This is a strange experience. I have an office with a window on the second floor of a building, and there are trees outside. I heard a thump on the window, and when I looked over I saw a robin bird sitting in the tree. About a minute later, the robin bird flies into my window. I've been in this office for a long time, and robin bird or any bird for that matter has never done that before.

Then, another robin bird came over and sat next to the first robin bird. The first robin bird takes off and flies into my window again. The other robin bird just watches. The first robin bird does this a couple more times, then they both fly off.

What is going on? It's a cold foggy day here, so it's not like this is spring weather. Why would a robin bird try to fly into my window over and over again?