Please help make penguin white background transparent but not penguin's chest

view story

http://ubuntuforums.org – I'm using Gimp 2.8 and I have the GNU Penguin image on a white background, which I want to make transparent, while keeping the penguin (including his white chest) entirely opaque. I tried following this thread (post #4) but when I got to the bit where it said: Quote: Drag black color on to the image to "bucket fill" the selected areas with black color. Since the layer mask (not the actual image) was selected, the black color will be painted on the layer mask. Nothing happened at all, the black colour was not painted on the mask. The thread was a 20 (Hardware)