I have the following Wikipedia API search query:
http://en.wikipedia.org/w/api.php?&action=query&generator=search&gsrnamespace=0&gsrlimit=20&prop=pag
My workaround for now is to filter search results server-side, by only showing articles that have birth_date in their revision content.
birth_date
The bounty is still available if someone finds a way around this.