Mystery Tree - Backyard Variety

Some kind of Cottonwood with multiple trunks shooting out of the ground like an other-worldly plant form. The acorn-like nuts are driving the squirrels wild. They're up in this tree all day, flouncing about, feasting, then burying the excess all over the yard. Last year I saw a squirrel dig a hole in our lawn with his paws, drop a nut in, cover it with dirt, then place a leaf on top. Either a very paranoid action or a genius action. That squirrel impressed me.