In this photo, a snowy owl takes off from a tree at sunset. I had been watching it for over an hour. The moment is exciting. As the zoomed-in photo shows, these are heavy birds with big wingspans. Their abundance of insulating feathers is part of the reason for their weight. Even their feet are covered in feathers. They are built for the cold. These birds can weigh up to 6 pounds and their wingspan can be up to six feet! 

Interestingly, snowy owls head south about every four years or so. They call this phenomena “irruption”.  Lately, irruptions have been more frequent. It is believed they do this for food, rather than for breeding. Snowy owls are actually the northernmost breeding raptor in the world. So why are these “irruptions” happening sporadically? Scientists believe it has to do with populations of lemming in the tundra. Lemming are small rodents, similar to muskrats. Summers with big lemming populations in the tundra have been found to translate to large irruption behaviors in the winter. A single snowy owl can eat 1,600 lemmings a year! The clutch size of snowy owls, the number of eggs they lay at a time, is determined by the amount of food available in their environment. With low years, snowy owls may only lay three eggs, but in high years snowy owls may lay eight eggs. Those baby owls grow up into adults, and now there is competition in the neighborhood. This is why scientists believe more snowy owls are heading south, to avoid the competition.