How to import Facebook Birthdays to get merge with Android Contacts?
If you sync your contacts with Google than you can add a special calendar. That you can only do on the web interface. 


Select Settings | Calendar settings in Google Calendar. 
Go to the Calendars tab. 
Follow the Browse interesting calendars » link under Other Calendars. 
Open the More tab. 
Click Subscribe for Contacts' birthdays and events.


Now after syncing the events will show up in the calendar app.