Hi @James_Wales - you can use a formula field to show the birthday this year:
DATETIME_DIFF(TODAY(), Birthday, 'years'),
This gets the number of years between the birthday and “today” then adds this number of years to the birthday. As an aside, this deals with birthdays on 29th Feb and these are forwarded to the 28th Feb.
Now that you have the date for this year, you can use this in an automation to send an email. Something like “when birthday this year = today”.