Birch tree juice drinking and harvesting is an old tradition in Russia. The main season for this fun is spring. Tens thousands of birch trees across the country become the source for this delightful liquid, harvested mainly by kids.
Usually there are two methods of doing this. One is to make a hole in the tree body itself then put some kind of straw or pipe in the hole connected with some bottle. Usually the big wine bottle gets full of the birch tree juice from one tree overnight. Another way is to brake a branch and just insert the branch into the bottle, then tie or tape the bottle to the branch.
Russian expatriates abroad are often ask local groceries for bottled juice and very surprised when can't get it.
Sometimes, when the spring nights are freezing, one can see his harvest place turned into this state as on those photos. Then he gets a frozen birch juice.