If an American friend is sending a birthday gift to myself in Canada,
will i have to pay duty on the gift?

Dear Rajab, 

Your friend must write clearly on the package that it is a gift. Then,
if it is worth less than $60 CAN, you will not have to pay duties:

"For an item to qualify as a "gift", another person must send it to
you personally and must include a card or other notice indicating that
it's a gift.

- If you receive an imported gift by mail and it's worth $60 CAN or
less, you don't have to pay duty or tax.

- If the gift is worth more than $60, you must pay duty and tax on the
amount over $60 CAN.
For example, if a relative sends you a gift worth $200 CAN, you must
pay the applicable duty, the GST or HST, and any PST on $140 CAN."

(SOURCE: Canada Border Services Agency, "Postal Program -- Duty-free
and tax-exempt importations",
<http://www.cbsa-asfc.gc.ca/import/courier/postal/ind_duty_free-e.html>).

I hope this answers your question. Please contact me if you need any
clarification on this answer before you rate it. My search terms:
canadian customs gifts

As I recall, the US is more generous on the dollar amount. I suspect
Canada has an exemption for antiques, much as does the US, which makes
the giving of an  antique more sensible when sending it across the
international border.