Mice, birds and knowing (spoilers)

Like many fans of this film, I've been baffled by the scenes with M. Hire dropping a dead mouse into the water, releasing the mice on railway tracks - and feeding birds and then talking about a bird poisoner.
Was his intent to kill birds and mice - or was he simply feeding and releasing them?
Watching the film again I found the mystery about the animals echoed a main theme of M. Hire - you can see some of the things a person does but that doesn't mean you totally understand what drives them. When Alice first confronts M. Hire, he tells her "But you don't know me."
Not knowing a person's motivations - kindness or cruelty - of course totally mirrors the entire relationship between Hire and Alice. She appears so very nice but she is the one in control and ultimately her guile leads to his death.
Of course this isn't the only explanation for the symbolism of the mice and birds but I think it's a reasonable one.