Learn About Homing Pigeons

In this episode of the I Can't Sleep Podcast, fall asleep learning about homing pigeons. Yeah, I'm so bored with thinking about writing something about homing pigeons that I'm just going to leave it like this. Happy sleeping!

Transcript

Welcome to the I Can't Sleep podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster.

Today's episode is from a Wikipedia article titled,

Homing Pigeon.

The homing pigeon,

Also called the male pigeon or messenger pigeon,

Is a variety of domestic pigeons derived from the wild rock dove,

Selectively bred for its ability to find its way home over extremely long distances.

The rock dove has an innate homing ability,

Meaning that it will generally return to its nest using magnetoreception.

Flights as long as 1,

800 kilometers have been recorded by birds in competitive pigeon racing.

Their average flying speed over moderate 965 kilometer distances is around 97 kilometers an hour,

And speeds of up to 160 kilometers an hour have been observed in top racers for short distances.

Because of this skill,

Domesticated pigeons were used to carry messages as messenger pigeons.

They are usually referred to as pigeon post,

If used in post service or war pigeon during wars.

Until the introduction of telephones,

Homing pigeons were used commercially to deliver communication.

Messenger pigeons are often incorrectly categorized as English carrier pigeons,

An ancient breed of fancy pigeons.

They were used historically to send messages,

But lost the homing instinct long ago.

Modern day homing pigeons,

Homers,

Or racing pigeons,

Racing homers,

Do have carrier blood in them because they are in part descendants of the old style carriers.

This is one reason why they are still commonly,

But erroneously called,

Carrier pigeons.

Homing pigeons were potentially being used for pigeon post in ancient Egypt by 1350 BCE.

Messages were tied around the legs of the pigeon,

Which was freed and could reach its original nest.

Pliny the Elder described pigeons used in a similar fashion as military messengers around the 1st century CE.

By the 19th century,

Homing pigeons were used extensively for military communications.

The sport of flying messenger pigeons was well established as early as 3,

000 years ago.

They were used to proclaim the winner of the ancient Olympics.

Messenger pigeons were used as early as 1150 in Baghdad,

And also later by Genghis Khan.

By 1167,

A regular service between Baghdad and Syria had been established by Sultan Nur ad-Din.

In Damietta,

By the mouth of the Nile,

The Spanish traveler Pedro de Afuera saw carrier pigeons for the first time in 1436,

Though he imagined that the birds made round trips out and back.

The Republic of Genoa equipped their system of watchtowers in the Mediterranean Sea with pigeon posts.

Tipu Sultan of Mysore,

1750-1799,

Also used messenger pigeons.

They returned to the Jamia Masjid mosque in Sri Rangapatna,

Which was his headquarters.

The pigeonholes may be seen in the mosque's minarets to this day.

In 1818,

A great pigeon race called the Cannonball Run took place at Brussels.

In 1860,

Paul Reuter,

Who later founded Reuter's press agency,

Used a fleet of over 45 pigeons to deliver news and stock prices between Brussels and Aachen,

The terminus of early telegraph lines.

The outcome of the 1815 Battle of Waterloo has often been claimed to have been delivered to London by pigeon,

But there is no evidence for this,

And it is very unlikely.

The pigeon post was rare until the 1820s.

During the Franco-Prussian War,

Pigeons were used to carry mail between besieged Paris and the French occupied territory.

In December 1870,

It took 10 hours for a pigeon carrying microfilms to fly from Perpignan to Brussels.

Historically,

Pigeons carried messages only one way to their home.

They had to be transported manually before another flight.

However,

By placing their food at one location and their home at another location,

Pigeons have been trained to fly back and forth up to twice a day reliably,

Covering round-trip flights up to 160 kilometers.

Their reliability has lent itself to occasional use on mail routes,

Such as the Great Barrier Pigeongram service established between the Auckland,

New Zealand suburb of Newton and Great Barrier Island in November 1897,

Possibly the first regular airmail service in the world.

The world's first airmail stamps were issued for the Great Barrier Pigeongram service from 1898 to 1908.

In the 19th century,

Newspapers sometimes used carrier pigeons.

To get news from Europe quicker,

Some New York City newspapers used carrier pigeons.

