Population dynamics of the White-winged Snowfinch: A cold weather specialist in a warming world

The habitat of the highly specialised White-winged Snowfinch is currently undergoing dramatic changes. We investigate the effects of these changes on breeding biology and population dynamics and explore possible measures to support the declining population.

Aims

The White-winged Snowfinch (hereafter referred to as ‘Snowfinch’) is ecologically and physiologically adapted to the harsh climatic conditions of high elevations. It roosts in deep rock crevices where it is sheltered from the wind and feeds on fatty plant seeds. Its nest is insulated by a thick layer of dry grass lined with Ptarmigan feathers or wool. The Snowfinch times its breeding period such that the rearing of the young coincides with the snowmelt. Along the edges of melting snow, it finds plenty of high-energy Tipulidae larvae to feed its young. Climate-induced changes in snow conditions affect availability and accessibility of these insects larvae. In addition to the alterations of its habitat, local disease outbreaks have been reported for Snowfinches, recently. The causative agents, Salmonella and Trichomonas, were observed for the first time to infect this bird species.

Our goal is to investigate how such environmental changes affect the population dynamics of the Snowfinch. The project addresses the three most important elements of population dynamics: reproduction, survival and movements. Of particular interest are correlations between snow conditions, weather and habitat on the one hand and clutch size, hatching rate as well as growth and survival on the other hand.

Approach

The investigation of seasonal differences in the survival rate and how these are related to environmental factors requires tracking marked individuals over the course of the year. To this end, in 2015 we started marking Snowfinches at various locations. This allowed us to establish a suitable study population for measuring survival rates and spatial activity of an alpine species that else is difficult to study. Growth and survival of nestlings are investigated in a nest box population. Over the last years, a good number of boxes were repeatedly occupied. Analyses of the data sets collected over many years by our volunteers reveal how environmental factors, such as snow cover and weather, correlate with the time of breeding. It is of high interest to us to pinpoint factors which the Snowfinch relies on for the timing of its brood. Shedding light on these factors will allow us to estimate how well the species is able to react to changes in the phenology of the nestling food. In addition, we intend to correlate population changes with changes in vegetation, climate and land use. Such correlations will elucidate factors that are most relevant in determining population dynamics. Microbial and molecular methods will help detecting the causing agents of the newly observed diseases from saliva and faecal samples. Infected Snowfinches and contaminations at bird feeders will be identified in this way. Knowledge of the distributions and extent of the diseases enables determining their possible impact on the Snowfich population.

Significance

The present study will shed light on how an alpine specialist reacts to changing environmental conditions. This will enable us to estimate future population trends and identify possible measures to support the population.

Over the past decades, various monitoring projects in Switzerland and abroad showed a decline of the Snowfinch population in the Alps. About 15 % of the European subspecies of the Snowfinch breed in Switzerland. This implies that our country has a high responsibility for the species’ conservation. With the current project, we take on this responsibility. We investigate the reasons for the Snowfinch population’s decline, how its future could look like, and what kind of measures can be taken to support this character species of the Alps.

Results

Our findings revealed that the feeding rate increased in the course of progressing snowmelt. At the same time, the nestling diet changed. While during snowmelt, large loads of Tipulidae larvae have been brought to the nest, smaller quantities of a wide range of insects and their larvae were fed to the nestlings after the snow disappeared (download the poster). Analyses of long-term citizen science data (ornitho.ch) showed that at elevations higher than 2300 m a.s.l. most broods hatched during snowmelt, the time with highest food availability. At lower elevations, Snowfinches seem to have difficulties to time their brood according to favourable environmental conditions. Analyses of data from marked Snowfinches have shown that females disappeared in years with warm and dry summers. In contrast, the proportion of males returning to the study area was independent of rain or temperature. These results are among the first direct indications that altering environmental conditions caused by climate change have a negative impact on Snowfinches. Thus, the future of this highly adapted alpine species most likely depends on our ability to reduce the extent of the ongoing climate warming and conservation measures we are willing to take.

Project management

Fränzi Korner-Nievergelt (senior scientist)

Project team

Sebastian Dirren (research scientist), Anne-Cathérine Gutzwiller (Master student), Carole Niffenegger (Master student), Elisenda Peris Morente (field assistant), Christian Schano (PhD student), Irmgard Zwahlen (scientific collaborator)

Partners

snowfinch.eu
PD Dr. Sabine Hille, Universität für Bodenkultur Wien, Österreich
Maria del mar Delgado, Universität de Oviedo, Mieres, Spanien
Alpfor
Naturmuseum Chur
Schatzinsel Alp Flix 
SLF

Financial support

Stiftung Yvonne Jacob

Swarovski Optik Schweiz

An anonymous foundation

Publications