS more broadly. We surveyed participants at an OS workshop hosted by the Living Norway Ecological Data Network in 2020 to learn how they perceived OS and its importance in their research, supervision and teaching. Further, we wanted to know what OS practices they had encountered in their education and what they saw as hindering or helping their engagement with OS. The survey contained scaled response and open-ended questions, allowing for a mixed-methods approach. We obtained survey responses from 60 out of 128 workshop participants (47%). Responses indicated that usage and sharing of open data and code, as well as open access publication, were the most frequent OS practices. Only a minority of respondents reported having encountered OS in their formal education. A majority also viewed OS as less important in their teaching than in their research and supervisory roles. The respondents’ suggestions for what would facilitate greater OS engagement in the future included knowledge, guidelines, and resources, but also social and structural support. These are aspects that could be strengthened by promoting explicit implementation of OS practices in higher education and by nurturing a more inclusive and equitable OS culture. We argue that incorporating OS in teaching and learning of science can yield substantial benefits to the research community, student learning, and ultimately, to the wider societal objectives of science and higher education.publishedVersio