In Wieringermeer, a typical Dutch polder that was reclaimed from the sea in 1930, Bewick’s swans stop by during migration to feed on the leftovers of sugarbeets that remain after the farmer’s harvest. The ornithologists were interested in why some fields were used more intensively than others, while all fields seem to offer similar amounts of food right from the start.
They wondered: "In case foraging benefits seem to be equal across all fields, there may be variation in foraging costs that may explain the observed spatial heterogeneity in exploitation." The authors showed, in the May issue of the American Naturalist, that the time spent feeding on a field by a flock of swans can be used as a surrogate of an individual’s energy intake rate (which declines over time due to depletion). This showed that an individual’s intake rate at abandoning a field, which should reflect the foraging cost as experienced by the bird itself, decreased with the distance to roads and increased with the distance to its nighttime roost.
The higher intake rates at which fields near roads were given up reflected the chance to be disturbed by humans. The higher intake rates at which fields far from roosts were given up could be explained by the energetic cost of flight, which are substantial for large birds such as Bewick’s swans. When taking these flight costs into account, the authors calculated that the net benefits at which each field was given up corresponded with the net benefits obtained in the long run. The latter was measured via regular visual inspection of the thickness of each bird’s belly!
All these insights into foraging costs could be implemented into a model that predicted the number of swans that potentially could stop by at the site. This model accurately and correctly predicted the true number of birds that made use of the stopover. It could thus serve as a valuable tool to manage and protect the relatively small population of Bewick’s swans wintering in NW Europe, which declined from 30,000 to 20,000 birds over the last 15 years.
Patricia Morse | EurekAlert!
Successful calculation of human and natural influence on cloud formation
04.11.2016 | Goethe-Universität Frankfurt am Main
Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Power and Electrical Engineering
07.12.2016 | Health and Medicine
07.12.2016 | Life Sciences