Yes it is Ukrainian

and despite the fact the song is long there are very few words there. THat is very typical for Katya Chili. Here you have
Ой петрівняя зозуленько, ой!
Oh cuckoo bird, oh (she refers to the bird which is singing on a particular day it is a relligious holiday if I am not mistaking)
Та не літай рано по діброві, ой!
Dont flit in the grove in the morning
Такая... молодая...
Soo.... young
Та не куй рано по діброві, ой!
And dont say cuckoo in the grove in the moorning, oh!!
Не збуди мене, мене молодої, ой!
Dont wake the young me up, oh
Бо єсть у мене кращі тебе, ой!
Because I have better than you, oh
Що збудять мене раніш тебе, ой!
Who will wake me up earlier than you, oh
Молодая! молода-я! молодая!
Young! I am young !! Young!
If you are interest here is link for one of my favourite song of ukrainian I think hip hop band Tartak featuring Katya Chili, it was VEeeeeery popular one time(few years ago) because of her very unique voiece.
http://youtube.com/watch?v=5toIk5qO7nA
Enjoy!!