Could someone please explain why Hawkman in Kingdom Come has an animal head, rather than the normal human head and mask?

Thanks!

There isn't really an explanation. In Kingdom Come, you have more modern interpretations of classic characters. For instance, there's also no explanation of why the Green Lantern from that story, who is identified as being Allan Scott, has the emblems and trappings of Hal Jordan.
That version of Hawkman has the bird head because it made a good design.

It could have been, what was his name, Northwind or something like that...

Northwind came after Kingdom Come.

http://en.wikipedia.org/wiki/Northwind_%28comics%29

Northwind debuted in the 80s.

I belive it is supposed to represent the Hawkgod itself taking human form

Because Alex Ross thought it looked cool.

He poops on newspaper.