Barred Owl

Associated Smithsonian Expert: Gary R. Graves, Ph.D.

Dr. Gary Graves had an early childhood fascination with birds that eventually led him to his role as curator of birds at the National Museum of Natural History.

Photo by Don Hurlburt, Smithsonian Institution

Dr. Gary Graves is a research zoologist and curator of birds at the Smithsonian National Museum of Natural History where his research focuses on the ecology, biogeography, and evolution of birds. His early childhood fascination with birds led to graduate studies at Louisiana State University and Florida State University: "I am unapologetically curious about natural history and the ways that natural history observations catalyze important ecological and evolutionary discoveries." His dissertation work focused on speciation of birds in the Andes Mountains of Peru. He has also conducted fieldwork in Brazil, Ecuador, Panama, Colombia, Polynesia, Canada, and in more than half the states in the USA. His current research efforts are split between the analysis of complex data sets based on the collective resources of the World's great museums and conducting field research in Jamaica, the great forests of the eastern USA, and in the Sonoran Desert.

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This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Snowy owl (Bubo scandiacus)
Courtesy of Martin Mecnarowski (, via Wikimedia Commons, BY-SA


About Owls (Order Strigiformes): Feeding

Owls are expert night hunters of birds, lizards, insects, mice, or even fish. Various adaptations make them skillful at catching prey in low light. The feathers across the front of their faces are flattened into a disk, surrounded by a fluffy ruff, which channels sound toward the ears. In many owls, uneven placement of the ears on their skull allows them to pinpoint the location of sounds with extreme accuracy. Owl eyes have extra light-sensing cells (rods) packing into tubular eyeballs that extend back into their heads. The eyeballs cannot move in their sockets, but owls instead swivel their necks more than 180 degrees to see what is behind them. Fringed, soft feathers on their wingtips act as mufflers, making for silent flight as owls sneak up on prey. Owls regurgitate parts of their meals, spitting out a pellet made of fur, feathers, bones, or other indigestible body parts.

Malachite Sunbird (Nectarinia famosa) feeding on flower nectar
Courtesy of Steve Garvie from Dunfermline, Fife, Scotland, via Wikimedia, CC-BY


About Birds (Class Aves): Feeding

All modern birds have bills and no teeth. The shape of a bird's bill says a lot about what it eats, for example whether it specializes in seeds (stout , cracking bill), fish (pointy, spearing bill), or plants (wide, serrated bill). Birds swallow their food without chewing, so it travels to the stomach whole or in large pieces. Bird digestive tracts have some special features for digesting chunky food. A pouch in their throat (the crop), is used to store food to be digested later, or regurgitated to feed the young. An extra, muscular stomach (the gizzard) grinds food up. Birds are endotherms, using heat they make internally to keep warm. While a few species allow their body temperature to drop at night (torpor), a nearly constant body temperature is maintained by most birds most of the time. Continuously making heat requires fuel to burn, in the form of food. So, birds spend a lot of time eating.