Pigeons might not have compasses in their beaks after all, according to a new study.
A team of European and Australian researchers published a paper in Nature this week that looked at how pigeons used their beaks as compasses to navigate.
Pigeons, especially homing pigeons, are renowned for their ability to navigate long distances without getting lost. Researchers have long thought that they can do so with an internal compass that lets them sense the Earth’s magnetic field, and recently theorized that this compass was in the birds’ beaks.
Specifically, explains study co-author Johannes Riegler, scientists thought there were clusters of neurons at six specific sites in the beak linked to iron-rich particles. Those particles would shift based on the Earth’s magnetic fields, triggering the neurons and giving the bird a read on magnetic north.
Using coloured dyes, MRI scanners and electron microscopes, Riegler and his team examined the heads of about 200 rock pigeons to try and find these particles. They found them, but they were all over the place rather than in specific spots, and weren’t in cells that could trigger neurons.
Riegler said they found that essentially all the iron is in macrophages: white blood cells that eat dead cells, recycle iron and do not produce signals that trigger neurons. This suggests that the current “beak compass” theory probably isn’t true.
Roland Zacharias, who breeds racing homing pigeons near Cardiff, said he was skeptical of the compass theory as well.
He suspected the sun was a more important factor.
“If you take [pigeons] to a release point … the first thing they’ll do is start looking and spotting where the sun is.”
They also zip off almost instantly on sunny days, he continues, but circle for several minutes when it’s cloudy.
Pigeons have an incredibly accurate internal clock, Zacharias noted – they always lay their first eggs each spring within 10 minutes of 7 p.m. – and could use their memory of where the sun should be at any one time to navigate. Other breeders suspect the birds use landmarks, sounds or smells. “My theory is they have all kinds of backup systems.”
Does holding a gun make you a bigger man? Yes, suggests a recent study – about 5.82 centimetres bigger, to be exact.
Researchers from the University of California, Los Angeles, published a paper this week in the online journal PLoS ONE on how holding a weapon makes people seem taller and more muscular. This study is part of a larger study by the U.S. Air Force on how people make decisions in potentially violent situations, and is thought to have implications for police and the military.
When confronted by an opponent, explained Daniel Fessler, an anthropologist at UCLA and lead author on the study, people have to quickly evaluate their chances of victory. Since the actual outcome depends on any number of factors (skill, weaponry, etc.), his team theorized that humans might have evolved a shorthand for these factors to speed up their decisions, specifically, bigness.
Fessler and his team had about 628 people look at pictures of male hands holding one of four objects: a caulking gun, an electric drill, a hand saw and a .357 magnum. The volunteers were then asked to guess the height and musculature of the person holding the object.
The team found that people judged the person holding the gun to be about 17 per cent taller and stronger than the person holding the caulking gun – the gunman was pegged at 1.77 metres tall on average, while the caulker averaged 1.72 metres.
The team had similar results during a separate trial with a kitchen knife, squirt gun and paintbrush. There, knife-holders were judged to be the tallest and most muscular, suggesting that the perceived lethality of the object, rather than cultural norms associated with guns, was the key factor.
“There’s nothing about the knowledge that gun powder makes lead bullets fly through the air at damage-causing speeds that should make you think that a gun-bearer is bigger or stronger, yet you do,” he said. “Danger really does loom large, in our minds.”
Fessler said this shorthand might be a holdover from the days where physical size was the main determinant in a fight’s outcome. This isn’t necessarily a good or bad thing, he explained, it’s the violence that can result that is the problem.
