A good strategy for Piglantis level 2-9 is to loft the Blue birds through the icy bridge between the second and third towers. At the least, the last tower should end up in the ocean, but perhaps you can manage a bit more. If only one tower is gone, use the Boomerang bird to detonate the TNT in the middle tower.
3-star Threshold Change: In the v2.5.0 (Back to School) update, the 3-star threshold for this level was raised from 100,000 to 102,000. We have asked Rovio whether this was an intentional and will report back if we get a reply. In any case, we have uploaded a new video that earns 3 stars no matter what, with a score of 103,940.
Bug Fix: The threshold has returned to 100,000.