Why are crows so smart?

Sample Causal Analysis: Why Are Crows So Smart?
Directions: Watch the PBS Nature documentary embedded below.  It looks at some of the reasons why crows are the smartest birds on earth. In other words, it’s an example of a causal analysis argument.
Then submit your answers to the following questions by Thursday, October 14th:  

 Have you ever observed crows engaged in an activity which demonstrated their intelligence? Share your anecdote.
The video mentioned several of the negative effects that can occur in human society as a result of crow intelligence. Name one of these and then list one you can think of on your own.
The video mentioned several reasons why crows developed their advanced intelligence.  Bullet a list of these.
Crows are often thought of as pests or presented as sinister in film. Did watching this video change your impression of crows? If so, then how and why? If not, then why not?