Thanks to my friend Bill Sherwonit (Letters, Feb. 10) for clarifying the percentage of birds killed by cats in the U.S.  Based on the figures he gives, the daily kill works out to to about .45 percent (point-four-five) of the average U.S. bird population.  I’m not sure I find that unacceptable.  Bird populations seem to sustain themselves at that level of predation, on top of their natural mortality,

And what about the 12.5 billion tiny mammals killed annually by cats?  Say for argument’s sake the mouse/shrew/squirrel predation rates are the same as for birds.  I’m not sure I would welcome a 16 percent annual increase in the tiny mammal population if all cats were kept inside.  Don’t biologists have an expression — “an explosion of voles?”

— Diane Pleninger

Anchorage