Study re­veals cli­mate changes are af­fect­ing na­tive birds

Hawaii Tribune Herald - - FRONT PAGE - By JEFF HANSEL

Re­searchers say cli­mate changes are af­fect­ing the in­dige­nous birds of Hawaii.

“The con­ser­va­tion chal­lenges that the state is fac­ing are so se­vere,” said U.S. For­est Ser­vice Ecol­o­gist Jared Wolfe.

The na­tive Hawai­ian birds that were stud­ied time their mat­ing to match abun­dance of lehua blos­soms on ohia trees — the more flow­ers, the grander the bird pop­u­la­tions.

Ohia trees are among the first to col­o­nize new lava de­posits. But ohia forests are at risk from the fun­gal dis­ease known as rapid ohia death. And when ohia trees are af­fected by drought, the num­ber of nec­tar-lov­ing birds, such as ‘i‘iwi and ‘apa­pane, dwin­dles.

Nec­tar-lov­ing Hawai‘i ‘amak­ihi, which also eat other foods, re­main un­af­fected.

When rains re­turn, and lehua flow­ers flour­ish, the pop­u­la­tions of ‘i‘iwi and ‘apa­pane re­bound.

An ar­ti­cle ti­tled “Bot­tom-up

Pro­cesses In­flu­ence the De­mog­ra­phy and Life-cy­cle Phenol­ogy of Hawai­ian Bird Com­mu­ni­ties” was pub­lished in Septem­ber by the jour­nal Ecol­ogy, a peer-re­viewed re­search pub­li­ca­tion of the Ecol­ogy So­ci­ety of Amer­ica.

Wolfe, lead au­thor of the study, said dur­ing a tele­phone in­ter­view that the re­search is im­por­tant be­cause ohia trees are a “crit­i­cal com­po­nent of the Hawai­ian ecosys­tem.” He also noted in a state­ment an­nounc­ing the study that “our re­sults sug­gest that changes in cli­mate can cas­cade up the food chain and strongly af­fect wildlife at higher lev­els in the chain.”

Wolfe and col­leagues at the U.S. For­est Ser­vice Pa­cific South­west Re­search Sta­tion “re­viewed ex­ten­sive cli­mate, veg­e­ta­tion and bird data col­lected be­tween 1976 and 1982 at a 40-acre mon­i­tor­ing site about 5 miles out­side Hawaii Vol­ca­noes Na­tional Park on Hawaii Is­land,” says a news re­lease an­nounc­ing the study.

“The data was ac­tu­ally col­lected when I was a kid,” Wolfe said.

Ex­traor­di­nar­ily de­tailed data was col­lected about plants and birds, in­clud­ing weather, tim­ing of flow­er­ing, fruit­ing, mat­ing and molt­ing — a vul­ner­a­ble pe­riod when birds lose feathers.

“These types of data sets are very rare,” Wolfe said. When he learned about the data’s ex­is­tence, he sought the op­por­tu­nity to use it to bet­ter un­der­stand cli­mate change.

A key find­ing of the study is that “changes in cli­mate can in­flu­ence the food that’s im­por­tant to birds,” Wolfe said.

The study on Hawaii Is­land was im­por­tant to the study of cli­mate change over­all be­cause the is­land is a rel­a­tively iso­lated en­vi­ron­ment, which means re­searchers could dis­count other po­ten­tial causes of their con­clu­sions.

Such other causes, known to sci­en­tists as “con­founders,” can skew re­search re­sults. In this study, con­founders could have in­cluded main­land char­ac­ter­is­tics such as ir­ri­ga­tion, pes­ti­cide ap­pli­ca­tion or co­pi­ous back­yard bird feed­ers. None of that was present at the study site.

Birds that are ob­li­gate nec­tar feed­ers such as ‘i‘iwi and ‘apa­pane, mean­ing they must con­sume nec­tar, Wolfe said, “are sub­ject to sud­den pop­u­la­tion de­cline” di­rectly stem­ming from food sup­ply.

The birds stud­ied weren’t able to switch tem­po­rar­ily to an­other food source un­til lehua blos­soms were re­plen­ished.

“We found that Hawai‘i ‘amak­ihi, a di­etary gen­er­al­ist, was the only na­tive nec­tar-feed­ing study species … to have a sta­ble pop­u­la­tion,” the jour­nal ar­ti­cle says.

Such birds were able to feed on other food sources in­clud­ing bugs or berries in the in­terim when nec­tar wasn’t avail­able.

The study will be im­por­tant when look­ing at cli­mate change in the years to come, Wolfe said.

He noted the study was ob­ser­va­tional. So it pro­vides a historical bench­mark from the late ‘70s and early ’80s as a start­ing point. But, he noted, now the “cli­mate’s chang­ing so quickly” that it’s hard to study.

Wolfe asks the pub­lic to “sup­port good sci­ence, sup­port good sci­en­tists who can work ‘out­side the box.’”

The jour­nal ar­ti­cle states “the fu­ture of na­tive Hawai­ian birds may de­pend on their be­hav­ioral plas­tic­ity to mit­i­gate changes in food re­sources and to suc­cess­fully com­pete with co-oc­cur­ring non­na­tive bird species.”

“It’s sad that evo­lu­tion­ar­ily dis­tinct species are go­ing to be the most chal­lenged,” Wolfe said.

Courtesy photo

Life cy­cle changes and over­all species abun­dance were found to shift in na­tive Hawai­ian birds, such as the ‘i’iwi, to co­in­cide with cli­mate-re­lated changes to na­tive veg­e­ta­tion.

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