Today, May 22, 2019, I heard a bird high up a tree calling her babies out of a blue bird house in my yard. I had never heard that kind of bird call; I didn't get close, for scaring the mother. After all the noise faded, I went to check the house and it was vacated. (About four or five months ago, I discovered the house was vacant but the entrance hole was greatly enlarged. I saw photos online of a similar hole in a bluebird house made by a squirrel. My yard abounds with squirrels.) The empty nest was made of pine needles, had some soft material and 2 feathers. One feather was about 1 and 1/2 in., white at the base, then beautifully rounded, light brown. The other was very unusual, about 5 inches long, with fluffy gray down at the base and then turning brown, with stiff inch long threads, tapering up to a point. What could this bird have been? I thought maybe a small-type owl, but shouldn't they be nocturnal? I'm so curious, my nose is about to fall off!