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.

kaui-flights_1

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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What Causes Avian Malaria?

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

Beautiful and wonderful birds around the world are facing extinction due to avian diseases such as avian malaria. 

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Passerine birds-or perching birds- are the most common victims of avian malaria. But most penguins (non-passerine birds)  are very susceptible to Plasmodium and avian malaria is potentially disastrous for both wild and captive populations.

WHAT CAUSES AVIAN MALARIA

Plasmodium relictum, a protozoan parasite, is the main parasite that causes avian malaria and may be lethal to species which have not evolved resistance to the disease-infecting their red blood cells-or erythrocytes.

Wait, Mark! What are protozoan parasites?

This may sound complicated. But don’t fear! It’s pretty simple.

Most protozoa living in the environment are not harmful-they are what we call a eukaryotic organism but consist of only a single cell and so we need a microscope to be able to see them!

stock-footage-researchers-working-in-lab-with-microscope-close-up

Here’s a shiny looking microscope for ya!

Protozoan parasites, however, cannot live in the open environment on their own like other protozoa.

They’re different…

In fact, they mooch off other organisms (such as birds) to obtain protection and nourishment-cheeky indeed. However, scientists aren’t even sure of the number of protozoan species that induce avian malaria.

Oh, and by the way, the parasite is moved around by infected female mosquitoes-mostly Culex-where the mosquito picks up the parasite when it feeds on the blood of a infected bird, and then it passes the parasite on when it feeds again (on the blood of a non-infected bird).

Consider the Hawaiian Islands-Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, Maui and the Big Island. In this region, the mosquito that transmits the parasite is the common house mosquito, Culex quinquefasciatus.

The Hawaiian Islands

The Hawaiian Islands

Here’s what one of them looks like!

Culex quinquefasciatus

C. quinquefasciatus.  The parasite is picked up when feeding on the blood of an infected bird.

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What is Avian Malaria?

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

You know that malaria is deadly. But did you know that birds suffer from their own version of the disease? Here are 8 things that everyone needs to know!

Passerines are birds that, like the Red Fody, have a unique foothold that enables them to sit on a perch.

Passerines are birds that, like the Red Fody, have a unique foothold that enables them to sit on a perch. ( Taken from Bahrain bird report (2008), URL: http://www.hawar-islands.com/blog/bugs_stub.php?cat=213)%5B10th November 2014].

  1. It’s a common infectious disease found in wild birds.
  2. The disease mainly affects so-called passerine birds-this includes more than half of all bird species! These birds have three toes pointing forward, and one back like this one above…
  3. Avian malaria is caused by single-celled parasites-Plasmodiumand is spread through the bites of other parasites-mosquitoes (see more in post 3).

Avian malaria has contributed to the extinction of at least 10 native bird species in Hawaii, and threatens many more.

HAWAIIAN HONEYCREEPER (a native forest bird). Avian malaria has contributed to the extinction of at least 10 native bird species in Hawaii, and threatens many more.  Taken from Utah birds (2013), URL: http://www.utahbirds.org/PicOfMonth/Iiwi.htm) [14th November 2014].

4.The disease continues to play a significant role in the decline and extinction of highly susceptible populations i.e. native Hawaiian forest birds (see above).

5. The incidence of this disease has nearly tripled in the last 70 years around the world.

6. Now reports are saying Britain’s birds are suffering from the disease! In fact, there’s actually a good chance that birds visiting your bird feeder are carrying the disease. Yikes! But let me stop the exaggeration. Check out Avian malaria in Europe (pp.69) to find out why the impact of malaria on endemic avian wildlife will be less over here!

7. It does not always appear to affect birds as drastically as the human version affects us. While many birds that carry avian malaria become weak and may eventually die, some individuals can remain healthy (see later posts for further information).

and…

8. Fortunately, humans cannot be infected with avian malaria. Rest assured.

You had me worrying there!

Cor, you had me worrying there. PHEW!

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