are you aware that panama's christmas bird count has one of the highest species count of any in the world, if not the highest? there is a beautiful resort called gamboa resort near the soberania (spelling?) national park and the famous pipeline road
you could potentially see hundreds of bird species, both tropicals and winter visitors from the united states and canada
it is not like banff -- a beautiful place but a BIG wildlife place, there will be no elk or bear, but there is a richness of smallest wildlife such as the colorful birds, parrots, caimans, slothes, lizards, and a very pleasant temperatore
malaria medication and shots are not required for the canal zone of panama, and the people are super friendly
i loved it, wish i could move there! good roads too, unlike costa rica, which would be another choice pick
there is even a rainforest park in panama city itself!
wonderful place
oh, and december is part of the panama "summer" too, their seasons don't work like ours, their "winter" is rainy season (around june), december is dry
and no jet lag, unlike the new zealand suggestion, altho i'm sure new zealand is super cool too
good fishing too if you like fishing
here is the website for gamboa resort, there are also less expensive options:
http://www.gamboaresort.com/principal2.htmoh, and also the famous canopy tower, the old radar station, but you really need to book in advance for that one!
it is possible it would all be booked by the bird tours at that time of year but here is their link--
http://canopytower.com/toucans aplenty! i say go for it! i'm a budget traveler so i haven't been able to visit these during the prime christmas season, rather i visit off-season, but one day it will happen