Researchers from the University of Oklahoma and the Sutton Avian Research Center in Bartlesville have found evidence that severe storms have caused a physical change in a population of birds.
The team studied Grasshopper Sparrows near El Reno, OK. The birds survived a massive storm in May 2013. It was a deluge that saw a 2-mile wide EF5 tornado and hailstones that were more than two inches wide. The birds they studied were born just before the storm. You can read the study here.
Dr. Jeremy Ross in the field during study.
Dr. Jeremy Ross was the lead researcher. He reports they found a spike in the chemical signature of what’s called pallid bands in the tail feathers of the birds. Dr. Ross says the bands contained more of a certain type of nitrogen isotope. He says the stress of living through the storm caused muscle tissue to break down which changed the composition of the nitrogen in the blood. That change plays itself out as the feathers develop. “This may be the first example of severe thunderstorms being scientifically implicated in sublethal stress impacts on wildlife,” says Dr. Ross.
Pallid band on the tail feather of a young Grasshopper Sparrow. Photo courtesy: W. Alice Boyle
So why would this happen? What’s it mean? Dr. Ross says the tail is less important than the wing feathers in young birds. During high-stress events, like severe storms, food can be harder to find because the hailstones can kill either one or both parents of the fledgling or kill the insects on which they feed. When that happens the body moves blood from growing feathers that are not as important in order to protect other parts of the body that need more blood and energy.
Dr. Ross say it’s not unusual for Grasshopper Sparrows to have pallid bands but it’s normally about 2% of the population. After the El Reno storm they discovered about 44% of the population showed the pallid bands.
A detailed look at the Pallid Bands in the tail feathers of young Grasshopper Sparrows. Photo courtesy: W. Alice Boyle
The study came about by accident, Dr. Ross says the team was doing other research in the area when they noticed the high rate of pallid bands in the Grasshopper Sparrows. (What a great example of how fluid science can be!!) Dr. Ross told me, “This study represents the opportune accident that scientists often don’t plan for and, therefore, don’t report. We have encouraged the scientific community to follow suit and report such findings because as a connected network we can be assured that in any given year severe weather will strike an existing field study. From such events we can gain insight into what the impacts of current severe weather patterns are now and, from this insight, we can start to predict how intensifying and expanding severe weather patterns will impact wildlife populations under a changing climate.”