New bird-track­ing tech­nolo­gies are lead­ing to star­tling dis­cov­er­ies and help­ing revise mi­gra­tion path­ways

Canadian Geographic - - CONTENTS - BY BRIAN BANKS

Ex­plor­ing car­tog­ra­phy

IIt’s been a mys­tery since the study of bird mi­gra­tions be­gan: while sci­en­tists un­der­stand a great deal about where birds breed, they know less about where they spend other times and, some­times, noth­ing about their travel routes. Over the last decade, though, re­searchers have started un­lock­ing many of th­ese un­knowns us­ing an ar­ray of evolv­ing track­ing tech­nolo­gies. The re­sult: a stream of rev­e­la­tions about mi­gra­tory birds’ jour­neys, their ca­pa­bil­i­ties and crit­i­cal des­ti­na­tions and haz­ards en route — es­sen­tial in­for­ma­tion for con­ser­va­tion work. “There are some sur­pris­ing find­ings,” says Dar­roch Whi­taker, an ecosys­tem sci­en­tist with Parks Canada, in Rocky Har­bour, N.L. “A lot of th­ese birds are mak­ing as­ton­ish­ing non-stop move­ments.” Take Con­necti­cut and black­poll war­blers, com­bined as one of six ex­am­ples of such dis­cov­er­ies de­picted on this map. Th­ese small song­birds, which weigh about as much as a triple-a bat­tery, spend sum­mer in Canada’s bo­real for­est and win­ter in South Amer­ica. But in 2014 and 2016, re­searchers found that in­stead of fly­ing south over land in the fall, they un­der­take a non-stop transat­lantic marathon — up­ward of 2,500 kilo­me­tres — from the East Coast of the United States to var­i­ous Caribbean is­lands be­fore reach­ing their fi­nal des­ti­na­tion. Th­ese con­clu­sions emerge from light-sens­ing ge­olo­ca­tors at­tached to the birds, one of the few de­vices small enough to be car­ried by birds this size. There are sim­i­lar light­weight tags that record a bird’s GPS co­or­di­nates at pre-set in­ter­vals. Birds must be re­cap­tured to col­lect this data. Other sen­sors, how­ever, sup­ply data that can be down­loaded re­motely, some­times in real time. For ex­am­ple, slightly larger GPS tags can send lo­ca­tion in­for­ma­tion when they’re in range of a re­ceiver. Oth­ers link di­rectly to satel­lites. Sci­en­tists us­ing a third op­tion, the Cana­dian-cre­ated Mo­tus track­ing sys­tem, fit birds with tiny nan­o­tag trans­mit­ters that emit a ra­dio sig­nal de­tected by more than 350 ground-based track­ing sta­tions through­out North and South Amer­ica when­ever a tagged bird passes nearby. As the ac­com­pa­ny­ing ex­am­ples show, all of th­ese meth­ods — cou­pled with break­throughs in DNA and iso­tope anal­y­sis that fur­ther pin­point in­di­vid­ual bird ori­gins — are yield­ing re­mark­able re­sults. “Mi­gra­tory birds have al­ways faced dan­ger­ous and daunt­ing jour­neys, but hu­man im­pacts have made such marathon flights all the more amaz­ing,” says Brid­get Stutch­bury, a bi­ol­ogy pro­fes­sor and Canada re­search chair in ecol­ogy and con­ser­va­tion bi­ol­ogy at Toronto’s York Univer­sity. “New tech­nolo­gies are im­por­tant for advancing ba­sic mi­gra­tion science, but also give us hope that pop­u­la­tion de­clines may some­day be re­versed.”

Whim­brel Whim­brels were among the first birds to show the power of mi­gra­tory track­ing tech­nol­ogy. In 2008 and again in 2012, whim­brels fit­ted with satel­lite trans­mit­ter tags were tracked con­tin­u­ously be­tween sum­mer breed­ing grounds in Alaska and the North­west Ter­ri­to­ries and win­ter­ing sites in Brazil. Of­ten, the birds spent days aloft. Wil­son’s war­bler There are five known breed­ing re­gions for this species in Canada, and birds born in each carry dis­tinc­tive ge­netic mark­ers. In 2014, sci­en­tists used DNA to match birds in var­i­ous win­ter­ing ar­eas in Mex­ico to their ar­eas of ori­gin. In 2015 and 2016, dozens of th­ese bo­real breed­ers were tagged with tiny ra­dio trans­mit­ters at over­win­ter­ing grounds in Colom­bia. Re­searchers then logged seg­ments of their spring­time moves north with the Mo­tus track­ing sys­tem, re­veal­ing links be­tween mi­gra­tion speeds — the fastest bird went 3,200 kilo­me­tres in a lit­tle more than three days, while some took weeks — and fuel avail­abil­ity at stopover sites.

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