SWARM OR MIGRATION?

Since its winter there are a lot of changes not just for us humans but also for animals. Some animals hybernate and some migrate to other warmer climate. Just about 2 hours ago MIL called me in the family room and pointed outside the deck and out backyard. The backyard was swarming with black birds and so were the trees. It was everywhere not just in our backyard but also our nieghbours. It was kind of scary since you see horror movies that birds swarm and they kill. The birds would fly off and then land on the ground, trees or rooftop again and again. It was like they were in separate groups. The first group would land and eat for a minute then they would take off to the sky then the next bacth would land again. That went on for about 5 minutes. I got scared thinking it was a bad sign or a omen of some sort then i got to thinking, that its already winter so the birds are probably starting to migrate. It was
beautiful to watch but scary, it gave me goosebumps. It was my first time to see birds that many. the three lights you see in the pictures is not flying saucer or alien craft but the reflection of out lights on the glass door.