There is much we do not know about the ruby-throated hummingbird. For example, most of what we know about how high rubythroats fly when they are migrating is based on anecdotal evidence. With that in mind, it appears that ruby-throated hummingbirds migrate much closer to the earth than many other feathered migrants.
What sketchy information available suggests ruby-throated hummingbirds migrate close to the land. In fact, many appear to migrate very close to the tops of trees. It is believed that this enables the tiny migrants to spot places where they can refuel before resuming their journey.
This is not to say that some hummingbirds don’t fly much higher. Hot air balloonists have reported seeing rubythroats cruising along upwards of 500 feet above the ground.
Once rubythroats reach the Gulf of Mexico, they appear to wing their way along just above the tops of the waves. This conclusion is based on sightings made by men and women working on oil and gas platforms far from shore in the Gulf of Mexico and fishermen seeing these tiny, feathered dynamos zipping along close to the waters of the Gulf. These sightings appear to indicate ruby-throated hummingbirds migrate closer to the earth than many other migrants.
Most small birds migrate at altitudes ranging from 500 to 1,000 feet. Raptors migrate anywhere from 700-4000 feet up whereas waterfowl migrate to and from their breeding grounds at altitudes of 200-1450 feet high.
However, a mallard was once struck by an airplane flying 21,000 feet above the earth.