Ruby-throated hummingbirds are a joy to watch. These tiny birds burn up so much energy they're forced to eat almost constantly, and keep right on feeding into twilight after most birds have begun roosting for the night.

A major portion of their diet is sugar derived from flower nectar and tree sap; protein comes from ingesting small insects.

Being inquisitive, ruby-throats will swoop down to investigate red articles of clothing and are easily attracted to feeders with red parts.

Fill a feeder with a dissolved mixture of one part white sugar to four of water, but do not add food coloring.

Minnesota's smallest bird, the migratory ruby-throated hummingbird ranges from 3 to 3.5 inches long with an average weight of 3.4 grams (it would take 133 to equal 1 pound).

The bird's appearance is unmistakable — metallic green above and white below. It gets its name from the ruby throat of the male. They are with us from May through September, and nest from June into July.

Survival for a hummingbird depends on fast movements, and courage. They can hover, move backward, and dart forward at high speed to outmaneuver other birds.

Being aggressive in defense of territory, they will go after much larger birds such as crows and blue jays, using their long needle-sharp bill as a dagger.

Jim Gilbert's observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He teaches in the Environmental Studies Program at Gustavus Adolphus College.