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Willow grouse ( Lagopus lagopus) and rock ptarmigan (Lagopus muta) are popular game birds in Sweden. I have analysed hunting statistics from Jämtland county in Sweden and investigated if there is a significant correlation between willow grouse density and Catch-Per-Unit-Effort (CPUE) by nationalities and type of permits. The included nationalities were Swedish, Nordic and non-Nordic hunters. Type of permits that were analysed were day-, municipality and county permits. There was no correlation between the grouse density and CPUE variables. However, significant correlations were found when correlating yearly number of harvested grouse  with the CPUE variables. For willow grouse, significant correlations were found between Swedish, Non-Nordic, day and municipality permit hunters and for rock ptarmigan, Swedish, Nordic, day and municipality permit hunters. I also found that international hunters was more effective than Swedish hunters, as well as hunters with day permit, which was true for both species. There were also differences between the CPUE variables between two time periods, 2004-2012 and 2013-2021. In the second period, the CPUE of Swedish hunters, day and municipality permit hunters have decreased for willow grouse. The CPUE also decreased for non-Nordic during the second period for rock ptarmigans. Significant difference in hunting pressure were also found between the two time periods, where the later period had slightly higher hunting pressure than the first period. The results of this study strengthened previous studies where no correlation has been found between the grouse density and CPUE.

From an ecological perspective, knowledge of demographic history is highly valuable because population size fluctuations can be matched to known climatic events, thereby revealing great insight into a species’ reaction to past climate change. This in turn enables us to predict how they might respond to future climate scenarios. Prominently, with the advent of high-throughput sequencing it is now becoming possible to assemble genomes of non-model organisms thereby providing unprecedented resolution to the study of demographic history and speciation. This thesis utilises four species of grouse (Aves, subfamily Tetraoninae) in order to explore the demographic history and speciation within this lineage; the willow grouse, red grouse, rock ptarmigan and the black grouse. I, and my co-authors, begin by reviewing the plethora of methods used to estimate contemporary effective population size (Ne) and demographic history that are available to animal conservation practitioners. We find that their underlying assumptions and necessary input data can bias in their application, and thus we provide a summary of their applicability. I then use the whole genomes of the black grouse, willow grouse and rock ptarmigan to infer their population dynamics within the last million years. I find three dominant periods that shape their demographic history: early Pleistocene cooling (3-0.9 Mya), the mid-Brunhes event (430 kya) and the last glacial period (110-10 kya). I also find strong signals of local population history – recolonization and subdivision events – affecting their demography. In the subsequent study, I explore the grouse dynamics within the last glacial period in more detail by including more distant samples and using ecological modelling to track habitat distribution changes. I further uncover strong signals of local population history, with multiple fringe populations undergoing severe bottlenecks. I also determine that future climate change is expected to drastically constrict the distribution of the studied grouse. Lastly, I use whole genome sequencing to uncover 6 highly differentiated regions, containing 7 genes, hinting at their role in adaptation and speciation in three grouse taxa. I also locate a region of low differentiation, containing the Agouti pigmentation gene, indicating its role in the grouse plumage coloration.