The Eurasian eagle-owl is one of the largest owls in the world, and a Los Angeles Zoo page says Eurasian eagle-owls are the world's heaviest owls. Animal Diversity Web lists adult mass as 1,600 to 4,200 grams, with an average of 2,800 grams. It lists length as 58 to 71 centimeters, with an average of 65 centimeters, and wingspan as 1.5 to 2 meters.

Eagle-owls are mostly active in the first few hours after sunset and the last few hours before sunrise. An eagle-owl uses keen eyesight and hearing to find prey at night. The feathers around its face form a disk that helps direct sound to its ears. A Scottish safari park page says its hearing is so good that it can detect prey in the undergrowth from 75 feet away, but that figure is one park's statement. Its wing feathers are shaped to make little noise, so it can fly quietly toward its prey.

Eagle-owls eat many kinds of animals, from beetles to fawns, and they also eat birds, reptiles, amphibians and fish. An eagle-owl coughs up an owl pellet: a small ball of hair, feathers and bones it could not digest. Owl pellets are very useful to scientists because they help them understand what these hard-to-find birds eat.

Eagle-owls are largely solitary except when pairing up to breed. Animal Diversity Web gives a territory size range of 15 to 80 square kilometers, with an average of 42.5. Eagle-owls prefer to stay in the same territory unless food shortages force them to leave.

Eagle-owls do not build a nest. They use ledges, caves, and the old nests of other large birds. A pair has one to four eggs at a time. The female sits on the eggs for a little over a month, up to about 36 days, and the male brings food to the nest. Young eagle-owls hatch white and fluffy. They can feed themselves at the nest at about three weeks and can fly by about seven weeks old. Then they usually stay in their parents' territory for another 3 to 4 months before looking for a territory of their own.

Words to know

• mass: how heavy
• territory: an animal's area
• pellet: coughed-up ball
• solitary: mostly alone