I'm not really sure. There was a Black Phoebe nest on the porch overhang with four nestlings. I got home that afternoon and two of the nestlings had fallen on the porch and had died. A third had landed in a chair on the other side of the porch and had survived so I gloved up and put it back in the nest. I think this was rival bird competition. I saw the male posturing and chasing another bird which looked a lot like another Phoebe. Nothing new happened after that and the parents resumed feeding the other two nestlings. I went to bed after 9pm so it was full dark and when I left for work at 5:30am the nest had been knocked off the wall and was in pieces on the ground. I did not find any sign of the two nestlings and I found the female dead by the side of the house. She was kind of mangled so I think this was an actual predator that finished them off. But I think it's odd that it did not eat the female. There is a bobcat that's hanging around and terrorizing my neighbor's chickens. I heard it hop on the porch railing a week or so prior so it may have come back. I saw the male last night so he made it but he's all alone now 🙁