Oracle Text

Move any number of +1/+1 counters from target creature onto another target creature with the same controller.

Card Rulings

1/24/2013 To move a counter from one creature to another, the counter is removed from the first creature and placed on the second. Any abilities that care about a counter being removed or placed on a creature will apply.
1/24/2013 You decide how many counters to move when Bioshift resolves.
1/24/2013 If one of the two creatures is an illegal target when Bioshift tries to resolve, or if the creatures are controlled by different players at that time, no counters will move.