Complex sentence: Over 250 species of birds inhabit the lake area, 61 of which are endangered in Bulgaria and 9 globally, attracting keen birdwatchers from all over the world; the lakes are also home to important fish and invertebrates.
Split into simpler sentences: Over 250 species of birds inhabit the lake area, 61 of which are endangered in Bulgaria and 9 globally, attracting keen birdwatchers from all over the world. The lakes are also home to important fish and invertebrates.