Angry Birds are not just tetchy for the sake of it. Now they're angry about endangered bird species - and they're doing something about it.
Rovio Entertainment Ltd, the Angry Birds creators, have joined with BirdLife International to support The BirdLife Preventing Extinctions Programme.
A new Angry Birds website helps 'the world's 189 angriest birds' - the birds that are critically endangered according to the N, International Union for Conservation of Nature (IUCN).
Angry Birds fans, and fans of birds in general, can play the game on the site to find out why these birds are angry at being endangered.
Donations to the programme are taken through the site, to support birds like the Phillipine bald eagle, Sociable lapwing, Northern bald ibis and the Fiji petrel.