In going through the identification lookups here online, I thought it also might be a green heron based on looks, however, in listening to various calls online, it doesn't seem to be a match with the single call that we're hearing. They make this only one call, and at only an interval of between 1-2 minutes between calls. I know nothing of green herons, but the online calls would lead me to believe them to be a bit more noisy, higher pitched and energetic?
The actual sound is also a bit more 'Bassy' in person than what was recorded on my camera's audio capture. Almost sound a bit reptilian, if that makes any sense.
Blue Heron Calls:
http://www.allaboutbirds.org/guide/Green_Heron/sounds
http://identify.whatbird.com/obj/32/overview/Green_Heron.aspx
