The world’s long­est run­ning study of a sta­ble rap­tor pop­u­la­tion just cel­e­brated its 50th sea­son. Be­hind the re­search on these thriv­ing ea­gles of bo­real Saskatchewan.

Canadian Geographic - - SHARING CAN GEO VIA INSTAGRAM -

Wreaches the rim of the bald ea­gle nest, the spruce nee­dle-blan­keted for­est floor lies more than 20 me­tres be­low. For many, a healthy fear of heights might have kicked in around me­tre 10 of the climb, but white spruces are thick with branches and, says Ger­rard, more or less like lad­ders. But it also helps that he’s done this re­peat­edly ev­ery July for 50 years. At 69, the long­time pe­di­a­tri­cian, or­nithol­o­gist, politi­cian and, as of June 2017, con­tes­tant for leader of the Lib­eral Party of Man­i­toba, is still quick to scram­ble up the bo­real gi­ants that ring Besnard Lake, pro­vided they’re home to one of the many bald ea­gle nests he and his team have lo­cated and col­lected data on since 1968. Star­ing back across this 1½-me­trewide nest are two strap­ping ea­glets, both hop­ping and grunt­ing au­da­ciously. No white-capped adults are in sight. At this time of year, the young are typ­i­cally 50 to 60 days old — fully feath­ered and al­most three-quar­ters of their even­tual three- to six-kilo­gram weight, but a few weeks from fledg­ing. Ger­rard coaxes them for­ward, one by one, by nudg­ing them from be­hind with a stick from the nest, grasps their legs above the talons and zips the birds into duf­fle bags, which he then low­ers to the ground on climb­ing ropes. Within a few min­utes, El­ston Dzus, an Al­ber­taPa­cific For­est In­dus­tries ecol­o­gist who started com­ing to the lake in 1984 as a Univer­sity of Saskatchewan un­der­grad, or other re­searchers and fam­ily mem­bers at ground level have banded, mea­sured and de­ter­mined the sex of the birds and sent them back up. Re­turned to their aerie, the sib­lings are an­noyed but not ag­i­tated, and Ger­rard bids them good­bye as he starts his des­cent. By the end of the field sea­son, the group has tal­lied seven new nests, bring­ing the to­tal to about 50 on the lake. With 32 young born in 25 of those nests, 2017 marks the high­est num­ber of suc­cess­ful

nests in the study’s 50 years, says Dzus, and among the top counts in terms of chick pro­duc­tion. It’s been an­other good year for the world’s long­est-run­ning study of a sta­ble rap­tor pop­u­la­tion.

IF YOU THINK A LAKE in bo­real Saskatchewan, 370 kilo­me­tres north of Saska­toon, seems like an un­likely place for a thriv­ing pop­u­la­tion of bald ea­gles, you’d be in good com­pany. Even as the Besnard Lake study was tak­ing shape in the late 1960s, the stan­dard or­nitho­log­i­cal ref­er­ence Birds of Canada de­scribed bald ea­gles as com­mon on the At­lantic and Pa­cific coasts but lit­tle more than a rare and pic­turesque species in be­tween. But in 1966, when Ger­rard and his friend Doug Whit­field were ca­noe­ing the Saskatchewan side of the Churchill River, they “re­al­ized there were ea­gles up there.” Given that the pair had met while band­ing owls, it was only nat­u­ral for them to plan a re­turn to the area for four straight week­ends the next year to find and band at least a cou­ple of ea­gle nestlings. When they did, they man­aged to pig­gy­back on he­li­copter and float plane rides with bi­ol­o­gists and pro­vin­cial wildlife con­ser­va­tion of­fi­cers who were work­ing in the re­gion, and made wide, al­beit cur­sory, sur­veys of parts of the Cum­ber­land Marshes and more northerly lakes around the Man­i­toba bound­ary. “On those week­ends we found 18 nests with 27 young, and we climbed up to and banded ev­ery one of them,” says Ger­rard. “We were ex­cited, starry-eyed. Af­ter that, the Cana­dian Wildlife Ser­vice gave us a grant to do aerial sur­veys, so in 1968 and ’69 we did a lot of fly­ing in north­ern Saskatchewan and a bit of Man­i­toba.” At the end of those sum­mers they had found al­most 250 ac­tive and in­ac­tive ea­gle nests — in­clud­ing those at Besnard Lake. The news of flour­ish­ing ea­gle pop­u­la­tions in cen­tral Canada’s re­mote bo­real for­est as­ton­ished the North Amer­i­can or­nitho­log­i­cal com­mu­nity, who had been watch­ing birds of prey van­ish at an alarm­ing rate, es­pe­cially from the east­ern United States, due to the pes­ti­cide DDT (banned in Canada in 1970). An ex­ten­sive aerial sur­vey of north­ern Saskatchewan i n 1974 re­vealed more than 14,000 bald ea­gles in some 3,900 breed­ing ar­eas. from south­west to north­east tip and — most im­por­tantly for ea­gles seek­ing sturdy, tall wa­ter­front spruce, trem­bling as­pen and pine for their im­mense nests — with more than 400 kilo­me­tres of shore in­clud­ing 250 is­lands, Besnard Lake was nearly sat­u­rated with ea­gle ter­ri­to­ries when Ger­rard ar­rived. “We had a whole lot of ques­tions about these bo­real breed­ing grounds,” he says. “And Besnard was a per­fect study area for many rea­sons. There were lots of ea­gles, but it was also a large lake with­out a town or city on it.” It’s also teem­ing with white sucker and cisco, the most com­mon fish to spot thrash­ing in an ea­gle’s grasp, though they’ll also carry pike, wall­eye and even deep-dwelling bur­bot to their nests. What makes this l ake pro­duce enough fish to sus­tain around 100 ea­gles, two fish­ing lodges and the own­ers of 70-odd cab­ins is its ge­og­ra­phy.



A ju­ve­nile bald ea­gle re­acts to be­ing banded (op­po­site top). El­ston Dzus (op­po­site bot­tom, left) re­views fresh drone footage on Besnard Lake. An adult pair of bald ea­gles calls from a wa­ter­side perch (pre­vi­ous page). FORTY-THREE KILO­ME­TRES

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