For the first time, we can rule out the earth as the most significant source of climate change. We don’t know where it came from. But the culprit may be a familiar place: the bird population.
According to a new study published this week in Biology Letters, the social pressures of migrating birds can contribute to obesity among the flocks they travel with. This hypothesis offers a powerful proof for the hypothesis that climate change effects climate change.
The study, which draws on detailed images of the resting habits of wintering American nuthatches, found that the flocks created by the smaller birds often came from a mix of weak-bodied species that require little time to recover after rest, rather than the larger bird that conserves energy in colder weather. Compared to the average bird in the winter, the flocks were on average 10 percent smaller and significantly slimmer.
This may be by design. Walking in what looks like a spring fling may require less effort. The closer the flocks came to the land’s surface — during active breeding seasons or during migration — the smaller the birds. More compact, smaller birds presumably can slow down for longer.
There’s a long and complicated history of researchers exploring the mechanisms of migrating birds to better understand climate change effects. Migratory behavior researchers have understood for decades that effects of more rapid climate change and other environmental changes can create unique dynamics in the flocks they travel with. Only recently have scientists begun to experiment with counting individual flocks to measure the relationship between climate change and species.
Compared to studies on continents miles apart, and particularly the Arctic, the Little Neck Bowl, a breeding ground for American nuthatches in eastern England, is a relatively accessible place. Those involved in the study were able to properly measure the flocks using a variety of imaging techniques, including spectroscopy, infrared tracking, telemetry, and photographs.
A half-dozen different variables can affect a flocks’ health, weight, and healthiness: biological characteristics such as the density of a flock’s bird populations, whether it’s difficult to produce offspring, and other environmental factors such as temperature and rainfall. Some of the results of the Little Neck Bowl study are far from conclusive, though: “Perhaps other factors are exerting less influence than we think,” lead researcher Ruth Deakin of the University of Lincoln in England writes in a release.
Deakin points out that previous studies have pointed to growing environmental pressures around the world, which may contribute to individual birds either being unable to or choosing not to store energy as they migrate.
She also points out the limitations of understanding bird populations from a study of merely a single breeding ground.
Still, the implications for birds and other species that live on the world’s crowded borders seem far-reaching.
“We do not yet understand well enough the big picture story about avian species and climate change and our study provides a compelling window into the possible nature of those effects,” Deakin writes.