Among the many breakthroughs provided by the migration-tracking devices known as light-level geolocators, one of the most surprising is how many birds use multiple winter sites, not one.
The list includes Veery, Swainson’s Thrush, Red-backed Shrike, and Fork-tailed Flycatcher. According to research published in a recent issue of The Auk, the journal of the American Ornithologists’ Union, Eastern Kingbird and Western Kingbird belong on the list as well.
Variations in rainfall and food availability probably underlie the winter movements, says investigator Alex E. Jahn of the University of Florida. He and colleagues color-banded and outfitted flycatchers with geolocators in Nebraska and Oklahoma in the summers of 2010 and 2011.
Departing in August or early September, Eastern Kingbirds flew 4,000 miles to Bolivia and Brazil in the southern Amazon Basin. Then, after an average of 100 days, they moved to a second wintering area in northwestern South America (in the countries of Colombia, Ecuador, and northern Peru), where they remained 75 days.
Western Kingbirds left their breeding grounds earlier, toward the end of July, and didn’t fly as far. They moved about 900 miles to Baja California, Baja California Sur, and Sonora in northwestern Mexico. Then, in November or December, they moved to another wintering area stretching from southern Mexico to northern Central America, where they remained until April.
Jahn and his team also tracked Scissor-tailed Flycatchers. They made their migration in mid-October, later than the other birds, and used only one winter site, in El Salvador, Guatemala, Honduras, and Nicaragua.
In the spring, most Eastern Kingbirds crossed the Gulf of Mexico, departing from or near the Yucatán Peninsula. One took 42 days to complete the return trip, but all other birds returned in less than four weeks, and most arrived on the breeding grounds before mid-May.
Scissor-tailed Flycatchers and Western Kingbirds took as little as 16 days to migrate north, arriving by mid-April and early May, respectively.
Read the abstract
Jahn, Alex E.; Cueto, Víctor R.; Fox, James W.; Husak, Michael S.; Kim, Daniel H.; Landoll, Diane V.; Ledezma, Jesús Pinto; LePage, Heather K.; Levey, Douglas J.; Murphy, Michael T.; Renfrew, Rosalind B., 2013, Migration Timing and Wintering Areas of Three Species of Flycatchers (Tyrannus) Breeding in the Great Plains of North America, The Auk 130 (2): 247-257, doi: 10.1525/auk.2013.13010. Abstract.
A version of this article appeared in the October 2013 issue of BirdWatching magazine.
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