Generally, the blackbird is a bad omen which forewarns of future losses and unhappy events to take place in the waking life of the person in whose dream these birds appear.
A blackbird appearing in your dream may also be an advice that you should strive harder to attain your goals and not give up whenever something unpredicted, such as a burden or obstacle, gets in your way towards success and prosperity. You are not using your full potential and all your resources to succeed in what you plan and want to achieve.
On the other hand, seeing a blackbird flying or singing in your dream may also bear a positive significance and foretell fortune and good luck.
If a blackbird appears in the dream of a woman the bird may announce the meeting with a new, agreeable person and if populates the dream of a man this foretells him a sudden sympathy with a woman.