The distance from Europe to Halifax,

Nova Scotia is relatively short,

So reporters stationed themselves in Halifax,

Wrote the information received from incoming ships,

And put the messages in capsules attached to the legs of homing pigeons.

The birds would then fly to New York City where the information would be published.

Homing pigeons were still employed in the 21st century by certain remote police departments in Odisha state in eastern India to provide emergency communication services following natural disasters.

In March 2002,

It was announced that India's police pigeon service messenger system in Odisha was to be retired due to the expanded use of the internet.

The Taliban banned the keeping or use of pigeons,

Including racing pigeons in Afghanistan in the late 1990s.

To this day,

Pigeons are still entered into competitions.

Research has been performed with the intention of discovering how pigeons,

After being transported,

Can find their way back from distant places they have never visited before.

Most researchers believe that homing ability is based on a map and compass model,

With the compass feature allowing birds to orient,

And the map feature allowing birds to determine their location relative to a goal site,

Home loft.

While the compass mechanism appears to rely on the sun,

The map mechanism has been highly debated.

Some researchers believe that the map mechanism relies on the ability of birds to detect the earth's magnetic field.

A prominent theory is that the birds are able to detect a magnetic field to help them find their way home.

Scientific research previously suggested that on top of a pigeon's beak,

A large number of iron particles are found,

Which remain aligned to the earth's magnetic north,

Like a natural compass,

Thus acting as compass which helps pigeon in determining its home.

However,

A 2012 study disproved this theory,

Putting the field back on course to search for an explanation as to how animals detect magnetic fields.

A light-mediated mechanism that involves the eyes and is lateralized has been examined somewhat,

But developments have implicated the trigeminal nerve in magnetoreception.

Research by Floriano Papi,

Italy,

Early 1970s,

And more recent work,

Largely by Hans Walroff,

Suggests that pigeons also orient themselves using the spatial distribution of atmospheric odors,

Known as olfactory navigation.

Other research indicates that homing pigeons also navigate through visual landmarks by following familiar roads and other human-made features,

Making 90-degree turns and following habitual routes,

Much the same way that humans navigate.

Research by John Hangstrom of the U.

S.

Geological Survey suggests that homing pigeons use low-frequency infrasound to navigate.

Sound waves as low as 0.

1 Hz have been observed to disrupt or redirect pigeon navigation.

The pigeon ear,

Being far too small to interpret such a long wave,

Directs pigeons to fly in a circle when first taking air in order to mentally map such long infrasound waves.

Various experiments suggest that different breeds of homing pigeons rely on different cues to different extents.

Charles Walcott at Cornell University was able to demonstrate that wild pigeons from one loft were confused by a magnetic anomaly in the earth and had no effect on birds from another loft 1.

6 km away.

Other experiments have shown that altering the perceived time of day with artificial lighting or using air conditioning to eliminate odors in the pigeon's home roost affected the pigeon's ability to return home.

GPS tracing studies indicate that gravitational anomalies may play a role as well.

A message may be written on thin light paper,

Rolled into a small tube,

And attached to a messenger pigeon's leg.

They will only travel to one mentally marked point that they have identified as their home,

So pigeon posts can only work when the sender is actually holding the receiver's pigeon.

With training,

Pigeons can carry up to 75 grams on their backs.

As early as 1903,

The German apothecary Julius Neubrauner used carrier pigeons to both receive and deliver urgent medication.

In 1977,

A similar system of 30 carrier pigeons was set up for the transport of laboratory specimens between two English hospitals.

Every morning,

A basket with pigeons was taken from Plymouth General Hospital to Devonport Hospital.

The birds then delivered unbreakable vials back to Plymouth as needed.

The carrier pigeons became unnecessary in 1983 because of the closure of one of the hospitals.

In the 1980s,

A similar system existed between two French hospitals located in Granville and Alvranche.

Birds were used extensively during World War I.

One homing pigeon,

Cher Ami,

Was awarded the French Croix de Guerre for his heroic service in delivering 12 important messages,

Despite having been very badly injured.

During World War II,

The Irish Paddy,

The American G.

I.

Joe,

And the English Mary of Exeter all received the Dickin Medal.

They were among 32 pigeons to receive this award for their gallantry and bravery in saving human lives with their actions.

