During March 2015, a group of Swainson’s Thrushes were fitted with tiny radio-transmitters in Cundinamarca in the Eastern Andes of Colombia as part of a joint project between the University of Saskatchewan, SELVA and Environment Canada. The main objective was to determine how these migratory birds use pre-montane forest and shade coffee, and whether this affected how long they stayed in Colombia before commencing the long journey north to their breeding grounds in North America. The first surprise revealed by these tags was that birds stayed at their wintering site until mid to late April, which was much longer than expected. However, far more sensational news was to come. In late-May, we received the news that one of these individuals was detected by an automated receiving tower run as part of the Motus Wildlife Tracking System in Canada. The tower in question was one of just a handful in Saskatchewan run by the University of Saskatchewan. This may not seem that remarkable until one considers that Ana María González, whose team in Colombia fitted the bird with the transmitter, is a PhD student at the very same university. It seems that this bird was chasing Ana María back to Saskatchewan having left Colombia after the winter field season!
Two more birds from Cundinamarca were detected in North America, one in mid-migration on the Gulf coast of Texas and a second close to the end of its journey in southern Ontario. While these birds were initiating their journeys from Colombia in mid-April, a second group of birds was being tagged in the Sierra Nevada de Santa Marta in northern Colombia as part of the SELVA project, Crossing the Caribbean. This time the species was the Gray-cheeked Thrush and Camila Gómez, a PhD student at the Universidad de Los Andes, was using the tags to gain detailed information about habitat use and length of stay at a major refueling site, where this species stores enough energy to subsequently cross the Caribbean Sea and Gulf of Mexico to North America.
Two of the Gray-cheeked Thrushes tagged in northern Colombia were later detected in Canada. The first had made a remarkable journey of 3674 km in just 13 days, averaging 280 km per day. This ties in with SELVA’s research on the species, which suggests that they may fly between 2500 km and 3000 km from Colombia before they need to stop to refuel. This individual may well have crossed the Caribbean Sea and the Gulf of Mexico during a series of flights lasting three to five days, before stopping somewhere in the United States to refuel. When the bird was detected in Ontario, it was likely initiating the final leg of its journey to its boreal breeding grounds. The second bird was, incredibly, picked up by the only tower on the immense western shore of Hudson Bay. This location is close to the limit of the boreal forest with the tundra (5300 km from Colombia) and right in the heart of the remote breeding grounds of the Gray-cheeked Thrush. We believe that this represents the first direct evidence of the connection between the boreal breeding grounds of this species and a site in South America.
These fascinating insights into the routes, timing and speed of migration of inter-continental migratory thrushes were only made possible through multiple collaborations and SELVA would like to thank all those involved in making this possible: Stu Mackenzie (Bird Studies Canada), Keith Hobson (Environment Canada), Dr. Phil Taylor (Bird Studies Canada Chair of Ornithology at Acadia University), Motus Wildlife Tracking System, Universidad de los Andes, Colciencias, University of Saskatchewan, Coastal Bend Bays and Estuaries Program, Swarovski Optik, BirdLife International, Natural Sciences and Engineering Research Council of Canada, Western University, University of Guelph, and the Canada Foundation for Innovation.
We also want to thank the owners of Hacienda La Fragua, Cundinamarca, and Hacienda La Victoria in the Sierra Nevada for opening the doors to their farms and for their stewardship that makes their farms such excellent refuges for migratory birds.