Seabirds always know where they are and how to get 'home' thanks to innate navigation ability – but can't remember landmarks or obstacles
- Scientists tracked more than 700 Manx shearwaters, which are native to Britain
- The birds could direct themselves home but forgot about obstacles on the route
- They ended up flying around them multiple times, making their flights longer
- But they were able to plan ahead and leave early if they had further to go
Seabirds can remember the distance and time they have to travel to get home, but forget the landmarks along the way, research has revealed.
A study of Manx shearwaters, which live off the west coast of England, Scotland and Wales, found they didn't seem to remember obstacles.
Among these obstacles were bodies of land such as islands and peninsulas, which the birds refused to fly over so had to navigate their way around.
Researchers led by the University of Oxford tracked the flights of birds called Max shearwaters which fly, sometimes more than 100 miles, over the ocean to look for food (stock image)
Researchers from University of Oxford tracked the flight paths of 707 of the small birds, which weigh around 0.8lbs (400g) each.
The birds flew on trips to forage for food and would sometimes range more than 100 miles away from their colonies.
At the beginning of their return journey, the birds tended to be 'well oriented', the scientists found.
They seemed to be able to organise themselves, leaving earlier if they had further to travel, and could point themselves in the right direction from the start.
But, the researchers wrote in their paper: '[The shearwaters] often fail to encode intervening barriers over which they will not fly, constrained to flying farther as a result.
The Manx shearwaters the scientists tracked were able to orient themselves in the right direction every time but didn't seem to remember deviations on the route to go around islands
'Second, shearwaters time their homing journeys, leaving earlier in the day when they have farther to go, and this ability to judge distance home also apparently ignores intervening obstacles.'
The shearwaters would refuse to fly over bodies of land – such as islands or peninsulas – for a long time, the researchers said.
Therefore, they would fly in a straight line until encountering one of these, then – because they had not remembered it was there – fly around it.
This would make the birds' journeys longer than they had intended.
Based on their study, the scientists suggested the birds could either try to remember basic maps of their local area, or that they found their way home by thinking about the angles of how they rotated their bodies on the way somewhere.
The researchers, led by Dr Oliver Padget, wrote: 'First, perhaps least likely, is the possibility that they have formed through previous experience a large-scale familiar area map encoding the unique features of remote locations from which they have homed before...
'However, this would essentially require memorizing information pertaining
to routes that had not actually been experienced, so it is unclear what learning mechanism could achieve this.
'The second possibility is that the birds, like ants, use path integration to compute a running egocentric homing vector by registering the rotations and translations that they experience on their outward journey, which would naturally be blind to obstacles in the homing path.'
The team said theirs is some of the most detailed evidence to date of how seabirds navigate their way around.
Their research was published in the journal Proceedings of the National Academy of Sciences (PNAS).
WHAT IS THE EARTH'S MAGNETIC FIELD AND HOW DO BIRDS USE IT?
Scientists believe the Earth's core is responsible for creating its magnetic field which is a force created by moving electrical charges.
As molten iron in the Earth's outer core escapes it creates convection currents. These currents generate electric currents which create the magnetic field.
This is a natural process known as a geodynamo.
This creates a geomagnetic field that extends from the interior of the Earth to where it meets the solar wind, which is charged particles coming from the sun.
Birds use this magnetic field to plot their migratory routes. This has often been called their 'sixth sense'.
For a bird to know roughly where it is in the world – and correct itself if it goes off course – it needs what is known as ‘true navigation’.
This means it can somehow work out its latitude and longitude.
For humans, the problem of longitude - the co-ordinate that specifies an east-west axis position on the Earth’s surface - proved unresolvable until the invention of accurate clocks.
For a bird to know roughly where it is in the world – and correct itself if it goes off course – it needs what is known as 'true navigation'. The Earth's magnetic field (stock image) is pictured
The North and South magnetic poles are generally located near the geographic poles. However, they vary over geological time and once every several hundred thousand years they flip.
While a compass needle points to the magnetic north, this is not the true north – the North Pole.
Depending on where you are, magnetic north is either one or more degrees further east or west of the north pole.
New research suggests birds rely on a protein in their eyes that means they can 'see' Earth's magnetic field and this stream of charged particles.
Scientists from Lund University in Sweden looked at zebra finches, while researchers from Carl von Ossietzky University Oldenburg in Germany studied European robins.
According to researchers a protein called Cry4, which is present 24 hours a day and means birds can still navigate during night, is responsible for this.
This means they can 'see' these magnetic fields over their normal vision.
Researchers also found European robins had increased Cry4 expression during the migratory season.