Hawk in Costa Rica

I photographed this hawk near Cahuita National Park in Costa Rica in December 2007.  The guide identified it as a chicken hawk - which I understand is a general term for any hawk that preys on chicken.  Looking through the books I have at home, I thought it might be a common black hawk or maybe a zone-tailed hawk.  Your thoughts would be appreciated.

Source: http://www.whatbird.com/forums/forums/thread/22196.aspx