[Orgmode] Using capture to add plain text under a headline

[Axis]

Hello,

I'm having a struggle capturing a plain text item under a headline; it 
always gets added to the bottom of the file. List items or org entries 
can be stowed away properly without a problem, i.e.

("e" "Event" entry (file+headline "~/org/agenda.org" "Events") "* %? %^T")

works but

("b" "Birthdays" plain (file+headline "~/org/agenda.org" "Birthdays") 
"%\\%(diary-anniversary %? mm dd yy) turns %d")

doesn't.

Any clues as to what might go wrong here or how else I could add a line 
of plain text to a headline?

Thanks,
 Toby