Do Hummingbirds Hum?: Fascinating Answers to Questions about Hummingbirds

FIVE: Flight and Migration

FIVE Flight and Migration Question 1: How far can a hummingbird fly? Answer: The distance hummingbirds fly varies from species to species, and even among populations of the same species in different locales (see this chapter, Question 5: Do all hummingbirds migrate?). Some hummingbirds fly very long distances when they migrate, but learning the details about migratory patterns is challenging, since birds must be banded or individually marked and recaptured later in sufficient numbers to yield useful information. Understanding migration is crucial in order to anticipate the consequences of future habitat loss and climate change on bird distribution. Bridget Stutchbury of York University in Toronto and her colleagues attached tiny tracking devices weighing just 0.05 ounces to migratory songbirds to record their movements. When some of the birds were recaptured, the data from their backpacks were downloaded and their daily movements could be mapped. This is a promising development that will be expanded to larger numbers of birds—and perhaps one day greater miniaturization will allow the project to extend to hummingbirds so we can measure exactly how far they fly. Most hummingbirds found north of Mexico and in southern Argentina and Chile are highly migratory, spending the summer and winter in completely different areas. A bird prepares to migrate by spending a few days to a few weeks feeding and converting sucrose into fat that is stored for the first leg of the 88 DO HUMMINGBIRDS HUM? journey (see this chapter, Question 2: How are hummingbirds able to fly so far?). As described by William Calder, formerly a University of Arizona ornithologist, the champion migrant is the Rufous Hummingbird. Some banded individuals have traveled a minimum of 2,700 miles one way, from the northern edge of their nesting range in Alaska to the northern edge of their wintering range in Mexico. This distance equals 49 million body lengths, one of the longest migrations in proportion to size of any creature. The trip is not accomplished all in one flight, but rather in a series of short flights from one flower patch or feeding area to the next. Robert Gill and colleagues from the Alaska Science Center used satellite telemetry and surgically implanted transmitters to track shorebirds, Bar-tailed Godwits Limosa lapponica baueri, that migrate nonstop across the central Pacific Ocean, a distance of almost 4,500 miles. Scientists have considered oceans, mountain ranges, ice fields, and deserts as barriers to the movement of land-dependent animals, but this research suggests that a transoceanic route may function as “an ecological corridor rather than a barrier, providing a wind-assisted passage relatively free of pathogens and predators.” The research has fascinating implications for understanding how Ruby-throated Hummingbirds manage their migration across the Gulf of Mexico, a distance of about five hundred miles, and the longest nonstop migration route of any species of hummingbird. In proportion to the relative distances and sizes of the birds, it surpasses the achievement of the Bar-tailed Godwits, approximately one hundred times larger, crossing the Pacific Ocean. If hummingbirds fly over the water at their normal speed of about twenty-five miles per hour, it would take them twenty hours to make the trip. We assume that this flight starts when the weather is good, often in late afternoon, and continues overnight so that birds reach land in early morning daylight. We expect that birds once underway fly with the most advantageous winds that will carry them in the right direction, increasing their speed and shortening the time needed to cross the water. Birds can move up and down to fly at different altitudes, taking Figure 23. Top, migration routes of Rufous Hummingbirds Selasphorus rufus , from their northern breeding range that extends to just south of Anchorage , Alaska, to Mexico and the Gulf Coast of the United States. Researchers believe that most of the population travels a circular route, flying north along the Pacific Coast from Mexico through California to their breeding grounds in the north, and returning south along the Rocky Mountain chain; bottom, migration routes of Ruby-throated Hummingbirds Archilochus colubris to their wintering range in Mexico and Central America. Some individuals winter in the southern tip of Florida. 90 DO HUMMINGBIRDS HUM? advantage of favorable winds to help their migration travel. Tara Rodden Robinson, an ornithologist from the University of Illinois, reported that not all Ruby-throats cross the water, and many move south along the Texas...