Life history traits and demography of a mountain bird under climatic variation

• Published in: Royal Society Open Science
• Main Author: Eriksen, Lasse Frost
• Other Authors: Nilsen, Erlend B., Ringsby, Thor Harald, Grøtan, Vidar, Moa, Pål Fossland
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: NTNU 2024
• Subjects: VDP::Matematikk og Naturvitenskap: 400; Arctic; Dovrefjell; Norway; Climate change; Tundra
• Online Access: https://hdl.handle.net/11250/3125313

Ongoing climate change can be expected to have major consequences for many species and ecosystems. Effects have been reported on reproduction, survival and movement ecology, with potential impacts for population dynamics and species interactions. Mountains are among the ecosystems that are expected to be particularly exposed to climate change, and observed changes include increased temperatures, shorter winters, reduced snow cover, and changed precipitation patterns. For many montane species there is limited information of the relationships between climatic variation and life history traits and demography. Such lack of knowledge makes it challenging to predict population dynamics under a changing climate, and potentially mitigate the effects of climate change. In this thesis, I investigated how short-term variation in climatic factors affects life history traits and demography of willow ptarmigan (Lagopus l. lagopus). Willow ptarmigan is a common and iconic bird species in northern hemisphere mountains, with long-term population declines at least in parts of its distribution range. It is resident to Arctic and low-alpine tundra, including the tundra-forest ecotone, but can perform shorter seasonal migrations within these environments. Empirical research on the detailed responses of ptarmigan to climatic variation is so far limited. I used data from two study areas in Norway, one historical (Dovrefjell, 1978-1994) and one ongoing (Lierne, 2015-2021), to test hypotheses related to reproductive strategies, movement strategies and survival in seasonal environments, with particular focus on the role of climatic variation. I found support for a common clutch size across individuals, meaning that the number of eggs laid was independent of body mass, age, and climatic variables. Although females with high body mass did not produce more eggs, they did produce more hatchlings from large clutches than females with low body mass. Further, I found that increased spring temperatures advanced onset of egg-laying, and that ...