Snow

Snow, is a white and very soft material the Pigs use for their forts on Season's Greedings and Wreck the Halls along with Clouds, first appearing Hogs and Kisses and Sand from Angry Birds Rio. It is easily destroyed by any bird, and any bird can destroy any size of snow blocks. Unlike most materials pigs use, snow is not affected by gravity, and can hold things up in midair. If the snow is destroyed, however, holding a large portion of a structure, the entire section will come crashing down. Snow is also destroyed when an object too heavy for it falls onto it. If snow is damaged it appears with many ripples in it.

Trivia

 * Snow, along with Clouds and Sand are the softest breakable materials used for forts.