82 homing pigeons were dropped into the Netherlands with the first airborne division signals as part of the Operation Market Garden in World War II.

The pigeons' loft was located in London,

Which would have required them to fly 390 kilometers to deliver their messages.

Also in World War II,

Hundreds of homing pigeons with the Confidential Pigeon Service were airdropped into northwest Europe to serve as intelligence vectors for local resistance agents.

Birds played a vital part in the invasion of Normandy,

As radios could not be used for fear of vital information being intercepted by the enemy.

During the Second World War,

The use of pigeons for sending messages was highlighted in Britain by the Princess Elizabeth and Margaret as girl guides joining other guides sending messages to the World Chief Guide in 1943 as part of a campaign to raise money for homing pigeons.

A humorous IP over Avian Carriers,

RFC 1149,

Has an internet protocol for the transmission of messages via homing pigeon.

Originally intended as an April Fool's Day RFC entry,

This protocol was implemented and used once to transmit a message in Bergen,

Norway on the 28th of April 2001.

In September 2009,

A South African IT company based in Durban fitted an 11-month-old bird armed with a data-packed 4-gigabyte memory stick against the ADSL service from the country's biggest internet service provider,

Telkom.

The pigeon,

Winston,

Took an hour and eight minutes to carry the data 80 kilometers.

In all,

The data transfer took two hours,

Six minutes,

And a half minutes.

In all,

The data transfer took two hours,

Six minutes,

And 57 seconds,

The same amount of time it took to transfer four percent of the data over the ADSL.

Homing pigeons have been reported to be used as a smuggling technique,

Getting objects and narcotics across borders and into prisons.

For instance,

Between 2009 and 2015,

Pigeons have been reported to carry contraband items such as cell phones,

SIM cards,

Phone batteries,

And USB cords into prisons in the Brazilian state of Sao Paulo.

There have also been cases where homing pigeons were used to transport drugs into prisons.

Olfactory navigation is a hypothesis that proposes the uses of the sense of smell by pigeons,

In particular the male pigeon,

In navigating and homing.

There are two principal versions.

Poppy's mosaic model proposes that pigeons construct a map from the distribution of environmental odors within a radius of 70 to 100 kilometers.

Walrath's gradient theory overcomes the problem of distance limitation by proposing the existence of long-range,

Stable atmospheric odor gradients.

However,

The evidence to suggest that pigeons use an olfactory map in order to home is not conclusive.

Homing can be defined as the ability to return to a set point from potentially anywhere on Earth's surface,

Including destinations that are unfamiliar.

There are two criteria needed to coordinate this task.

A compass sense,

A sense of direction,

And a map sense,

A sense of location.

It is the ability to return from unfamiliar locations that pose the question of what sensory cues are used to determine locational information as well as directional information.

It has been proposed that the compass sense can be derived from a number of perspectives.

Magnetic orientation as a mechanism for directional sense was first put forward in the 19th century.

Equally,

The sun could be used as a compass in order to navigate home.

In 1972,

However,

Poppy and his contemporaries reported that anosmic pigeons were severely impaired in orientation and homing performance.

On the basis of the results,

The hypothesis of olfactory navigation was proposed.

Two models for olfactory navigation have been proposed,

Poppy's mosaic model and Walroth's gradient model.

Poppy's mosaic hypothesis advocates that pigeons construct a map from the distribution of environmental odors within a radius of 70 to 100 kilometers.

From this information,

It is possible to derive the home direction when encountering these odors at a release site.

An example of associated windborne sense would be pine forests,

Coastlines,

And pollution from cities.

It is argued that pigeons first learn to associate specific odors with particular locations during exercise and training flights.

This model has the advantage that it requires the bird only to detect the presence or absence of a range of odors.

Therefore,

Homing is viable only if the release sites are within a proximity that can provide reliable windborne cues,

Although Poppy argues the utilization of olfactory information obtained during the outward journey.

Walroth's gradient theory overcomes the problem of distance limitation by a different means.

It proposes the existence of long-range,

Stable,

Atmospheric odor gradients.

The foundation for this navigational map is a spatial representation in which two or more environmental odors have a particular intensity.

Odor gradient differs along dissimilar directional axes.

Therefore,

The pigeon can compare the intensity of the scent at a particular location to its concentration at the home loft.

