As owls are carnivores, their prey can contain various body parts that are difficult to digest and hold little nutritional value for the birds, such as bones, fur, beaks and claws. Instead of passing through the intestines of the bird these are coughed back up in the form of pellets.
Owls and other birds, particularly birds of prey, produce pellets. You may have seen these when out walking – they tend to be about the size and shape of a cocktail sausage. They are normally blackish in colour, and you might notice a shiny or fluffy appearance. Pellets are a great way of finding out more about owl behaviour, and Suffolk Wildlife Trust recently even used them when surveying local harvest mouse populations – the remains found in the pellets told them that the mice were definitely in the area, and even gave clues to where they were nesting.
Paul Wilkinson, head of Living Landscape, The Wildlife Trusts