Just thinking, would the beans make winter food for birds ?
Would they be acceptable, say, dried and chopped or minced for the bird
table ?

I very much doubt it. If you do not believe that, try one or two for
yourself - they are quite toxic to humans and people have been known to die
after eating them. Perhaps if you eat a lot they'll make you so sick so
quickly that you will not die - but don't rely on it!

Are they toxic to birds? I do not know but their toxicity to humans is
destroyed on boiling for about 20 minutes I think.

Geoff