Trail is a term for the viscera, or internal organs, of game birds such as grouse, woodcock, and snipe. Historically, particularly in 19th and early 20th century British and European culinary practice, the trail — often including the liver and entrails — was sometimes retained during cooking to impart a richer flavor to both the bird and accompanying sauces or gravies.
Recipes from sources such as Mrs Beeton's Book of Household Management and Escoffier’s Le Guide Culinaire detail the judicious use of the trail, particularly for woodcock and snipe, sometimes spreading it on toast and serving it as a delicacy. The use of the trail declined in the later 20th century as culinary tastes shifted and food safety regulations became more stringent.