it says "A group of vultures is called a venue...Vultures circling in the air are a kettle."

I've heard of a wake of buzzards or vultures, W'ON. And a "viewing" would make more sense to me than a "venue", i.e. viewing in the sense of:

A watch over the body of a deceased person before burial, sometimes accompanied by festivity. Also called viewing.

Not saying the author of the article you are reading is wrong. "Kettle" just sounds a little 'fishy'. :)

http://snipurl.com/gsem

Oops! I stand corrected, W'ON. Your author is correct. A kettle is another name for a wake of vultures.

Groups of vultures spiraling upward to gain altitude are called "kettles". As vultures catch thermal updrafts they take on the appearance of water boiling in a pot – hence the name kettle. Turkey vultures have been reported by aircraft pilots to rise to as high as 20,000 feet and soar for hours without flapping their wings.

http://snipurl.com/gseq