Birthday set for a contact in Google is not syncing with BusyContacts
Unfortunately, Google does not sync the Birthday field with 3rd party apps, and so this won't sync back to BusyContacts.
However, you will need to manually make this change in each of your contacts in BusyContacts and this should in fact sync back to Google Contacts.
Open Preferences in BusyContacts > Info Panel and then from the "Show Field" drop down, select the "Date" field. Now click on the Date field that shows up in the preview contact card, and select "birthday".
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