What is that bird in the backyard?

Question

It's between dove- and duck-sized, has a light gray body and dark gray feathers, and a brown head. It's feathers stick out behind its body, and end in a point. Someone said that it might be a quail, but it doesn't have that familiar little doo-hickey on its head. We live in Illinois. On top of that, it's been sitting in the same spot for a while, occasionally bending down to peck at the ground.

It has long, feathery legs, and he appears to be a plant-eater.

It's body and feathers have stripes on them.

Seems vicious, tearing at leaves or something while holding it in its feet.
The feathers on his legs are white.

Answer 1

The feathery legs would indicate some species of grouse, sharp tailed, ruffed or spruce grouse would be my guesses for your area.
Ptarmigans have feathery legs as well but would not be that far south normally.

Answer 2

My best guess is

Gray Partridge:
http://www.pbase.com/grahamcheckley/image/71188050

Answer 3

Is it possible to get a picture of it, and post a link to that here? It is so much easier to identify a bird from a photo than from a description.

If not, could you also tell us a few more things? What is the shape of its beak? Is it shaped like a duck's bill? A cardinal's beak? A chicken's beak? And what about its feet? You mentioned feathers on the legs - what about the shape of the feet?

I suspect it may be a hawk, not tearing at the vegetation, but at a bird or mammal it killed and is eating.

Look at these links and see if anything looks like your backyard visitor:

Prairie falcon: http://www.enature.com/fieldguides/detail.asp?source=&parkid=&searchText=&allSpecies=&shapeID=958&lshapeID=0&curAbbr=&lastView=default&lastGroup=1&lastRegion=2205&lastFilter=4&lastShapeName=&trackType=&curRegionID=2205&size=&habitat=&fruit=&color=&sortBy=family&curFamilyID=®ionSelect=Great+Lakes®ionZIP=&curGroupID=1&lgfromWhere=&curPageNum=18

Peregrine falcon: http://www.enature.com/fieldguides/detail.asp?source=&parkid=&searchText=&allSpecies=&shapeID=958&lshapeID=0&curAbbr=&lastView=default&lastGroup=1&lastRegion=2205&lastFilter=4&lastShapeName=&trackType=&curRegionID=2205&size=&habitat=&fruit=&color=&sortBy=family&curFamilyID=®ionSelect=Great+Lakes®ionZIP=&curGroupID=1&lgfromWhere=&curPageNum=19

Gyrfalcon: http://www.enature.com/fieldguides/detail.asp?source=&parkid=&searchText=&allSpecies=&shapeID=958&lshapeID=0&curAbbr=&lastView=default&lastGroup=1&lastRegion=2205&lastFilter=4&lastShapeName=&trackType=&curRegionID=2205&size=&habitat=&fruit=&color=&sortBy=family&curFamilyID=®ionSelect=Great+Lakes®ionZIP=&curGroupID=1&lgfromWhere=&curPageNum=20

Answer 4

It's an American Ducky-Doved Doo-Hickey. (The little doo-hickey will reveal itself at about age 4.)

Answer 5

A photo would be really helpful. I'm not really sure what you are seeing.