Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lopsided feet signal birds’ demise

10.04.2002


Mismatched feet may be a sign of population stress.
© Lens et al.


Asymmetric bodies fuel arguments over ecological risk.

Birds with one foot bigger than the other are showing signs of stress, say Belgian ecologists. The study backs the controversial idea that measuring body asymmetries could signal that a species is at risk.

Researchers at the University of Antwerp measured the feet of taita thrushes from three remaining pockets of their native forest in Kenya. Those from the most disturbed area showed eight times more difference between the size of their left and right feet than the least disturbed - a sign of future decline, they say1.



Yet the discrepancies barely warrant a waddle: "Most of the time, differences between left and right are less than 1% of the trait size itself," says Luc Lens, who led the study. Such small differences fuel an ongoing controversy about the use of asymmetry measures to identify stressed animal populations.

In general, the studies that find a correlation are the ones that get published; those that don’t, rarely make it into print. This issue has given ’fluctuating asymmetry’ a chequered history, with as many sceptics as believers.

Finding the mechanism underlying the disparity will be key to settling the debate. "We’re not at the stage that we understand enough about it and why in some cases it works and others it doesn’t," says conservation biologist Andrew Balmford at the University of Cambridge, UK.

Unbalanced birds

Lens argues that the foot measure in thrushes reveals an indirect link between asymmetry and survival. It is an indicator of a male’s overall quality, he suggests - important to females, who choose the most symmetrical mates. Thus increased asymmetry may imply that a male is less fit. "People wrongly assume that because the differences are so small, the impact or biological relevance is also small," says Lens.

Many who have studied fluctuating asymmetry will not be convinced of its general utility until it can be proven under controlled situations. "When people have examined fluctuating asymmetry and stress in experimental lab conditions, the basic incontrovertible finding is that there is no consistent linkage," argues Andrew Pomiankowski, a geneticist at University College London.

Lens and his colleagues acknowledge that previous work has suffered from confounding measurement errors. But they claim to have developed new statistical methods that accurately separate variation caused by asymmetry from measurement error.

Pomiankowski agrees that for this particular trait in this species, Lens and his group may have found a real difference, but that it can’t be assumed to work elsewhere. It will have to be determined on a case by case study, says Pomiankowski - there is no universal trait that will indicate an individual’s fitness.

Asymmetry measures might be most useful if they could pick up insidious, hard-to-detect threats, suggests Balmford, such as the spread of disease, rather than stresses resulting from habitat decline. There are about 1,350 thrushes in the region studied by Lens, but the most degraded area has a declining population and the fewest individuals.

References

  1. Lens, L., Van Dongen, S. & Matthysen, E. Fluctuation asymmetry as an early warning system in the critically endangered taita trush. Conservation Biology, 16, 479 - 487, (2002).


VIRGINIA GEWIN | © Nature News Service

More articles from Ecology, The Environment and Conservation:

nachricht Surface clean-up technology won't solve ocean plastic problem
04.08.2020 | University of Exeter

nachricht Improving the monitoring of ship emissions
03.08.2020 | Carl von Ossietzky-Universität Oldenburg

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: ScanCut project completed: laser cutting enables more intricate plug connector designs

Scientists at the Fraunhofer Institute for Laser Technology ILT have come up with a striking new addition to contact stamping technologies in the ERDF research project ScanCut. In collaboration with industry partners from North Rhine-Westphalia, the Aachen-based team of researchers developed a hybrid manufacturing process for the laser cutting of thin-walled metal strips. This new process makes it possible to fabricate even the tiniest details of contact parts in an eco-friendly, high-precision and efficient manner.

Plug connectors are tiny and, at first glance, unremarkable – yet modern vehicles would be unable to function without them. Several thousand plug connectors...

Im Focus: New Strategy Against Osteoporosis

An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.

Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...

Im Focus: AI & single-cell genomics

New software predicts cell fate

Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Rare Earth Elements in Norwegian Fjords?

06.08.2020 | Earth Sciences

Anode material for safe batteries with a long cycle life

06.08.2020 | Power and Electrical Engineering

Turning carbon dioxide into liquid fuel

06.08.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>