Southern Cassowary, Casuarius casuarius. July 2010, Queensland, Australia.
Cassowaries are enormous like a velociraptor. This one made an amazing low-pitched boom that I liked very much. A workman came by with a pitchfork and it became very agitated and attacked the fence, also much like a velociraptor. Later on I fed it a little bit of mango.
According to wikipedia, the head crest is called a "casque" and is soft and spongy. One of the competing theories for its function is from article by Crome and Moore, which says that the birds lower their heads when they are running "full tilt through the vegetation, brushing saplings aside and occasionally careening into small trees. The casque would help protect the skull from such collisions."