Return of the Ruby-throated Hummingbirds

If you've not done so already, it's time to clean out and refill your hummingbird feeders, because the Ruby-throated hummingbird - the king of nature's frequent flyers - is on its way back to the eastern U.S. Reportedly, they are about a week ahead of last year.

Ruby-throated hummingbirds spend the winter in Central America, roughly between southern Mexico and northern Panama, and begin leaving in January. The males leave first, followed about ten days later by the females, but their exit from Central America is spread over a three months period, and they do not migrate in flocks. These factors eliminate the possibility of losing the species to storms.

Some will take the long route over land, hugging the coast of the Gulf of Mexico. Others will take the over-water route, landing in North America from Texas to the Florida panhandle. The 500-odd mile flight takes about 20 hours, and the birds may lose half of their pre-migration weight.

Once in North America, the birds move steadily northwards, covering about twenty miles per day. Banding studies have indicated that the birds tend to return to where they hatched.

By mid-July, the southward migration has begun, but the peak southward migration occurs when flowers stop blooming and insects become more scarce. Also, Ruby-throats are less tolerant of cold weather than other hummingbird species. The peak migration is from mid-August through mid-September. By late September, the birds you see at your feeders are migrating birds, and probably not the birds you enjoyed during the summer. Since they all look alike, it is impossible to tell which is which. The number of birds migrating south is much higher because of the young birds joining the flight for the first time.

Since Ruby-throats don't migrate in a flock, it is unclear how the young birds know where to go. Apparently something instinctively tells them, "It's time to go," and they use an inherent form of dead reckoning navigation to find their winter habitat. Banding studies indicate that once a young bird completes the first southern migration, it will use that same route for each southern migration for the rest of its life. If it works, why change? And again, the males leave first.

Most Ruby-throats take a land route back to Central America, even if they crossed the Gulf on their northern migration earlier in the year. Perhaps hurricanes in the Gulf have reduced the number of southerly migrating Gulf-crossers to a small minority.

But why go to all the trouble? Why do they migrate? You have to think back to the last ice age for the answer. As the ice covering most of North America retreated, some tropical birds discovered there was less competition for food and shelter if they moved northward, following the retreating ice. Some song birds could survive the colder climate, eating berries and seeds when insects were no longer available. They're the birds we enjoy year round. The Ruby-throats, however, are carnivorous and must rely on nectar of flowering plants and insects. Hence, they must make the long journey south to find food.

Yet not all Ruby-throats go all the way to Central America. A few spend the winter on the Gulf coast, and a few "winter" on the Outer Banks. Perhaps they are too old or ill to make the crossing. Or maybe they were hatched too late to put on enough fat. So, their survival depends on a mild winter.

The good news is that the "Platinum Medallion" of frequent flyers is on its way back. Welcome them with a clean feeder filled with fresh sugar water, so they can regain their energy for the mating season.

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