Steven David Miller / Sand bubble patterns created by Sand bubbler crabs (Scopimera inflata), Cape Hillsborough National Park, Queensland, Australia. September.

Sven Zacek / Ural owl (Strix uralensis) female feeding her young with part of a pellet it has regurgitated. Estonia, May.

John Chan / Great horned owl (Bubo virginianus) chick coughing up a pellet, Southern California, USA, June.

Steven David Miller / Sand bubble patterns created by Sand bubbler crabs (Scopimera inflata), Cape Hillsborough National Park, Queensland, Australia. September.

Suzi Eszterhas / Brandt's Cormorant (Phalacrocorax penicillatus) pellet of worms coughed up by cormorant International Bird Rescue, Fairfield, California

Eric Medard / Sparrowhawk (Accipter nisus) male regurgitating pellet, in forest, Pays de Loire, France

Sven Zacek / Ural owl (Strix uralensis) female and chick at nest, female regurgitating pellet. Southern Estonia. May.

Philippe Clement / Close up of regurgitated pellet from great skua (Stercorarius skua) showing seabird prey remains like bones and feathers, Scotland, UK, May.

Philippe Clement / Close up of regurgitated pellet from great skua (Stercorarius skua) showing seabird prey remains like bones and feathers, Scotland, UK, May.

Oscar Diez/ BIA / European Bee-eater (Merops apiaster) regurgetating pellet, Andalucia, Spain

Dave Bevan / Male Pied flycatcher (Ficedula hypoleuca) perched on a branch, disgorges pellet before flying out of frame, Carmarthenshire, Wales, UK, May.

Adrian Davies / Barn owl (Tyto alba) pellets, contents of approximately six pellets containing skulls and bones of voles, mice and shrews, and cockchafer beetle. UK. March.