| Abstrakt: |
Host to a concentration of roughly 250,000 birds between February and April, it's one of the largest Purple Martin roosts ever discovered. JUST OFF A SPLINTER OF LAND SITTING MID-stream in Brazil's RioNegro, a crew of scientists in two boats intently scan the sky. Seven years later Stutchbury's postdoc Kevin Fraser, now an ornithologist at the University of Manitoba, equipped 105 Purple Martins with more advanced trackers: GPS devices that could place a bird to within about 30 feet. Natural cavities, such as tree hollows, once ofered ample nesting sites for Purple Martin colonies, but the loss of those - coupled with competition from aggressive, non-native species like the European Starling - has made the birds "100 percent reliant on humans providing housing for them to reproduce", Siegrist says. [Extracted from the article] |
