How can I add a new search engine to Safari without any 3rd party add-ons? I know add-ons such as Glims can do this, but I would rather stay away from them.  Any native (or more likely semi-native) way to do so?  If it matters, the engine I would like to add is duckduckgo.
No, the only options are Google, Bing, and Yahoo.

If it is of any help, DuckDuckGo have their own extension on the Apple website for Safari extensions.