Date: September 5, 2018
Source: American Ornithological Society Publications Office
Animals' lives tend to follow a quicker tempo as they get farther from the equator -- birds at more northern latitudes mature faster, start reproducing younger, and live shorter lives, probably as a way of dealing with seasonal variation in resources. A new study from The Auk: Ornithological Advances shows for the first time that this pattern also plays out in birds' feathers, with northern birds completing their annual molt faster to keep up with the demands of life far from the tropics.
Louisiana State University's Ryan Terrill looked at museum specimens of four bird species with ranges that span a wide swath of latitude in both the Northern and Southern Hemispheres. Slight differences in feather growth between day and night during birds' annual molt produce visible pairs of light-colored bars, each pair representing 24 hours' growth. Terrill could determine the rates at which individual feathers grew by measuring their spacing. He found that for all four species, individuals collected at higher latitudes had grown their feathers faster.