Birds from my yard keep pecking/flapping trying to get into my windows at night! Its creepy, what's going on?

There are many songbirds in my yard, recently there have been some pecking and flapping against my windows at night when Im watching TV. It is even happening in the middle of the night, when these birds should be asleep! They are just normal yard birds, such as robins and small finches. They are not migrating, and have residency in my yard and surrounding area. I found a dead one on the porch a few days ago. I've had them hit the windows before, but this is as if they are trying to get inside the house at night! What is going on, and what should I do?