“Complete” refers to the British Isles, but this guide will be useful in North America as well, since many of the same birds or close relatives cast up pellets with similar contents. In addition, the book has valuable natural history showing what we can learn about the ecology of any species whose pellets we examine and about the dynamics of the ecosystem it inhabits.
Pellets are the regurgitated undigested remains of any bird’s food, be it animal or vegetable, and even mineral, since some pellets include bits of sand or stone that birds deliberately or incidentally swallow. Owls and cormorants produce 1 or 2 pellets per day, gulls and skuas 1 per meal, and some sandpipers 1 every 20 min. The contents vary not only by diet, but also based on whether a bird swallows its food whole, like owls, or tears it apart and eats it in small bits,...