In order to stay warm on frigid winter days, small birds may do more than just fluff up their feathers. According to new research, they're actually able to make their blood run hotter, creating a sort of central heating system.
In a recent study conducted by Sweden's Lund University and Scotland's University of Glasgow, scientists took blood samples from great tits, coal tits and blue tits, both in early autumn and in late winter. The researchers isolated red blood cells from those samples, then observed the mitochondria activity within those cells.
Mitochondria are subcellular structures that can produce either muscle energy or heat. Utilizing an instrument known as a respirometer, the scientists were able to ascertain how much oxygen the birds' mitochondria were consuming, which in turn allowed them to determine if the mitochondria were generating energy or heat.
It was found that in the winter, the mitochondria were used more to produce heat – this was somewhat unexpected, since it has long been assumed that small birds have a higher metabolism in the winter, which would require a greater expenditure of physical energy. Additionally, it was observed that in the winter, there were greater numbers of mitochondria within the red blood cells.
"We had no idea that the birds could regulate their blood as a heating system in this way, so we were surprised", says the lead scientist, Lund's Assoc. Prof. Andreas Nord.
The team now plans on investigating whether the winter weather itself triggers the change in mitochondrial function, or if it may be caused by factors such as seasonal changes in diet.
A paper on the research was recently published in The FASEB Journal.
Source: Lund University