to grouse moors and shooting. In recent decades the practice of using medicated grit and direct dosing of birds against an endoparasite, the strongyle worm or threadworm (Trichostrongylus tenuis), has become part of the management regime on many moors. As food The flavour of grouse, like most game birds, develops if the bird is hung for a few days after shooting and before eating. Roasting is the most common way to cook a grouse. The Cookery Book of Lady Clark of Tillypronie (1909) has 11 recipes for using grouse. The recipe "To cook old birds" runs as follows: Scientific study Because of their economic and social importance and some interesting aspects of their biology, red grouse have been widely studied. They were the subject of some of the earliest studies of population biology in birds, as detailed in The Grouse in Health and in Disease by Lord Lovat in 1911. Since the mid-20th century they have been subject to ongoing study by many organisations and individuals. Much work has been conducted by the Institute of Terrestrial Ecology in the eastern Cairngorms, and by the Game & Wildlife Conservation Trust in the Central Highlands. There are a wide range of research activities still going on today and a wealth of published literature exists on all aspects of grouse biology. Parasites and viruses The red grouse may be infected by parasites and viruses which severely affect populations. Strongylosis or 'grouse disease' is caused by the strongyle worm, which induces damage and internal bleeding after burrowing into the cecum. This endoparasite is often eaten with the tops of young heather shoots and can lead to mortality and poor condition, including a decrease in the bird's ability to control the scent it emits. First diagnosed in the UK in 2010, respiratory cryptosporidiosis, caused by Cryptosporidium baileyi, is present in approximately half the grouse moors in northern England, where it reduces natural survival and productivity of red grouse. Louping ill virus is a flavivirus (RNA virus), also known as sheep encephalomyelitis virus. Flaviviruses are transmitted by arthropods, and louping ill virus is transmitted by ticks. In red grouse, this virus can cause mortality as high as 78%. The main tick vector is the sheep tick Ixodes ricinus. Although traditionally tick-borne diseases are thought to be caused when the parasite bites its host, it has been shown that red grouse chicks can be affected when they