Keeping Cool — Gauging the Effects of Climate Change on Honeycreepers

Editor’s Note: This is the fifth in a six-part series

AT HIGH altitude, relatively few malaria-bearing mosquitoes are able to survive in the cool air — but with predicted temperature changes, the insects can expand their range, adding new pressures to the island’s disease-susceptible bird populations. 

Native forest birds in the Hawaiian Islands have adapted to life at higher elevations over the past 30 years. With no natural protection against diseases such as avian malaria (Plasmodium spp.), susceptible birds are provided with ‘disease-free’ strongholds at higher elevations where the temperatures have historically been too low for the survival of the malaria parasite and the disease-carrying mosquitoes which like warm and wet conditions. Put in other words, how cold it is limits the distribution and population sizes of malaria-carrying mosquitoes, and thus of many Hawaiian birds.

In Hawaii, more than 20 forest bird species live on cool, high elevation mountains — above 4000 ft — such as Puu kukui (shown above) where mosquitoes don’t thrive. However, a warmer climate is enabling these diseases to spread, as malaria-bearing mosquitoes are no longer being killed by prolonged winter cold.

Given the threat of climate change, these mosquitoes will likely creep up the volcanoes, bringing their parasitic passengers along for the ride. So as malaria rises up slope, the amount of disease-free refuge will shrink. And of course, this would have a devastating effect on populations of honeycreeper, and other native forest birds as well.

“Without question, the one factor that prevented widespread and rapid extinction of virtually all of Hawaii’s native honeycreepers after the introduction of avian malaria was the presence of high-altitude disease refuges on Kauai, Maui and Hawaii,”

Dr. Carter Atkinson, a U.S. Geological Survey (USGS) microbiologist based at the USGS Pacific Islands Ecosystems Research Center in Hawaii.

High elevation areas have served as "refugia" on Kauai, Maui and Hawaii, sustaining forest bird populations.

High elevation areas have served as “refugia” on Kauai, Maui and Hawaii, sustaining forest bird populations. Ten years ago, you could practically count on one hand the number of native birds infected with malaria at 1900m on the island of Hawaii. Nowadays you couldn’t, unless you had more than double the amount of fingers.

And when it comes to funding and planning, there isn’t enough, both in Hawaii and the rest of the world, despite our general awareness of the potentially devastating effects of malaria on susceptible species. Atkinson says that when it comes to general funding for conservation of endangered forest birds, that it “needs to be increased by orders of magnitude if we are to avert a biological disaster in our lifetimes”.

Nobody denies that recent global efforts have made enormous progress in saving human lives, or that today’s avian extinction rate far exceeds that of just two decades ago.  Yet, the issues that face birds globally are largely being ignored, says George Fenwick, president of the American Bird Conservancy. And that’s not a good sign.  After all, most studies seem to show that malaria has been largely responsible for the recent wave of extinctions and endangerment among Hawaiian forest birds.

Many native Hawaiian birds that are considered “endangered” have already proven to be highly susceptible to disease in the wild. Nowadays, if you want to see a live honeycreeper you have to go to the tops of mountains, no less than 1500m (4920ft). There are exceptions – like the Hawaii Amakihi Hemignathus virens that still remains widely dispersed – but usually the birds only persist where temperatures prevent effective malaria development in mosquitoes. But at high altitudes, Atkinson maintains that it is quite likely that threatened bird species will be “squeezed between expanding disease transmission from lower elevations and the upper limits of suitable forest habitat“ due to a predicted rise in global temperature over the next  century.


Many native bird species on islands, such as Kauai, are highly impacted by avian malaria. Over time, avian malaria has forced most of these species to breed in high elevation refugia where food and cover may be scarce. Refugia or “safe havens” are areas where natural environmental conditions have remained relatively constant or stable during times of great environmental change.

Alas, as tempting as it maybe to write a comprehensive list on climate change and the altitudinal range of avian malaria in the Hawaiian Islands, this was not meant to be one. Plenty of those exist though. So for now, aside from what information is here, your best bet might be to check this 2014 publication out for more detailed information or look at this USGS update for some interesting facts and figures!

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Hawaiian honeycreepers are in Peril-Why the native forest birds may become extinct.

Editor’s Note: This is the fourth in a six-part series.

HAWAII-It is considered the “global epicenter of imminent extinctions”  for plants and animals; just since the 1980s, 10 unique birds have disappeared. Among some of the most threatened species are a native group of forest birds known as honeycreepers (Drepanidinae) that have evolved in the absence of avian malaria. 

As you can see (below), these beautiful and fascinating birds have evolved  a remarkable array of distinctive morphologies.


Family Drepanididae (Hawaiian Honeycreepers). *Note* Not all species are shown.

[VIDEO] Are you looking to see what a Purple,Green, Shining, Golden collared or Red-legged honeycreeper looks like?

Hawaii has more extinct birds than anywhere else in the world

Hawaii has more extinct birds than anywhere else in the world

Honeycreepers have suffered catastrophic decline in recent decades due to:

  • Habitat loss
  • Introduction of alien plants and animals
  • Avian disease

The accidental introduction of the southern house mosquito Culex quiquefasciatus– a non-native species –  into Hawaii  (1826) has allowed avian malaria and avian pox to spread, putting 33 species of the 42 remaining birds species in danger of extinction.

Clearly, the rapid loss of native island floras and faunas is a huge cause for concern among scientists.

We have five, 10, maybe 15 years before we start seeing more declines…but some of these species don’t have that much time and I don’t want to see another species become extinct in my lifetime. 

Pete Marra, director of the Smithsonian Institution’s Migratory Bird Center .

hawaii colonise

The introduction of avian malaria (Plasmodium relictum) to the remote Hawaiian Islands is believed to have played a major role in the decline and extinction of several native bird species. Now, less than half of Hawaii’s previously extant species of honeycreeper still exist.

Symptoms include:

*Anemia. The loss of red blood cells leads to a…

*Lack of oxygen and progressive weakness.

*And eventually deathbirds that have never had tolerance to malaria can get it very quickly and die from it. Mortality in many native species can range from 50 to 90%. In contrast, mortality in introduced bird species appears to be negligible.



Species-differences in susceptibility to disease.

Example:`I`iwi vs`Apapane

The ‘i’iwi (A) is very susceptible to malaria, whereas the ‘apapane (B) less so.

*NOTE*  The differences in disease susceptibility are for reasons yet to be determined

Nature conservancyToday, threatened by habitat destruction, introduced predators and avian diseases, the ‘i‘iwi is extinct on the island of Lāna‘i, and is considered extremely rare and vulnerable to extinction on O‘ahu and Moloka‘i.

Iiwi honeycreeper

A)’I’iwi honeycreeper.  The ‘I’iwi is easily Hawaiis most recognizable forest bird. As well as habitat loss, Hawaii’s massive bird losses are blamed on introduced mosquitoes, which carry diseases like avian malaria.

'Apapane honeycreeper

B) ‘Apapane honeycreeper

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