I had the pleasure last weekend to be a part of the 27th annual Hummer/Bird Celebration in the Rockport and Fulton Beach area of the middle Texas Gulf Coast Region. The focus of the celebration/nature festival is the gathering of large numbers of Ruby-throated Hummingbirds prior to their return to the tropics where the majority of them spend the winter. In March and April the middle and upper Texas Gulf Coast are the sites of these same hummingbirds’ arrival from the tropics after a thirty-plus-hour non-stop flight from the Yucatan Peninsula covering a distance of over five hundred miles.
There is consensus of opinion that these hummingbirds make this arduous flight every spring from the tropics in route to their breeding grounds all across the eastern half of the United States and southern Canada. The males are eager to get to their breeding grounds to claim the most attractive habitat to increase their chances for a successful attempt to promote their species’ survival. After the breeding season is concluded the urgency to claim a territory in the tropics is not as important an issue as when they arrived from the tropics, so they tend to take more time and wander around as they head south.
If time is not an issue, an obvious question becomes whether the hummingbirds would take the more stressful trip by flying south across the Gulf of Mexico, or take the longer, but safer route over land through eastern Mexico. A difference of opinion exists amongst ornithologists regarding which route these tiny travelers take on their return to the tropics. I have always assumed that they returned over the same route used in their northern travel. In discussion with several of my colleagues who gave talks this past weekend, I found that several of them favor the over land hypothesis rather than the over water scenario.
My colleagues seem to base their belief on the limited documented evidence of birds arriving in the Yucatan Peninsula region where the birds launched their northward trip in the spring. The limited reports of exhausted birds landing in the peninsula region do not match the many known observations of exhausted birds arriving on the Texas coast in the spring. The reason for this difference according to the argument is that the birds take the safer, less stressful route over land in Mexico in the fall migration. I have no hard evidence based on my experience to refute these claims, but I believe the rubythroats take the reverse route they took in the spring. I believe my theory makes more logical sense.
My opening point to my case relates to the fact that the hummingbirds stage in the central Texas coastal bend region to bulk up on sugar water and flower nectar to have the necessary fat to provide the energy to make the over-water flight. I have stood on the shoreline south of Rockport and seen many hummingbirds whiz by heading directly offshore, rising in altitude as they get out over the water. However, that they start out over water is not proof that they stay over water the entire distance to first landfall on the Yucatan Peninsula.
My thinking is that the hummingbirds take advantage of the Northern Hemisphere trade winds that blow from northeast to southwest in the summer and fall months. These prevailing winds give the travelers a slight tail-wind advantage to help them conserve energy and to nudge them westward. These winds could cause them to make landfall south of the coastal city of Veracruz and west and northwest of Yucatan. The region south of Corpus Christi all the way to Veracruz is more of a desert with limited food sources; therefore, the land route would be as difficult as the route over water.
We will not likely solve this mystery route until GPS tracking devices are reduced in size to allow the hummingbirds to carry them without endangering their safety. This technology development may take several more years to produce, and until then, we will continue to have differences in opinions as to whether they travel over sea or land. Maybe the answer will be that the birds do both.