This mechanism,

In principle,

Could operate over vast distances,

But would require the detection and interpretation of minute differences in odor concentration.

However,

A more poignant question is the existence of predictable odor gradients.

Meteorologists deny that odor gradients as required by this hypothesis exist in nature.

The olfactory navigation hypothesis states that pigeons learn an odor map by associating smells perceived at the home loft with the directions from which they are carried by winds.

Therefore,

Attempts to manipulate the development of that have involved changing the direction of wind,

Shielding birds from winds of a certain direction,

And exposing the pigeons to artificial odorants.

The predication is that the experimental pigeons should learn an altered map and thus when released they should fly according to their distorted perception.

Such an experiment was conducted where two groups of pigeons were reared and separate,

Although identical aviaries composed of bamboo.

Group one had air blown from the south containing olive oil and air from the north containing synthetic turpentine.

This was reversed for group two.

The pigeons were then released east of the loft.

Half had a drop of synthetic turpentine added to the bill while the others were given a drop of olive oil.

Pigeons from group one exposed to olive oil flew north,

Contrary to birds sentient to synthetic turpentine which flew south.

Consistent but reversed results were found in group two.

However,

It is important to note that there has been a failure to replicate these results in other countries,

Such as Germany,

Italy,

And the United States,

Even when considerable effort has been made to employ identical procedures.

Nevertheless,

Further experiments applied two different methods,

Namely the placement of fans near the home coop in order to reverse wind direction and usage of deflector lofts to shift the apparent direction of the wind by 90 degrees.

Deflector lofts comprised wooden or glass baffles which deflected wind course and therefore any signature odors.

Findings were that pigeons raised in such lofts oriented themselves with a magnitude of a 90 degree error,

Known as the deflector loft effect.

The wind-reversed experiments too exhibited results that favored the olfactory hypothesis,

With experimentals on average flying in the opposite direction of home,

While the controls took the correct flight path when released from the same site.

In replication of the deflector loft experiments,

Similar findings were produced,

Though when anosmic pigeons were employed,

They displayed the same degree of error and orientation as had previously been observed,

Therefore suggesting that the detection of odors may not have been associated with the deflector loft effect.

Indeed,

The flight directions could simply reflect a directional response to wind experienced in the loft or by other non-odorous factors,

Such as light reflection.

Researchers support these suggestions by noting the lack of highly developed nasal apparatus and associated brain functions in seeding birds such as pigeons.

It could be argued,

Therefore,

That pigeons are not dominated by olfactory landmarks when constructing a navigatory map.

Conflicting evidence,

However,

Was produced when pigeons were housed in open cages and exposed to a fan-produced air current carrying the scent of benzaldehyde.

When released with exposure only to the natural air during transport and at the release site,

Both experimentals and controls were homeward oriented,

Contrary if their response were simply to wind direction.

A consistent feature of the olfaction experiments is that anosmic pigeons that are released from familiar sites are essentially unaffected.

Perhaps a common fault of the olfactory mosaic and gradient model of olfactory navigation is that each model is oversimplistic and that they do not sufficiently take account of other cues that may be of importance.

The earth's magnetic field is a potential map cue as the field varies in both strength and direction over the earth's surface.

Manipulations of the ambient magnetic field are rather difficult,

Although Keaton,

1971,

And Ayole,

1984,

Did report that magnets caused disorientation in pigeons when they were released under total overcast.

This first indication for magnetic compass orientation in homing was later supported by other studies which reversed the field around the head of the pigeon using battery-operated coils.

Though the coils had little effect in clear conditions,

Their effect under overcast conditions was dependent on the direction of the current.

Another observation consistent with the idea of a geomagnetic map is the shift in the initial bearings of pigeons that occurs when the field increases during magnetic storms.

In magnetic anomalies too,

Pigeons are disoriented even under sunny conditions.

The predictable 15 degree movement per hour of the sun from east to west signifies its potential as a celestial compass.

This is possible providing the time of day is known and is achievable by birds due to their internal biological clock.

Experiments to test this hypothesis using the migratory European starling indicated that the direction of migration could be manipulated by reflecting the angle of the sun.

The effect was reproduced using homing pigeons.

