Theme 20-20 is the last level for Blossom River. Here, you must defeat Nigel and his Marmosets from reaching the Amazon.
The level starts with three Yellow Birds, a White Bird, a Black Bird, and a Boomerang Bird. When the battle begins, the barricades will block Nigel from being destroyed. They will remain closed until all the Marmosets are defeated. If you have defeated all the Marmosets, the barricades will open and it is time to defeat Nigel. Use Matilda to reach Nigel and defeat her. This will push him to a fuse, which will destroy the entire boat.