Comma and where

I found some sentence when I was reading online newspaper about flamingos;

"They also live in Argentina, Bolivia and Ecuador where they reside mainly on estuaries, lagoons, mud flats and salt lakes."

I understood like this: They also live in Argentina, Bolivia and Ecuador. and in the countries they resides mainly on estuaries, lagoons, mud flats and salt lakes.

Am I wrong, or did the writer forget to put in a comma before "where"?

I want to know your opinions.