Q:

How do I get my google contact's birthdays to show up in evolution calendar?

I have synced evolution to my google calendar and google contacts. That went well.
But why can't I edit any of my contact's birthdays in evolution? And why are those birthdays not displayed in evolution's calendar? The birthdays are present in the webcalendar of google.
Edit: I had allready tried the method suggested by Kory Wnuk in one of the answers below. For some reason I can't click okay in that dialog:

A:

Just for completeness:
Purging Evolution and starting all over again helped my "okay is not clickable" problem. No idea why the okay bug occurred in the first place - I had tried at least ten times on different days with no success. 
Then I was able to add the birthdays calendar from google to my evolution. Adding was done using the method in the picture of my original question.
Sill a feature in evolution would be nice, that allows editing birthdays in google contacts.

