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طيور تنام خلال هجرتها وتحليقها في الجو

رئيس التحرير
2018.04.20 01:08

 

تستطيع طيور «الفرقاطات» أن تنام عميقاً لدقيقة واحدة خلال تحليقها في الجو وذلك لقدرتها على توقيف نشاطها الدماغي بشكل كلي أثناء تحليقها ما يمكنها من النوم عميقاً وفق ما توصل إليه علماء من معهد «زينفيزيني» الألماني بعد مراقبتهم
ويتساءل الكثيرون لماذا تنام طيور الفرقاطات ساعة واحدة فقط في اليوم؟ وكيف تفعل هذا من دون أن تعاني من مشاكل قلة النوم مثل الإنسان ومختلف الحيوانات الأخرى؟
وتمكن نيلز راتنبورغ وفريقه من معهد زينفيزيني في ألمانيا الذي أشرف على هذه الدراسة من حل أحد الألغاز التي تتعلق بهذه الطيور، بعد توصلهم إلى أن طيور الفرقاطات تقبل على النوم لدقائق معدودة خلال تحليقها لأيام متتالية، وذلك بعد مراقبة سلوك وعمل دماغ هذه الطيور التي تتغدى على الأسماك وتقضي معظم أوقات حياتها على السطح المائي للمحيط، باستثناء موسم التكاثر.
وتنقل العلماء إلى أرخبيل «غالاباغوس» مكان مجموعة كبيرة من هذه الطيور، وثبتوا على أجساد مجموعة منها جهازا خاصا يتيح للعلماء قياس مستوى نشاط الدماغ لدى هذه الطيور خلال تحليقها، كما يتيح الجهاز معرفة مكانها، وماذا تفعل خلال رحلتها إلى المحيط الهادئ.
وأظهرت نتائج المراقبة أن طيور «الفرقاطات» قادرة على استقطاع دقيقة من النوم خلال تحليقها، عن طريق إيقافها نشاطها الدماغي بشكل كلي تقريباً في كل مرة ترفعها فيها الرياح إلى الأعلى.

Forget sleep-walking, try sleep-FLYING: Birds can travel for days by snoozing while they are mid-flight

  • On land, birds normally sleep for up to 12 hours a day
  • However, when flying, birds sleep for only a small fraction of this time
  • Birds rest with one half of the brain while the other half remains alert
  • They also keep one eye open to check for obstacles

 

Birds really can sleep while in flight, according to new research.

The strange phenomenon has long been suspected, but scientists at last have the first definitive proof.

They monitored the brainwaves and movements of great frigates from the Galapagos Islands by strapping devices to the heads of females over the course of ten days.

The flight data recorder was attached to frigatebirds - large seabirds that fly continuously in search of fish - for ten days, as they flew a distance of 1864 miles (3000 kilometres)

The flight data recorder was attached to frigatebirds - large seabirds that fly continuously in search of fish - for ten days, as they flew a distance of 1864 miles (3000 kilometres)

UNIHEMISPHERIC SLEEP

At times, the birds went into something known as unihemispheric sleep.

Unihemispheric slow-wave sleep, is the ability to sleep with one half of the brain while the other half remains alert.

This is in contrast to normal sleep for humans and land mammals where both eyes are shut and both halves of the brain show reduced consciousness.

In unihemispheric sleep, activity is seen in one half of the brain consistent with being awake, when examined with an EEG.

This type of sleep usually happened when the birds were circling on rising air currents. They kept the hemisphere connected to the eye that was facing the direction of the turn awake.

Unihemispheric sleep offers a number of benefits, including the ability to rest in areas of high predation or during long migratory flights.

It has been seen in dolphins, seals and walruses, as well as some species of birds. 

Sometimes they were just half asleep with one hemisphere of their brain awake with the respective eye open to watch for potential threats or obstacles.

But at other times the birds were also able to keep both brain hemispheres asleep without crashing.

The research, which is published in Nature, comes from an international team of scientists, led by the Max Planck Institute for Ornithology in Seewiesen, Germany.  

Despite being able to engage in all types of sleep in flight, the birds slept less than an hour a day, a mere fraction of the time spent sleeping on land.

Given the adverse effect sleep loss has on performance, it is commonly assumed that these birds must fulfill their daily need for sleep on the wing.

The researchers suggest that the birds might only switch off half of their brain at a time, to prevent theme from colliding with obstacles or falling from the sky. 

When ducks sleep on the edge of a group, they keep one cererbal hemisphere awake, and the corresponding eye open to look out for potential threats.

Based on these findings, it is commonly assumed that birds also rely on this sort of autopilot to navigate and maintain aerodynamic control during flight.

 

To understand how birds continuously fly, the researchers recorded the changes in brain activity during the two types of sleep found in birds: slow wave sleep (SWS) and rapid eye movement (REM) sleep.

The team developed a small device, known as a flight data recorder, to measure electric changes in brain activity and head movements in flying birds.

The flight data recorder was attached to frigatebirds - large seabirds that fly in search of fish - for ten days, as they continuously flew a distance of 1864 miles (3000 kilometres).

Some birds, including songbirds and seagulls can fly non-stop for several days, weeks, or months as they traverse the globe

Some birds, including songbirds and seagulls can fly non-stop for several days, weeks, or months as they traverse the globe

The results showed that during the day, the birds stayed awake actively searching for foraging opportunities. 

However, at night, the electric signals showed that the birds went into a SWS pattern for periods lasting up to several minutes while they were soaring, in either one or both brain hemispheres.

This suggests that birds are able to maintain aerodynamic control, even when both hemispheres are asleep. 

Looking at the GPS data, the researchers found that when the birds circled, they kept one eye open, suggesting that they were watching where they were going.

Niels Rattenborg, who led the study, said: The frigatebirds may be keeping an eye out for other birds to prevent collisions much like ducks keep an eye out for predators.

As well as SWS sleep, which is light, the birds also went through bouts of REM (deep) sleep, in which their heads dropped momentarily, but their flight pattern remained the same.

While the reasons for sleep deprivation during flight are still unclear, the researchers think that the birds may stay awake to make sure they do not miss good foraging conditions

While the reasons for sleep deprivation during flight are still unclear, the researchers think that the birds may stay awake to make sure they do not miss good foraging conditions

Overall, the results showed that the frigatebirds only slept for 42 minutes a day.

This is surprising, as when they are on land, the birds can sleep for over 12 hours a day. 

While the reasons for sleep deprivation during flight are still unclear, the researchers think that the birds may stay awake to make sure they do not miss good foraging conditions.

The researchers hope to use the findings to determine how birds are able to sustain adaptive performance on such little sleep. 

Mr Rattenborg said: Why we, and many other animals, suffer dramatically from sleep loss whereas some birds are able to perform adaptively on far less sleep, remains a mystery. 

 

كلمة التحرير كتاب واراء مختارات من الصحافة حول العالم لبنان سورية صحة بيئه ابراج نهفة اليوم إعلانات تصويت
هل ترى خطاب التحريض والكراهية وراء تنامي الهجمات المسلحة بالولايات المتحدة؟


القائمة البريدية
البريد الالكتروني

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