Bird­ing

Arc­tic birds’ breed­ing and win­ter­ing grounds are warm­ing, and that hurts them coming and go­ing

Canadian Wildlife - - CONTENTS - By David Bird

Tim­ing’s Off: Arc­tic birds’ breed­ing and win­ter­ing grounds are warm­ing, and that hurts them both coming and go­ing

When­ever I am asked to com­ment on the im­pact of cli­mate change on Arc­tic birds, two words im­me­di­ately pop into my mind: win­ners and losers. And the for­mer are in a very small mi­nor­ity among the 85 bird species that breed in the globe’s north­ern re­gions. Be­ing highly mo­bile crea­tures, birds will not be as hard hit as those or­gan­isms liv­ing year-round in the Arc­tic. But both breed­ing and win­ter­ing grounds will be af­fected.

One of the most crit­i­cal is­sues in­volves tim­ing. Ac­cord­ing to one large-scale study, birds are ini­ti­at­ing egg-lay­ing at an av­er­age rate of 6.6 days ear­lier every 10 years. The com­mon murre, a seabird breed­ing widely through­out the Arc­tic, is 24 days ear­lier per decade. This is a bad thing be­cause raising young is no longer matched with the time of best food avail­abil­ity. This has two neg­a­tive ef­fects: par­ent birds are un­able to feed their off­spring suf­fi­ciently; and later, fledglings will be un­able to find ad­e­quate food to fat­ten up be­fore mi­gra­tion.

Ris­ing tem­per­a­tures af­fect mi­gra­tion too: birds are mi­grat­ing ear­lier be­cause of warm­ing spring tem­per­a­tures. A 63-year study of 96 long-dis­tance mi­grant species con­cluded that more than a quarter of them are ar­riv­ing ear­lier. But many of these same species are not re­turn­ing north any ear­lier. Since they can­not know what weather and food con­di­tions are like on their breed­ing grounds in the Arc­tic, they may well ar­rive to dis­cover there’s barely enough to sur­vive on, let alone fat­ten up enough to pro­duce eggs. Spe­cial­ist species that eat only one or two foods will be es­pe­cially hard hit. For ex­am­ple, ivory gulls, which specif­i­cally for­age along dis­ap­pear­ing sea ice, have de­clined by 90 per cent in just the last 20 years.

With en­tire eco­log­i­cal com­mu­ni­ties be­ing dis­rupted by cli­mate change, Arc­tic birds are chal­lenged by a whole army of new par­a­sites, preda­tors and com­peti­tors to which they are not adapted. Thick-billed mur­res breed­ing in north­ern Hud­son Bay are ex­pe­ri­enc­ing higher egg loss and adult mor­tal­ity due to a com­bi­na­tion of heat and greater num­bers of mos­qui­toes. Habitat changes can also be in­di­rect, as warmer con­di­tions cou­pled with less snow and ice bring more tourism and re­source de­vel­op­ment with all their as­so­ci­ated in­fra­struc­ture to the Arc­tic.

Sci­en­tists from the Univer­sity of Queens­land in Aus­tralia cre­ated a re­search model that took cli­mate breed­ing con­di­tions for 24 Arc­tic bird species and pro­jected them into 2070. They gloomily pre­dicted that more than 80 per cent will lose vir­tu­ally all of their breed­ing habitat.

In a re­search re­port from the Wildlife Con­ser­va­tion So­ci­ety in the United States, nine species were iden­ti­fied as ei­ther highly or mod­er­ately vul­ner­a­ble due to changes spe­cific to Alaska (not tak­ing into ac­count changes else­where in their range). Of the two most vul­ner­a­ble one is the gyr­fal­con, for decades now my favourite bird. Other, long-term gyr­fal­con stud­ies in Greenland re­veal sig­nif­i­cant in­cur­sions of more ag­gres­sive pere­grine fal­cons into their hunt­ing grounds and their nests. Then again, the pere­grines are hav­ing their own cli­mate change prob­lems in Greenland: mas­sive in­creases in rain­fall (a whole sea­son’s worth fall­ing in a mere three hours) is caus­ing pere­grine nestlings to drown or die of hy­pother­mia. Fal­con ex­perts there feel it is just a mat­ter of time be­fore one of the two species will be­come ex­tinct.

These are just a few of the losers in the re­al­ity that is cli­mate change.

Ac­cord­ing to one large-scale study, birds are ini­ti­at­ing egg-lay­ing at an av­er­age rate of 6.6 days ear­lier every 10 years. This is a bad thing be­cause raising young is no longer matched with the time of best food avail­abil­ity

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