You have heard the expression “wolf in sheep’s clothing”? With the Great Grey Owl, it is more a case of “little owl in big owl clothing.” Though this owl is the largest owl in North America – measuring about 2 feet tall (61 cm) – it weighs only 2-4 pounds (0.9 - 1.8 kg). Compare that with a Eurasian Eagle-owl, which is just slightly larger, but weighs 3-9 pounds (1.4 - 4.0 kg) and you will see what we mean. Why is this so? Great Grey Owls have relatively small bodies but are covered in so many dense layers of long feathers that they appear to be much bulkier than they are. It would be like you wearing all your clothes at once, which would definitely make you look much bigger. One advantage to this could be protective – a large appearance can be deceiving to predators and make them think twice before attacking such large prey.
From the Peregrine Fund: