In the beginning of the movie when Thor takes Loki from the Quinjet to the mountaintop you can briefly see two ravens flying in the vicinity. Though I have found no official confirmation I believe that the ravens are none other than Munin and Hugin.
In Norse mythology Munin, which is Old Norse for memory/mind, and Hugin, which means thought, are two ravens that fly all over Midgard obtaining information for the all-father Odin. The ravens can also be seen at the beginning of Thor at the coronation ceremony, they sit on Odin’s throne with one on each side.
To have the ravens in that particular scene, a scene where Thor comes face to face with the brother he thought lost is too much of coincidence to think that they are not Odin’s ravens.