They may not be exact synonyms of each other but what matters is whether they are both reasonable translations for the Finnish word kaunis. Even "nice" might fall within that range. Finnish and English words are rarely going to be exact one-to-one matches and it is useful if a range of words are accepted.
This is a beautiful parakeet = Tämä on kaunis undulaatti
This parakeet is beautiful = Tämä undulaatti on kaunis
In the first one you're emphasising: TÄMÄ on kaunis undulaatti. (THIS is a beautiful parakeet.) For example you're pointing a picture with many animals
In the second one you're emphasising: Tämä undulaatti on KAUNIS. (This parakeet is BEAUTIFUL.) You're pointing to the fact that it is beautiful. It might be a new fact.
Parakeet is actually a family of over a hundred different species of parrots. The animal referred to here, undulaatti (Melopsittacus undulatus), is actually budgerigar in English, but in American English it's usually just called parakeet.
Undulaatti originates from Australia and they're very popular pets especially in Europe and North America.