The rock ptarmigan (Lagopus muta) is a common and widespread breeding bird in Iceland. It is sedentary within Iceland, but extensive movements between breeding and wintering grounds occur. The ptarmigan’s most important breeding habitats are various types of grasslands and heathlands.
The population size of the ptarmigan varies greatly, both within and between years. By the summer’s end, Iceland’s ptarmigan population is typically three to four times larger than in the spring. Fluctuations in population size between years are greater. Interannual variation is cyclical in nature, but the length of these cycles has changed. Population cycles in rock ptarmigan currently last around 5 years. Before 2003, ptarmigan cycles lasted 10-12 years.
Ptarmigan counts in North-East Iceland – Click the double-pointed arrow in the lower right corner to expand the graph
The difference in density between high and low years can be up to 25-fold in some areas but is usually not as extreme. During the best ptarmigan years, the autumn population reaches well over a million birds, but the count can drop to fewer than 200 thousand individuals during low years. The country’s ptarmigan population was much bigger in the first half of the twentieth century, when it rose to 3-5 million birds during peak years. Due to long-term population decline, the rock ptarmigan is listed on Iceland’s Red List for Birds as near threatened (NT). A hunting moratorium in 2003 and 2004 was a response to the decline of the population. The ptarmigan census at Kvísker, SE Iceland, shows the general decline of the population within that region.
The ptarmigan census at Kvísker, SE Iceland – Click the double-pointed arrow in the lower right corner to expand the graph
The ptarmigan cycles are a natural phenomenon. Similar cycles are known among other species of small boreal or arctic herbivores, including other tetraonids, lagomorphs, voles and lemmings. Many ecologists believe that such population cycles are caused by food-web interactions, like plant-herbivore, herbivore-predator or herbivore-parasite. The gyrfalcon (Falco rusticolus) is a specialised ptarmigan predator and is probably one of the drivers of the ptarmigan cycle in Iceland. Other potential drivers include infestations by endoparasites like eimeriids (two species).
The ptarmigan and gyrfalcon cycles in North-East Iceland – Click the double-pointed arrow in the lower right corner to expand the graph
The rock ptarmigan is the only upland game bird in Iceland and has been hunted since the time of the island’s human settlement more than 1100 years ago. For most of this period, subsistence hunting was the only form of hunting practiced. Commercial hunting emerged in the late nineteenth century and prevailed until 2002. During the first half of this period, the European market grew steadily, and up to 250 thousand birds were exported per year. Export ceased in the Second World War, and after 1940 the domestic market took over. For many people in Iceland, the ptarmigan is a traditional Christmas dish, and up to one in four households in the 1990s served ptarmigan at this time of the year. From 2005, ptarmigan hunting has been permitted only for personal consumption and must take place within a set hunting period. All sale of ptarmigan and derived products is banned. The IINH assesses the status of the ptarmigan population on an annual basis to ensure a sustainable harvest.
Ptarmigan export, sales and hunting in North-East Iceland – Click the double-pointed arrow in the lower right corner to expand the graph