Where have all the song­birds gone?

Cli­mate change could be just an­other chal­lenge for N.L.’s gray-cheeked thrush, other dis­tinct species

The Compass - - Editorial - BY ASH­LEY FITZ­PATRICK afitz­patrick@thetele­gram.com

Once as com­mon as the robin, the gray-cheeked thrush has been listed un­der this prov­ince’s En­dan­gered Species Act since 2015.

Sci­en­tists are still work­ing to fully un­der­stand what hap­pened to the song­birds, and what their fu­ture might hold.

The fu­ture also means think­ing about the un­cer­tain­ties as­so­ci­ated with global cli­mate change.

The gray-cheeked thrush was one of the most com­monly spot­ted birds dur­ing sur­veys in New­found­land and Labrador in the 1970s.

Parks Canada ecosys­tem sci­en­tist and or­nithol­o­gist Dar­roch Whi­taker told the Tele­gram the lo­cal pop­u­la­tion then dropped by more than 95 per cent at lower el­e­va­tions, all but dis­ap­pear­ing.

He said it was only dur­ing the ini­tial in­ves­ti­ga­tion that some of the birds were dis­cov­ered again in patches — mainly at higher el­e­va­tions — in Gros Morne Na­tional Park and in the Long Range Moun­tains.

The­o­ries then emerged around both the rapid change in the num­bers and dis­tri­bu­tion in­clud­ing: loss of habi­tat, pre­da­tion on bird nests and in­creased deaths dur­ing mi­gra­tion and win­ters down South.

Whi­taker said he com­mit­ted to fur­ther re­search be­cause the birds are part of the prov­ince’s unique nat­u­ral her­itage and have sig­nif­i­cance in terms of its bio­di­ver­sity.

In fact, while gray-cheeked thrush are found in sum­mer through­out the world’s bo­real for­est, the lo­cal pop­u­la­tion has re­turned to New­found­land an­nu­ally, with some in south­ern Labrador.

And for thou­sands of years and gen­er­a­tions, with the re­turn­ing birds not breed­ing with larger main­land pop­u­la­tions and adapt­ing to the par­tic­u­lar en­vi­ron­ment, a ge­net­i­cally dis­tinct, lo­cal pop­u­la­tion de­vel­oped.

There has been a sim­i­lar dis­cov­ery of dis­tinct ge­net­ics for more than 20 other bird species as­so­ci­ated with the prov­ince.

“From a con­ser­va­tion point of view, we really do fo­cus on those unique ge­netic units or pop­u­la­tion units within species and we do try and pre­serve those to main­tain the over­all bio­di­ver­sity of species,” Whi­taker said.

He teamed with Ian Warkentin, a pro­fes­sor in en­vi­ron­men­tal sci­ence at Gren­fell Cam­pus, Memo­rial Univer­sity of New­found­land (MUN), who also co-au­thored the “Birds of New­found­land” field guide.

Their sub­se­quent work con­firmed the change in dis­tri­bu­tion and also used DNA test­ing to firm up the gray-cheeked thrush tax­on­omy. Through part­ners in the United States, blood and tis­sue sam­ples from birds in New­found­land, Labrador and Nova Sco­tia have wound up archived at New York State Mu­seum.

En­ter: the squir­rel

The re­searchers also, “found that thrushes were greater than three times more likely to be de­tected at sites where squir­rels were not ob­served,” ac­cord­ing to a pa­per pub­lished in Avian Con­ser­va­tion and Ecol­ogy.

Red squir­rels were in­tro­duced to the is­land of New­found­land in the early 1960s and have spread out since, prey­ing on song­bird eggs and young.

And the gray-cheeked thrush is be­lieved to have started de­clin­ing in the 1970s.

Su­per­vised by Warkentin, masters of sci­ence stu­dent Jenna McDer­mott has been pro­vid­ing more de­tail on where squir­rels ac­tu­ally are now found in the prov­ince and ex­am­ined any re­la­tion­ship be­tween the thrushes and the squir­rel.

“So I’m work­ing in a sort of moun­tain­ous re­gion that ranges in elevation from 75 me­tres to 600 me­tres, and the red squir­rels only go up the moun­tains up to about 450 me­tres for the most part. Gray-cheeked thrush only start ap­pear­ing above 350 me­tres,” she said, in an in­ter­view Nov. 3.

“There’s only a very small over­lap be­tween where the two dis­tri­bu­tions are, and that sort of points to­wards red squir­rels be­ing a cul­prit here,” she said, adding she is still work­ing through two years of data and ob­ser­va­tions, col­lected from over 2,000 in­di­vid­ual points along the se­lected land­scape.

Migratory bird, global con­cern

But the po­ten­tial for the birds be­ing af­fected by en­vi­ron­men­tal change else­where is also be­ing in­ves­ti­gated.

McDer­mott has also spent time cap­tur­ing gray-cheeked thrush out­fit­ted with ra­dio tags over the past cou­ple of years, in or­der to gather data on where else the lo­cal birds might be stop­ping dur­ing their mi­gra­tions and call­ing home in win­ter.

The lim­ited data so far sug­gests they are re­main­ing in a fairly com­pact area in win­ter, mainly in Columbia.

Warkentin ex­plained this migratory con­nec­tiv­ity.

“Our pop­u­la­tion from New­found­land could well be go­ing to a very small, con­fined area of maybe Columbia, Venezuela, as op­posed to be­ing scat­tered all the way across what we know of as the gray-cheeked thrush win­ter­ing range,” he said.

Warkentin — still in­ves­ti­gat­ing other po­ten­tial in­flu­ences on the lo­cal gray-cheeked thrush pop­u­la­tion — said, at this point, he’s not con­vinced win­ter threats are part of the an­swer to what caused the pop­u­la­tion re­treat here, but this track­ing work and in­ves­ti­ga­tion is really a part of un­der­stand­ing the migratory species.

In terms of cli­mate change, it is a con­cern for migratory birds in gen­eral.

The New York Times re­ported in Jan­uary, re­searchers have found birds mov­ing be­tween Eu­rope and Africa, time their mi­gra­tions to match up with avail­abil­ity of food, but also mi­grate in loops rather than di­rect lines, ad­just­ing route and speed, fac­tor­ing wind and weather. Over time, those wind con­di­tions are ex­pected to change.

In May, a Duke Univer­sity-led study looked at how the tim­ing and tra­jec­tory of the sooty tern mi­gra­tion placed it in the path of At­lantic hur­ri­canes.

In­creas­ing hur­ri­cane in­ten­sity with cli­mate change be­comes a risk to the birds as a re­sult.

Whi­taker said the po­ten­tial for change in the habi­tat of the gray-cheeked thrush in New­found­land and Labrador is a con­sid­er­a­tion.

The higher el­e­va­tions where the birds are now found could be­come more hos­pitable to preda­tory squir­rels over time, adding pres­sure on the thrushes.

How­ever, this change is a slow process and the case is con­sid­ered one where a bet­ter un­der­stand­ing of the re­cent past and cur­rent threats re­main a pri­mary con­cern.


If you look closely, you can see a track­ing tag antenna ex­tend­ing from this bird’s back. To­day’s global po­si­tion­ing sys­tem and tag tech­nol­ogy al­lows the bird to be sent off with a tag weigh­ing about 1.5 grams, also able to record where it spends its win­ter.


Memo­rial Univer­sity of New­found­land grad­u­ate stu­dent Jenna McDer­mott is trained in the han­dling of song­birds for re­search pur­poses and, here, re­moves a tagged thrush from a mist net, to al­low for data to be down­loaded from its tag. The birds are then re­leased.


A red squir­rel.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.