The latest symptom of climate change has wriggled onto the radar of a team of WCS researchers.

In northeastern Argentina, an increasingly muggy climate is creating better conditions for fly larva to infect baby birds. In a recent study, WCS field veterinarians and biologists found an elevated number of parasitic maggots of Philornis torquans burrowing into the skin of more than 20 species of nesting chicks. Being large in comparison to their unfortunate hosts, the parasites can sometimes kill the birds or cause them to grow abnormally.  

“Although ours is a short-term study looking at within-year variability, we clearly show that higher temperature and precipitation result in greater parasitic fly loads. This is a striking example of the kind of negative effects on wildlife that can arise as a result of climate change,” said Dr. Pablo Beldomenico of WCS’s Global Health Program. “The greater precipitation and warmer weather predicted for some areas of South America could have a significant impact on native birds because of a large increase in parasites like these.”

During two consecutive austral summers, the scientists examined the prevalence of the fly among the area’s bird community. They found a positive correlation between temperature and rainfall levels and the amount of parasites affecting nestlings. Of the 41 bird species studies, 4 species—the great kiskadee, the greater thornbird, the little thornbird, and the freckle-breasted thornbird—were the most prone to having the telltale bulges on their heads, bodies, and wings of the underlying larva.

The more parasites the young birds had, the higher the chance the chick would die. The research found that a bird with 10 larvae was twice as likely to die compared with a chick that was parasite-free. More heavily parasite-laden chicks also grew at slower rates. The scientists observed one poor chick that had 47 larvae on its body.  

“Understanding how environmental factors influence the health of wildlife populations, and how this is changing in response to climate change, will help inform strategies to mitigate its deleterious effects,” said Dr. Paul Calle, WCS’s Director of Zoological Health.