Birds vary quite a bit, many are susceptible to frostbite on the toes. Many common tropical zoo species are not really hardy below 40-50 F, even with heat. American Flamingo is one that can be outdoors in fairly cold weather, Blue Cranes and kookaburra as well. Quite a few tropical waterfowl species can tolerate below freezing temps if they have access to open, moving water. Ostrich, rhea, and cassowary are somewhat tolerant, but their plumage tends to hold water and cause hypothermia. They also are prone to slipping on ice and cannot be allowed outdoor access in icy conditions. Given many bird parks are in colder locations (Sylvan Heights, Walsrode), some are definitely likely able to tolerate cold temperatures if acclimated well and provided heat.
Far as hoofstock, quite a few are tolerant of cold temperatures if acclimated and provided unrestricted access to heated shelter; Addax, African Buffalo, Common Eland, Gaur, Grant's Gazelle, Grevy's Zebra, Impala, Klipspringer, Nyala, Plains Zebra, Roan, Sable, Scimitar-horned Oryx, Sitatunga, Somali Wild Ass, Springbok, Thomson's Gazelle, and Waterbuck are among these. Obviously varying conditions such as ice, storms, and heavy snow complicate things, and both young and old individuals generally should not be allowed out in below/near freezing conditions.
Most subtropical/tropical primates are typically not cold hardy, there are occasional limited exposure/successes with appropriate holding and heating. Most primates are not recommended to be allowed any outdoor access below freezing; most species it is recommended to not allow them out under 50 F or so.