It is hard to think of too many downsides to birds, but there are some and here I’d like to mention one that we all know about but has been recently studied more closely. The results of this research paper appear in the Journal of Zoology.

You know that birds carry various parasites in their blood, and often, these parasites are transmitted to and from the birds via ticks or other ectoparasites. It is probably the case that the rapid spread of Lyme Disease from Connecticut to the rest of the United States and adjoining regions of Canada was because some species of birds (but not all) can carry Lyme disease, and can also carry the ticks that carry the disease.

Here’s the abstract from this recent paper:

Blood parasites are often considered as indicators of immunity in birds, and data on parasite prevalence and intensity of infections are essential to reveal information about the condition of both individuals and populations. We prevented parasite vectors from biting and infecting nestling great tit Parus major by using insect repellent inside nest boxes. We found that in the absence of blood parasites, great tit nestlings had higher concentrations of haemoglobin, and they survived at signi?cantly higher rates through the nestling phase and also during the ?rst weeks of their ?edgling period. This is the ?rst demonstration so far of the impact these parasites have on haemoglobin levels of the hosts, which reveals one mechanism of adverse impact by blood parasites. This study shows that the effects of blood parasites can be assessed without using anti-malaria drugs, which can cause additional risk of oxidative stress.

To me, this an interesting fact wrapped in language about a somewhat esoteric research program involving malaria and stuff. Here’s the part that I find interesting. When you get rid of the blood parasites, the nestlings survived at significantly higher rates. How much higher? This much higher:

Wow

Wow

A lot has been made of honest advertising of quality in birds and other animals. The idea is this: Add some ridiculous debilitating feature or carry out some absurd energy demanding behavior and see how you do. If it slows you down or wears you out, that could be because you are sick, or perhaps just by chance you somehow ended up at the short end of the gene pool. A potential mate will notice this and skip over you to find a different partner.

Birds are famous for their mating displays, rituals, coloration, vocalization, and so on and so forth. These are all things that demand physical stamina or otherwise well operating physiological systems, which are not likely to be the case if one is loaded up with too many parasites. Too many parasites also reduce reproductive output.

This is stuff we all already knew, or at least strongly suspected and occasionally saw evidence of. This study shows a huge difference in nestling survival with a change (albeit a significant change) in parasite load, and thus, is an excellent example of the importance of assessing parasite load or other health related issues for birds.

The paper is:

Krams, et al. 2013. Tackling Blood Parasites Helps Birds Survive Avian Malaria. Journal of Zoology. Link

Photo of Great Tit by Corey

Written by Greg
Greg Laden has been watching birds since they were still dinosaurs, but has remained the consummate amateur. This is probably because he needs better binoculars. Based in the Twin Cities, Minnesota, Greg is a biological anthropologist and Africanist, who writes and teaches about Evolution, especially of humans. He also blogs at Scienceblogs.com. Greg's beat is Bird Evolutionary Biology. One could say that knowing the science of birds can make the birds more interesting. But really, knowing about the birds that go with the science is more likely to make the science more interesting. And thus, birding and Neo Darwinian Theory go hand in hand. Darwin was, after all, a pretty serious birder. Greg has seen a bird eat a monkey in the wild.