Climate change is increasingly becoming a major threat to biodiversity. For example, most birds are currently forced to shift their breeding range to track suitable climatic conditions, but migratory birds have to face additional threats during migration and wintering period. This makes migratory species more vulnerable to climate change. Although demographic processes such as annual mortality can be significantly dependent on environmental conditions experienced by birds during migration and wintering, specific impacts of climate change during these stages of the annual cycle remain poorly investigated.
This case study focuses on Eurasian Skylark, a common farmland bird declining in Europe. As for other bird species wintering in Europe, we expect its winter distribution to shift northwards in relation to the increase in winter temperatures.
Distribution of skylarks wintering in France was characterized with a combination of INLA Bayesian hierarchical models and generalized additive mixed models. Our analysis is based on count data from a national survey, covering the whole country with 5,000 point counts sampled each year between 2000 and 2014.
Results/Conclusions
We found that skylark distribution in winter has significantly shifted northwards during the study period. There was no clear evidence linking this change to environmental factors. However, as temperatures have significantly increased, the hypothesis of a climate driven shift remains favoured.
This shift is most likely related to a reduction in migration distance, which has been suggested as one of the impacts of climate change on migration. Birds tend to winter closer and closer to their breeding grounds, which ultimately tend to increase the proportion of sedentary birds.
This phenomenon is likely to affect most bird species wintering in Europe, also known as short-distance migrants. Winter distribution shift means that these species have to face two different distribution shifts, both occurring in ecosystems with anthropogenic pressure in Europe, for farmland birds in particular. Conservation plans should therefore focus on protecting species habitat in areas with suitable future climatic conditions, not only within breeding distribution but also within the wintering one. In this context, there is also a need to investigate potential interactions between climate change and land use impacts, especially where climate change will have its most negative impact.