Although this study is of value in demonstrating mechanisms other than olfaction and bird navigation,

It does not refer to pigeons.

The fundamental question of olfaction map sense in pigeons is,

Can they smell?

Available evidence suggests that pigeons lack highly developed nasal apparatus and associated brain functions,

Yet empirical evidence has shown that the homing ability of pigeons can be compromised by interfering with the olfactory environment.

However,

The variability and the effects of olfactory manipulations indicates that odors are not the sole cues on which navigation is based,

And that map sense appears to rely on a comparison of available cues.

Odor may still,

However,

Be one of many navigational factors playing a highly variable role,

Though physical limitations and inconsistent findings render the olfactory hypothesis questionable.

Magnetoreception is a sense which allows an organism to detect the earth's magnetic field.

Animals with this sense include some arthropods,

Mollusks,

And vertebrates,

Fish,

Amphibians,

Reptiles,

Birds,

And mammals.

The sense is mainly used for orientation and navigation,

But it may help some animals to form regional maps.

Experiments on migratory birds provide evidence that they make use of a cryptochrome protein in the eye,

Relying on the quantum-radical pair mechanism to perceive magnetic fields.

This effect is extremely sensitive to weak magnetic fields and readily disturbed by radiofrequency interference,

Unlike a conventional iron compass.

Birds have iron-containing materials in their upper beaks.

There is some evidence that this provides a magnetic sense,

Mediated by the trigeminal nerve,

But the mechanism is unknown.

Cartilaginous fish,

Including sharks and stingrays,

Can detect small variations in electric potential with their electroreceptive organs,

The ampullae of Lorenzini.

These appear to be able to detect magnetic fields by induction.

There is some evidence that these fish use magnetic fields in navigation.

Biologists have long wondered whether migrating animals,

Such as birds and sea turtles,

Have an inbuilt magnetic compass,

Enabling them to navigate using the earth's magnetic field.

Until late in the 20th century,

Evidence for this was essentially only behavioral.

Many experiments demonstrated that the animals could indeed derive information from the magnetic field around them,

But gave no indication of the mechanism.

In 1972,

Roswitha and Wolfgang Wiltzko showed that migratory birds responded to the direction and inclination dip of the magnetic field.

In 1977,

M.

M.

Walker and colleagues identified iron-based magnetite magnetoreceptors in the snouts of rainbow trout.

In 2003,

G.

Fleissner and colleagues found iron-based receptors in the upper beaks of homing pigeons,

Both seemingly connected to the animal's trigeminal nerve.

Research took a different direction in 2000,

However,

When Thorsten Ritz and colleagues suggested that a photoreceptor protein in the eye,

Cryptochrome,

Was a magnetoreceptor working at a molecular scale by quantum entanglement.

In animals,

The mechanism of magnetoreception is still under investigation.

Two main hypotheses are currently being discussed,

One proposing a quantum compass based on a radical pair mechanism,

The other postulating a more conventional iron-based magnetic compass with magnetite particles.

According to the first model,

Magnetoreception is possible via the radical pair mechanism,

Which is well established in spin chemistry.

The mechanism requires two molecules,

Each with unpaired electrons at a suitable distance from each other.

When these can exist in states either with their spin axes in the same direction or in opposite directions,

The molecules oscillate rapidly between the two states.

That oscillation is extremely sensitive to magnetic fields.

Because the earth's magnetic field is extremely weak at 0.

5 gauss,

The radical pair mechanism is currently the only credible way that the earth's magnetic field could cause chemical changes,

As opposed to the mechanical forces which would be detected via magnetic crystals acting like a compass needle.

In 1978,

Scholten and colleagues proposed that this was the mechanism of magnetoreception.

In 2000,

Scientists proposed that cryptochrome,

A flavoprotein in the rod cells in the eyes of birds,

Was the magnetic molecule behind this effect.

It is the only protein known to form photo-induced radical pairs in animals.

The function of cryptochrome varies by species,

But its mechanism is always the same.

Exposure to blue light excites an electron in a chromophore,

Which causes the formation of a radical pair whose electrons are quantum entangled,

Enabling the precision needed for magnetoreception.

Reviews

Thank you as ever for another splendidly fascinating and yet perfectly boring and definitely sleep-inducing episode 🕊️