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.

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

Markus Varesvuo / Hawk Owl (Surnia ulula) regurgitating pellet before eating vole prey, Helsinki, Finland, December.

Alan Murphy/ BIA / Great Horned Owl (Bubo virginianus) regurgitating pellet, Texas

Philippe Clement / Short-eared owl (Asio flammeus) regurgitated pellet containing the remains of birds and mice, Scotland, UK, May

Michel Poinsignon / Eagle owl (Bubo bubo) pellet containing remains of its prey, Luxembourg. March.

Eric Medard / Little owl (Athene noctua) coughing up a pellet, France, July

Eric Medard / Little owl (Athene noctua) coughing up a pellet, France, July

Eric Medard / Little owl (Athene noctua) during the day on a wall, coughing up a pellet, France, October

Todd Mintz / Snowy owl (Bubo scandiaca) male expelling pellet on the Canadian prairie, Saskatchewan, Canada, March, sequence 3/3

Todd Mintz / Snowy owl (Bubo scandiaca) male expelling pellet on the Canadian prairie, Saskatchewan, Canada, March, sequence 2/3

Todd Mintz / Snowy owl (Bubo scandiaca) male expelling pellet on the Canadian prairie, Saskatchewan, Canada, March, sequence 1/3

Laurie Campbell / Tawny owl (Strix aluco) regurgitated pellet, Berwickshire, Scotland, October

Andy Sands / Short Eared Owl (Asio flammeus) coughing up an owl pellet. Lincolnshire, England, UK, February.

Andy Sands / Short Eared Owl (Asio flammeus) coughing up an owl pellet. Lincolnshire, England, UK, February.

Adrian Davies / Regurgitated pellet of Tawny owl (Strix aluco) showing remains of prey, Sussex, England, UK

Elio Della Ferrera / Common shrew bones {Sorex arabeus} found in pellet of Eurasian pygmy owl {Glaucidium passerinum}

Philippe Clement / Regurgitated Great horned owl pellets on taiga forest floor {Bubo virginianus} Denali NP, Alaska, USA.

Philippe Clement / Owl pellet showing wing cases of beetles, Belgium

Philippe Clement / Tawny owl pellet {Strix aluco} showing remains of mouse skeleton, Belgium

Philippe Clement / Tawny owl pellet {Strix aluco} showing remains of mouse skeleton, Belgium

Konrad Wothe / Barn Owl (Tyto alba) owl pellets made of regurgitated bones and fur, Germany

Mike Read / Regurgitated Pellets of Barn owl, Tawny owl, Short eared owl, Long eared owl and Little owl side-by-side for comparison

Mike Read / Contents of regurgitated Barn owl pellet {Tyto alba} UK. remains of woodmouse, vole, birds and short-tailed vole

Agustin Esmoris / Lesser Horned Owl (Bubo magellanicus) pellet, Argentina

Michael Quinton / Northern Hawk Owl (Surnia ulula) pellets, Alaska

Donald M. Jones / Mountain Pygmy-Owl (Glaucidium gnoma) regurgitating pellet, western Montana

Donald M. Jones / Mountain Pygmy-Owl (Glaucidium gnoma) regurgitating pellet, western Montana

Donald M. Jones / Mountain Pygmy-Owl (Glaucidium gnoma) regurgitating pellet, western Montana, sequence 1 of 3

Philippe Clement / Barn owl (Tyto alba) regurgitated pellets showing close-up detail of mouse skull, hair and bones found inside. Belgium

Philippe Clement / Barn owl (Tyto alba) regurgitated pellets showing close-up detail of mouse skull, hair and bones found inside. Belgium

Philippe Clement / Barn owl (Tyto alba) regurgitated pellets on hay bales in barn. Belgium

Philippe Clement / Barn owl (Tyto alba) regurgitated pellets showing bones and skulls of mice. Belgium.

Jose Luis Gomez de Francisco / Little owl pellets {Athene noctua} Spain - regurgitated remains of non-digestible prey food items eg bones and fur.

Brian Bevan / Little owl (Athene noctua) coughing up pellet whilst perching on branch in meadow at dusk, Bedfordshire UK, June.

Markus Varesvuo / Snowy owl (Bubo scandiaca) pellet, Canada January.

Eric Baccega / Long-eared owl chick regurgitating pellet (Asio otus) perched in tree. Alsace. France.

Alex Hyde / Owl pellet showing various rodent bones. Peak District National Park, Derbyshire, UK. June.

John Chan / Great horned owl (Bubo virginianus) regurgitating a pellet, Bolsa Chica Ecological Reserve, Southern California, USA, September.

John Chan / Great horned owl (Bubo virginianus) regurgitating a pellet, Bolsa Chica Ecological Reserve, Southern California, USA, September.