August is a special month for both ruby-throated hummingbirds and those of us that enjoy watching them.  Throughout the entire month, the number of hummingbirds visiting our feeder swells as they voraciously feed on the nectar provided by our feeders and flowers.  The reason for this increased activity is these flying jewels must quickly eat enough food to enable them to store the fat required to fuel their long journey to their winter home.

       In order to accomplish this task, hummingbirds make frequent feeding forays to our feeders and as many flowers as possible.  Since hummingbirds have one the highest rates of metabolism known, they expend huge amounts of energy trying to prepare for their arduous migration.  Obviously, anything that makes this task more efficient greatly benefits these flying dynamos.

       One way the birds would be able to streamline their feeding binge would be to possess the ability to avoid visiting flowers that harbor little or no nectar.  Well, as amazing as it may seem, they can do just that.  Here is how it works.

       The amount of nectar produced by each nectar plant varies considerably throughout the day.  A number of variables such as soil moisture and weather conditions affect it.  When hummingbirds, butterflies, bees, wasps, and other nectar feeders consume nectar, it takes time for it to be replenished.  This time varies considerably.  For example, some flowers do so only once a day, others every half-hour, others varying amounts of time in between.

      Ruby-throated hummingbirds have the ability to learn how long it takes a flower to rejuvenate its supply of energy-rich nectar.  Consequently, when a rubythroat visits the zinnias, salvias, lantanas, bee balms, trumpet creepers, and the like growing in our hummingbird gardens they rapidly learn how long it takes each plant to produce a new crop of nectar.  Only then will they revisit a plant it fed at earlier in the day.  This eliminates the need to revisit the plant until correct amount of time has elapsed.

       This astounding ability has been demonstrated by researchers such as a team of University of Edinburg biologists.  Their experiments involved providing hummingbirds with two groups of artificial flowers laden with nectar.  One group of flowers was refilled with nectar every ten minutes.  The second group was replenished every 20 minutes.  In short order, the hummers learned when each group of flowers provided them with a source of food.

       Keep this in mind as you watch the hummingbirds visiting various flowers about your yard.  It will help you better understand why they feed at certain nectar plants when they do.  If you are like me, you will come away being even more impressed with a bird so small, ten could be mailed for the price of a first-class letter.