I have often had cause to retrieve injured birds over the years. In almost every case they screech when I pick them up. Is this because A: They're terrified. B: They're hoping to startle the predator (me) enough to give them a chance to escape. C: They're hoping to attract help from mate or parent. D: They're trying to warn others of their species. Or is there an E?

I went to check the cistern-operated water supply to my domestic ducks a couple of weeks agao, and found a small plastic cap floating in it. I took it out, but the next day it was back in. This time I threw it a couple of metres away. The next day it was back in again, and has been redeposited there every day since. Why are the ducks doing this? Also, why do they spend so much of their time deliberately muddying their water supply?