Navigation Links
MIT solves gravity-defying bird beak mystery
Date:5/15/2008

CAMBRIDGE, Mass.--As Charles Darwin showed nearly 150 years ago, bird beaks are exquisitely adapted to the birds' feeding strategy. A team of MIT mathematicians and engineers has now explained exactly how some shorebirds use their long, thin beaks to defy gravity and transport food into their mouths.

The phalarope, commonly found in western North America, takes advantage of surface interactions between its beak and water droplets to propel bits of food from the tip of its long beak to its mouth, the research team reports in the May 16 issue of Science.

These surface interactions depend on the chemical properties of the liquid involved, so phalaropes and about 20 other birds species that use this mechanism are extremely sensitive to anything that contaminates the water surface, especially detergents or oil.

Some species rely exclusively on this feeding mechanism, and so are extremely vulnerable to oil spills, said John Bush, MIT associate professor of applied mathematics and senior author of the paper.

Wildlife biologists have long noted the unusual feeding behavior of phalaropes, which spin in circles on the water, creating a vortex that sweeps small crustaceans up to the surface, just like tea leaves in a swirling tea cup.

The birds peck at the surface, picking up millimetric droplets of water with their prey trapped inside. Since the birds point their beaks downward during the feeding process, gravity must be overcome to get those droplets from the tip of the bird's long beak to its mouth. Until now, scientists have been puzzled as to how that happens.

Scientists speculated that the feeding strategy depended on the drop's surface tension. Surface tension normally dominates fluid systems that are small relative to raindrops (for example, the world of insects), but it was not clear how it could benefit shorebirds. A key observation was that in order to propel the drop, the birds open and close their beaks in a tweezering motion.

To unravel the mystery, Bush teamed up with Manu Prakash, a graduate student in MIT's Center for Bits and Atoms, and David Quere, of the Ecole Polytechnique in Paris, a visiting professor in MIT's math department at the time of the study. They built a mechanical model of the phalarope beak that allowed them to study the process in slow motion.

The process depends on a surface interaction known as contact angle hysteresis, typically an impediment to drop motion on solids. For example, raindrops stick to window panes due to contact angle hysteresis. In the case of the bird beak, the time-dependent beak geometry couples with contact angle hysteresis to propel the drop upward.

This may be the first known example where droplet motion is enabled rather than resisted by contact angle hysteresis, Bush said.

As the beak scissors open and shut, each movement propels the water droplet one step closer to the bird's mouth. Specifically, when the beak closes, the drop's leading edge proceeds toward the mouth, while the trailing edge stays put. When the beak opens, the leading edge stays in place while the trailing edge recedes toward the mouth.

In this stepwise ratcheting fashion, the drop travels along the beak at a speed of about 1 meter per second.

The efficiency of the process, which the authors dub the capillary ratchet, depends on the beak shape: Long, narrow beaks are best suited to this mode of feeding. The study highlights the sensitivity of this mechanism to the opening and closing angles of the beak: Varying these angles by a few degrees can change the drop speed by a factor of 10, Quere said.

The capillary ratchet also depends critically on the beak's wettability--a measure of a liquid's tendency to bead up into droplets or spread out to wet its surface. Oil is much more wetting than water, so if the beak is soaked in oil from a spill, this process won't work.

The researchers note a potential application of nature's design: We are currently exploring microfluidic devices in which this mechanism could be exploited for directed droplet transport, allowing for controlled stepwise motion of microliter droplets, Prakash said.


'/>"/>

Contact: Elizabeth Thomson
thomson@mit.edu
617-258-5402
Massachusetts Institute of Technology
Source:Eurekalert

Related biology news :

1. JILA solves problem of quantum dot blinking
2. Magnetic snakes control fluids, gravity-defying droplets, and solving a dragonfly mystery
3. Scientists tackle mystery mountain illness
4. Folate mystery finally solved
5. Men shed light on the mystery of human longevity, study finds
6. Cassini on the trail of a runaway mystery
7. Time-sharing tropical birds key to evolutionary mystery
8. 480-million-year-old fossil sheds light on 150-year-old paleontological mystery
9. ASU professor helps solve mystery of glassy water
10. Ancient mystery solved
11. UCLA researchers solve decade-old mystery
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/18/2016)... , Jan. 18, 2016  Extenua Inc., ... that simplifies the use and access of ubiquitous ... go-to-market partnership with American Cyber.  ... extensive experience leading transformational C4ISR and Cyber initiatives ... integrating the latest proven technology solutions," said ...
(Date:1/13/2016)... January 13, 2016 --> ... a new market report titled - Biometric Sensors Market - ... 2015 - 2023. According to the report, the global biometric sensors ... anticipated to reach US$1,625.8 mn by 2023, expanding at ... terms of volume, the biometric sensors market is expected ...
(Date:1/11/2016)... , Jan. 11, 2016 Synaptics Incorporated ... interface solutions, today announced that its ClearPad ® ... (TDDI) products won two separate categories in the 8 ... Innovator and Best Technology Breakthrough. The Synaptics ® ... a simplified supply chain, thinner devices, brighter displays and ...
Breaking Biology News(10 mins):
(Date:2/4/2016)... SHENZHEN, China , Feb. 4, 2016 ... government, and various medical institutions attended a ceremony in ... provide integrative, personalized cell therapy in 2016. ... the "Shenzhen Clinical Translation Platform for Personalized Cell Therapy" ... Shenzhen Regional Cell Production Center, both subsidiaries of Beike ...
(Date:2/4/2016)...  Spherix Incorporated (Nasdaq: SPEX ) -- an intellectual property ... intellectual property, today provided an update on the Company,s ... of Texas and announcing that ... Partes Re-examination ("IPR") proceedings that VTech and Uniden ... initiated on only certain claims of two of the ...
(Date:2/3/2016)... DIEGO , Feb. 3, 2016   ... company with the first pluripotent stem cell-derived islet ... diabetes in clinical-stage development, today announced that ViaCyte ... Pharmaceutical Companies of Johnson & Johnson, have agreed ... group into ViaCyte.  The agreement provides ViaCyte with ...
(Date:2/3/2016)... BRUNSWICK, N.J. , Feb. 3, 2016 /PRNewswire-USNewswire/ ... grants totaling more than $1 million for researchers ... are working on health-related research that demonstrates exciting ... this round of funding for the New Jersey ... for faculty members at these educational institutions— Princeton ...
Breaking Biology Technology: