I can't tell from the photo, what the black mass is on the head of the bird? Is it a swollen wound?
I try and think about how spiders interact with each other usually. I saw a jumping spider kill a recluse in the corner of my window. Since then I have been hesitant to kill them all, because I can't kill the ones I don't see...So I let nature take it's course with the spidey's. Unless it's directly threatening me, like the other day, and I don't have time to establish it's identity. lol! My husband was so scared he made me kill it. (croquet mallet)
Since the new puppy has been around, I might take a new course of action and kill them all, 'tis true....For the same reason. Now I'm not willing to let nature take it's course or I could end up with a sick puppy.
No wonder aussie's seem so tough.
