Migration strategies and circannual patterns of habitat use of snowfinches (montifringilla nivalis nivalis) in a patchy alpine landscape
- Autores: Chiara Bettega
- Directores de la Tesis: María del Mar Delgado Sánchez (dir. tes.), Mattia Brambilla (codir. tes.)
- Lectura: En la Universidad de Oviedo ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Alfredo González Nicieza (presid.), Juan Carlos Illera Cobo (secret.), Sabine Marlene Hille (voc.), Beatriz Arroyo López (voc.), Dan Chamberlain (voc.)
- Programa de doctorado: Programa de Doctorado en Biogeociencias por la Universidad de Oviedo
- Materias:
- Enlaces
- Tesis en acceso abierto en: RUO
- Resumen
Biodiversity is intimately linked with ecosystem functioning, and thus with human well-being. Changes are occurring at a worrying rate, in response to overexploitation, pollution, species invasions, habitat fragmentation and alteration and climate change. Species responses are not always linear or instantaneous, nor they are equal at any spatial scale. Detection of early-warning signs of critical biodiversity changes is thus needed and the monitoring of essential biodiversity variables (EBVs) has been proposed as a tool to capture major dimensions of biodiversity change.
Mountain regions are among the richest terrestrial ecosystems in terms of biodiversity and most threatened by global change. They are complex and heterogeneous systems, which act as cradles, barriers or bridges and refuges for species and they can also influence biodiversity at a continental scale. Anthropogenic modification of mountain habitats and climate change are posing serious threats to these ecosystems. Species living in mountain regions are already responding through e.g. shifts in phenology or upslope migration. However, the speed at which climate is changing, together with the pressure of habitat alterations might challenge their response abilities. Due to the complexity of species and community dynamics, the actual effects of climate change on mountain biodiversity, especially when interacting with other stressors, are extremely difficult to predict. Moreover, the harshness of mountains hampers research activities. Thus, there is often a lack of understanding of species ecology, which is essential for accurate monitoring and conservation. There is also a general lack of research into the relationships between species’ functional traits and ecosystem function. Identifying rare species which contribute disproportionately to ecosystem function is crucial for establishing conservation priorities.
The aim of this doctoral thesis is to broaden the knowledges about (i) the distribution range, (ii) the habitat specificity, (iii) the movement strategies and (iv) the group dynamics of one of the most emblematic alpine bird species, the snowfinch Montifringilla nivalis nivalis, specifically studying the populations of the Alps, the Apennines, the Cantabrian Mountains and the Spanish Pyrenees.
We also introduced our study with an insight into the Holarctic mountain bird communities, their functional diversity and the functional rarity of their species. Functional uniqueness is independent from the geographical distribution of mountain species and it increases along the elevational gradient, following increasing specialization in high-elevation taxa adaptations. We found that the current breeding distribution of the snowfinch is considerably greater than the potential distribution obtained by modelling breeding records with climatic, topographic and land-cover variables. Discrepancies are particularly evident in eastern Europe, where there is a lack of monitoring. Southern populations are more fragmented and isolated and thus at major risk because of global warming. Through the study of circannual use of habitat of the snowfinch at different spatial scales, we found that the species depends on high-elevation habitats throughout the year, although with a higher plasticity during winter. Considering the lower elevation of southern Europe ranges, populations living in these areas could experience higher range contraction. We also found that the species is capable of latitudinal winter movements in form of partial migration, that connect the population of the Alps with those of the Iberian ranges (e.g. Pyrenees and Cantabrian Mountains) and that could potentially reduce genetic drift, with important implications for the resilience and persistence of these populations. Yet, these movements seem to be triggered by weather conditions, i.e. snowfinches move when winter conditions in the Alps are harsher. Global warming might thus reduce migration propensity, with effects on population demography, structure and heterogeneity. Our results suggest that climate change seems also to affect social dynamics. In fact, snowfinches seem to respond to warmer conditions through reduction of size and duration of flocks. This could increase asynchrony with the peak of resource availability and accessibility, with consequences on breeding performances. Moreover, if partial migration is sex or age conditioned, changes in social dynamics could also affect movement strategies.
This doctoral thesis brings novel insights into the ecology of the snowfinch which can help implementing future monitoring and conservation plans. It also represents the starting point for future research focused on better understanding population connectivity and dynamics, identifying isolation phenomena and deepening the knowledges about the responses of the species to climate change.
