Background - Avian Malaria

As I mentioned in the last post my project will investigate the effects of avian malaria on the song of male white-crowned sparrows. There's a couple different aspects to this project and I'll break it out over a few posts:

• Avian Malaria - what is it? How is it spread? What does it do to birds? 
• Bird Song - why do birds sing? What are the effects of parasites on song? 
• White-crowned Sparrows - what are they like? What does their song sound like? Why did I choose this species?
• My Project - what specifically am I going to be doing? What do I expect to find?

Avian Malaria

Avian malaria is similar to human malaria in that it is caused by a protozoan in the genus Plasmodium that is transmitted by mosquitoes. But while human malaria is caused by a handful of Plasmodium species, there are hundreds of species infecting birds. Infections have been documented on every continent except Antarctica.

Upon initial exposure, birds go through an acute phase of infection marked by low energy and high immune system activity. Most species survive this stage but maintain a low-level chronic infection for the rest of their lives. This is both good and bad: good because the birds don't die but bad because they are now perpetually infectious to mosquitoes, continuing the cycle of avian malaria.

Some documented effects include reductions in egg laying, migration ability, and body condition. The most dramatic effects, however, have been on the Hawaiian Islands and with penguins at zoos - in both cases there was widespread mortality.

The picture on the left shows bird blood cells infected with avian malaria. Bird blood cells differ from ours in that they have nuclei. The dark purple ovals are the nuclei and the granulated blotches (highly technical terms here...) are the parasites.
Source: Valkiunas, G. (2005) Avian Malaria Parasites and Other Haemosporidia. CRC Press, Boca Raton, FL