Yellowknife NWT Canada   Temperature -30  Wind speed 40-50km/hr
Ravens playing on updrafts....for hours at a time.... why do they not
freeze their eyes?

I don't know whether this is true of ravens, but many birds have a
transparent nictitating membrane which is like an extra eyelid. It
protects the eyes from wind and/or water, while allowing the bird to
see.

The structural and functional features of antifreeze proteins (AFPs)
enable them to protect living organisms by depressing freezing
temperatures, modifying or suppressing ice crystal growth, inhibiting
ice recrystallization, and protecting cell membranes from cold-induced
damage. The versatility of the AFPs suggests that their production and
commercialization would be a potentially profitable venture.

AFPs and their genes can be used in fish and plants to enhance
resistance to freezing. AFPs can be used in medicine to improve the
cold protection of blood platelets (to extend their shelf life prior
to transfusion); paradoxically, when used in conjunction with
cryosurgery, they can help destroy malignant tumors. Their ability to
inhibit recrystallization can improve the quality of frozen foods. In
addition, antifreeze gene promoters are uniquely suited to drive the
expression of functional genes, such as growth hormone that results in
enhanced growth rates of salmonids (e.g., salmon, trout) and other
fish species valuable to aquaculture.
check this article
http://pubs.acs.org/hotartcl/chemtech/99/jun/fletcher.html

The answer is that the eye gets a large amount of blood flow and since
the blood is warm, it keeps the eye just warm enough to keep it from
freezing.