C. Claiborne Ray

Chimney swifts in search of homes eventually may have to return to hollows in big, broken trees. But there probably aren’t enough of them.

In some species, individual animals can be distinguished by unique identifiers, not unlike human fingerprints.

Grapefruit trees need light, bees — and a temperature gradient.

Most dogs love to fetch. Some are obsessed with it.

In some species, youngsters play to develop skills they’ll need as adults. But in other animals, adults seem to frolic for the fun of it.

Frozen fish often loses its healthy color, even though it’s perfectly good. The culprit: ice crystals.

The rotation of the Earth forces winds into clockwise and counterclockwise motions, depending on air pressure.

It’s more efficient for tugboats to nudge barges along, but some conditions require that the loads be towed.

They don’t need sunlight because they are busy feeding on other organisms.

Introduced to Europe from the Americas, the common bean was cultivated into a staggering number of varieties.