I would sure like to know what the blue jays are saying to each other. Sometimes I feel as if I'm watching a foreign film without the subtitles.

Such as when their heads bounce up and down, and they call like ringing bells. Still, sometimes I can catch the drift.

Dear Diane: A reader writes: There are a couple of woodpeckers at my feeders that I thought were male and female downy woodpeckers. How can I tell the difference between a downy and a hairy woodpecker? Their colors are identical.
-- John I., PA

You're not the first person to be fooled by these two cousins. But it's usually possible to tell them apart. The most obvious difference is size (hairy bigger than downy), but that can be hard to judge if you see one alone.

So to determine which species you're seeing, first look at the bill...

You sometimes see "twilight factor" listed in a binocular description, as a measure of the resolving power in dim light. It's a mathematical formula that can be misleading. The term was more important years ago, before modern optical coatings were invented, than it is today.

Photo of two great horned owls is a PGC Photo, copyright Hal Korber.
The blue jay photo is copyright Michael and Diane Porter.