Wednesday, July 1, 2015

Birds flee long before the arrival of the storm

Birds flee long before the arrival of the storm
Some birds feel severe storms days in advance severe storms make noise in the infrasonic range over hundreds of kilometers away. Some birds will not concealed, researchers have found. This capability saves their lives. Thanks to its biological early warning to flee gold-winged Warbler long before the arrival of tornadoes. Some birds feel enlist severe storms and flee one to two days in advance. Apparently possessed the gold-winged Warbler on an early warning system that will respond to the infrasound of storms, report US researchers in the journal "Current Biology".

The scientists from the University of California Henry Streby had made their discovery by accident: Actually, they wanted to test whether only a few grams predominant birds are able to wear tracking device.

But then the animals suddenly flew them: One or two days before a huge storm hit the end of April 2014 Southeast Coast of the US, they left their breeding grounds in the state of Tennessee - where they had just arrived. During the storm 84 tornadoes were counted, 35 people died.

Birds flee long before the arrival of the storm
The gold-winged Warbler (Vermivora chrysoptera) flew in five days at least 1,500 kilometers to escape the storm - and finally arrived at the coast of the Gulf of Mexico. "The amazing thing is that the birds departed long before the arrival of the storm," said Streby in a release about the study.

"At the same time, as we said the meteorologists the weather channel that the storm is coming in our direction, the birds made ready to leave the area." At that time, the storm was still 400 to 900 kilometers from the breeding grounds. Also there were no changes in air pressure, temperature or wind speed.

The researchers suspect that the animals hear the infrasound approaching storm. "Meteorologists and physicists have long known that tornado storms produce strong infrasound, which extends thousands of kilometers," Streby executes. This sound is a frequency below about 16 to 20 Hertz for the human ear does not hear, but it is exactly in the frequency range, best perceive the birds.

In 2000, the US geophysicist Jon Hagstrum had demonstrated that the infrasound of the supersonic aircraft Concorde prevents pigeons from finding their way home. Hagstrum, who was not involved in the current study, says now: "Acoustics for birds could generally be an important tool to assess their environment - so how dogs use smells and people their sight."

Breeding area is not normally leave
Is already known that migratory birds change their routes if required by the weather. "Until our study, however, was never observed that birds leave their breeding grounds due to weather conditions, if their journey is actually already completed," said Streby.

Straight from Gold Wing warblers know you, they actually remain in place, once they have reached their breeding area to raise their chicks. The animals from the family of Warbler (Parulidae) breed in eastern North America and southern Canada. In winter, the songbirds move to Central and South America, very rarely they have also been spotted in Western Europe.

The realization of US scientists is particularly important in view of the fact that is expected due to climate change with more severe storms. Then threatened disadvantages: "This behavior will cost the birds probably energy and time they needed for reproduction," said Streby.

In a new project, the team now wants to equip hundreds of warblers with tracking devices to find out exactly where the birds spend the winter and which route they use there and back again. Streby said: "I hope not to a severe tornado season, but I'm curious to see what unexpected things we observe this time."

Which creature can feel what what?
About her nose and her mouth come the bats from high-frequency cries. The emitted sound waves (red) propagate in space and encounter an insect. There, the sound waves are reflected and move as changing sound waves back to the ear of the bat (blue). The fluted ear picks up the echo: acoustic waves from above hit the ear at a different location than sound waves from below. Based on the reflected echoes detects the bat shape, size, location and direction of movement of the insect. Now they can still snatch their prey in flight.

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