Photo credit
Tree swallows’ iridescent feathers change from blue-green to muted yellow when exposed to humidity. The plumage reverses to previous color tones as humidity decreases.
This discovery by Chad Eliason, a University of Akron integrated bioscience Ph.D. program student, and Dr. Matthew Shawkey, assistant professor of biology and integrated bioscience, is published in the Sept. 27 issue of Optics Express, the international journal of optics.
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Rapid, reversible response of iridescent feather color to ambient humidity
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(PhysOrg.com) — A new study of pigeons shows that, like human gamblers, they love to gamble on the off chance they will win big rather than taking a smaller, but more certain payout.
Research by psychologists Thomas Zentall and Jessica Stagner of the University of Kentucky in Lexington found pigeons given a choice of a light that would deliver three pellets of food every time or one that gave them a big “win” of 10 pellets 20 percent of the time consistently chose the latter. When averaged out, these results meant the pigeons were preferring a payout of two pellets for each peck rather than three.
The researchers trained eight pigeons to peck at keys that caused a vertical or horizontal light to be displayed on a screen in yellow, blue, red or green colors. In return they received food rewards. If they pecked at the key that presented a horizontal line (yellow or blue) three food pellets were dispensed each time, which therefore represented a non-gambling option. If they pecked on the key for the vertical line, it was one color (say green) 80 percent of the time, in which case no food was delivered. The remaining 20 percent of the time the line was the signal color (say red), in which case 10 pellets were dispensed. The vertical line therefore represented a gambling option. (Color combinations were changed for different birds to avoid any bias.)
After Zentall and Stagner had trained the birds to understand what the lines and colors meant they then carried out many trials to see which the birds preferred. The results were that the pigeons chose the riskier 10 pellets or nothing option in over 80 percent of the trials, even though on average they would receive 50 percent more food if they chose the other option.
In a later experiment they trained seven new pigeons, but this time both red and green colors triggered the release of 10 pellets 20 percent of the time and nothing the rest of the time. The yellow and blue colors still resulted in three pellets being released. In this case the pigeons chose the yellow/blue option for a sure payout of three pellets.
Zentall said the findings suggest the pigeons in the first trials put excess weight on the excitement on the windfall that resulted from a red light, and evening out the odds on red and green detracted from the excitement. He commented that in human gambling watching a winning pattern appear on a slot machine, for example, precedes winning the money, and suggested gamblers would not wager as often if there were no signals for their winning — so slot machine players could not see the wheels, and roulette players could not see the ball.
Zentall said if the pigeons were hungry they tended to gamble more than if they were already satisfied, despite having more to lose, and this has parallels in human gambling studies, which have shown that people who are dissatisfied with their lives and have less money tend to gamble more than those who are wealthier and more satisfied.
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Maladaptive choice behaviour by pigeons: an animal analogue and possible mechanism for gambling (sub-optimal human decision-making behaviour)
Vultures use Face Flushing Technique for Instant Status Updates
Tech savvy humans who use social media sites to instantly update their ‘statuses’, may be behaving like vultures who use ‘face flushing’ as a visible way of instantly updating their own status when interacting with peers and rivals. Research, published in Ethology, reveals how the ability to rapidly change skin colour is a key form of interaction for vultures, especially for displays of dominance.
The ability to rapidly change skin colour has been well documented in reptiles and fish, which use specialist cells to disperse and concentrate pigments. However, the ability can also be found in some mammals and bird species which exhibit bare skin, such as the vulture.
“Vultures have un-feathered sections of skin on their heads which can become bright red when blood flow is increased, a technique known as flushing,” said Dr Andrew Bamford from Nottingham University. “The advantage in using their bare skin as a signal is that colour changes can occur more rapidly than in feathers or fur, provide up-to-date information on status.”
Dr Bamford and co-authors studied Lappet-faced vultures, Aegypius tracheliotos in northern Namibia to discover how this face flushing ability is used. The team placed food at spots where vultures are known to gather at sunrise and monitored the wild birds’ interactions.
The team found that adults with flushed heads won the majority of social interactions against adults with pale heads and juveniles. However, adults with pale heads were not successful against juveniles.
The team also discovered that a previously unnoticed blue colouration also has an impact on the outcome of interactions. Adults with blue throats won the majority of their interactions with pale or red throated individuals.
“Our study has shown colouration correlates with the outcome of interactions in gatherings of lappet-faced vultures,” concluded Bamford. “Previously interaction was thought to depend on aggressive behavior, but face flushing status plays an important part in the initiation of, and response to, interaction from other vultures.” source
