First time to notice this kind of birds in my area! I spotted them eating insects, especially large wasps! I suggest them to be Martins?!
I noticed it in between some plants and flower pots on my window, and kept seeing it at about the same place everyday for over a week! It wasn’t afraid of me, and even allowed me to carry it on my fingers and hand while watering the plants, when I then put it back in place thereafter!