Via the American Bird Conservancy
Where the high flying bird vanishes to after breeding and spending summers in many parts of western North America has puzzled ornithologists since the species was discovered in 1857. Now, thanks to a new study, we learn that at least some of them travel about 4,300 miles to a remote part of western Brazil in lowland rainforest.
The study, which was published in the March 2012 issue of Wilson Journal of Ornithology, involved attaching geolocators (tiny devices that record and store tracking information) to four adult Black Swifts from two nesting sites in Colorado, then recapturing the same birds at the same sites the next year to download the stored data. Three of the four tracking devices were recovered, and showed the birds departing for their fall southerly migration between September 10 and September 19, arriving in Brazil between September 28 and October 12, departing Brazil between May 9 and 20, and arriving back at their Colorado breeding sites between May 23 and June 18.
Further, satellite GPS devices, which transmit real time tracking of individuals, are not sufficiently small to place on a species the size of the seven-inch-long Black Swift. As a result, geolocators (which record data but do not transmit it) were used which meant that the study birds would need to be recaptured for the location data to be analyzed. That necessity was made easier on one hand by the fact that the birds typically are very committed to returning to their previous breeding colony, but made more challenging because they tend to nest in areas that are incredibly difficult to access – behind waterfalls in deeply shaded niches in steep and narrow canyons.
Curiously, the birds averaged about 211 miles per day during fall migration and about 244 miles per day during spring migration, about a 15 percent increase in average daily distance covered. They spent about 220 days in Brazil before migrating north again.