In the following question, a sentence is divided into four parts (P,Q,R,S). Rearrange it in the proper sequence in order to make a meaningful sentence.
P: known bird species are declining in numbers, and
Q: approximately 70% of the world's nearly 10,000
R: roughly one of every eight (12%) of these bird species is threatened with extinction
S: mostly because of habitat loss, degradation, and fragmentation