"We see birds."
ODD... I skipped this one and it said the correct answer was "Vemos aves". i didn't learn that word for birds...
What would be the difference if we wrote, "Nos vemos pajaros?" Sometimes the "nos" is redundant and sometimes it is not. In this case, I still got it correct, I just don't know when it's needed and when it's not.
Los pajaros was marked wrong. I still can not grasp when i must have article and when i must not.
Sometimes Duo is amazingly lenient on typos, sometime they want 100% compliance ;)