On the website http://paizo.com/pathfinderRPG/prd/monsters/familiar.html the raven is listed as having a Perception of +6 in one place and a Perception of +3 in another. Which is it?
Ravens, for a time, were also erroneously given Skill Focus (Perception). When this was removed, it seems to have lowered the skill bonus to +3. So, the perception is still incorrect. Just for a different reason now.
Since we're talking about familiars, remember that familiars share their master's skill ranks. So, if the master has more ranks than 1, then the raven's Perception will be higher.