Lunch comes right around two in the afternoon. Rock pigeons start gathering well ahead of time, perching in their dozens on the overhead power lines. Where our Kandewatte Lanes meet Pannipitiya Road opposite Buddhadasa Ground in Pelawatte sits a slightly raised traffic divider, site of the much-anticipated buffet. Six clay water dishes array themselves atop the red brick platform surface. Some yellow plastic boxes serve as bird baths.
Here comes the food! A gentleman rides up on a bicycle and begins flinging rice from a bucket onto the platform. Pigeons not already poised on the platform storm down from their perches to join the fluttering fray. Clamouring for position, some jump up flapping, then squeeze into gaps in the platform riot. There are other feeding times as well, starting at dawn when our trusty tuk driver Ajith distributes the eats, and periodically throughout the day as various fanciers arrive with treats.
I’m sure similar scenarios play out at spots across Colomboland. In the parking lot beneath Colpetty Market, hundreds of pigeons take turns on food waste dumped in an open space, then flap back up to perches on high walls, waiting ‘patiently’ while others have their go at the feast.
Rock pigeons have domesticated themselves since the dawn of humankind and especially since the onset of agriculture and towns. Beginning perhaps in South Asia some 300,000 years ago, rock pigeons pecked for crumbs in human caves and got themselves captured for food. They have proven themselves humanity’s top non-mammalian partner for hundreds of generations. They have assisted nearly every substantial army ever assembled up through the twentieth century and provided important gustatory sustenance for millions before mass production of domestic chicken.
Their role in long-distance messaging owes to astonishing navigational precision, combined with speedy flight and remarkable endurance. Messages attached to their tiny legs can be read by intended recipients when pigeons reach their homes. Trained racing pigeons today reach up to 100 kilometers per hour and 800 kilometers per day. Such flight capacities pivot on large and highly oxygenated breast muscles powering their wings.
Rock pigeons we see around us represent a semi-domesticated strain of the original wild rock pigeon. That bird found its home high on cliffs where predators could not reach their nestlings. Feeding themselves and their broods required prolonged sharp-eyed flights in search of seeds, grains, fruits and insects. Speed, endurance and ‘homing’ received evolutionary rewards. Pigeons carried these traits with them as they domesticated humans.
It’s helpful thinking of rock pigeons in four types: the original wild bird, which today still exists if at all only in the remotest locations; the fully domesticated bird, kept for messaging, food and ‘fancying’ (breeding for beauty and distinctiveness); the ‘feral’ bird, escaped from full domestication or descended from escapees, but still commensal with human settlements; and fourthly, descendants of partly self-domesticating birds from ancient times, which entered human commensalism without ever being fully kept. Since this fourth type is basically indistinguishable from the third, it can also be designated ‘feral’ if any such descendants still exist unmixed in ancestry from type three. It is of course ‘ferals,’ type three and perhaps four, that we see in our everyday lives. Categories one and four may no longer exist. These birds have interbred for long, long times. They are nothing if not gregarious.
Feral pigeons grew especially fond of cities where they could roost in increasingly tall buildings. With easy new food sources, their numbers grew and grew. They began to prove useful, conveying early alerts on disasters like a flood racing down the Nile. By and by they became key components in organized postal systems. Genghis Khan used pigeon post to administer his vast Asian empire.
At various times and places, pigeons have played a role in news services. Ancient Greece used them to carry tidings of Olympic Game winners. In the 1850s, Lanka’s Observer newspaper ran the ‘Pigeon Express’ between Colombo and Galle, carrying information on topics like events in the Crimean War.
Across Eurasia from China and India through the Mediterranean world, pigeons became a military asset, conveying intelligence, stratagems and outcomes. Until the electric telegraph, pigeons transmitted long-distance war messaging faster and more reliably than any other method. During World War I, they compensated extensively for the vulnerability and unreliability of telegraph, telephone and radio. For comparable reasons, militaries maintained substantial pigeon corps even through World War II.
Until recently, pigeon messages went only one way: towards home. The birds needed transport to a non-home location for delivering the next message. Around the dawn of the twentieth century, handlers discovered two-way delivery by separating home from food source. Tireless pigeons could make two round trips covering up to 160 total kilometers in a single day.
How do they do it? Their navigational feats obviously presuppose extraordinary sensory talents, combined with sophisticated brain processing. Research suggests that several capacities may come into play. We shall explore five of these here. It shall go without repeating that such capacities may not confine themselves to rock pigeons but may be shared with other animals, especially birds migrating long distances between breeding and wintering grounds: your Arctic Terns, your Bar-Tailed Godwits, Sooty Shearwaters and Lanka’s own Hueglin’s Gull, one of them named Manike.
Easiest to understand is visual acuity, perspective and memory. This would operate most strongly close to home. Pigeons absorb visual cues much the way we do when navigating. They even follow roads and make turns above intersections. But pigeon eyesight exceeds our own in navigational prowess. Eyes placed to the sides of their heads give them 340 degrees of visual sweep, which they can augment with simple head turns. Ability to see ultraviolet light, lacking in humans, provides extra information on landscape features like rock and vegetation formations. ‘Shape retention invariance,’ superior to ours, helps them recognize objects from any angle.
Farther from home, pigeon navigators rely on scent maps. While at home, they memorize patterns of wind-borne odours emanating from forests, water bodies and cities, carrying signature molecular compounds. Away from home, they sniff the local odour profile, register the ‘displacement’ from their home profile, and orient themselves homeward accordingly. Some scientists contend that they track and memorize scent changes during trans-
port from home then play it in reverse when homeward bound. Be that as it may, confirmation for scent-driven navigation comes from experiments with olfactory deprivation and wind manipulation.
Even farther out from home perhaps, pigeons navigate by sound. They can hear ‘infrasound,’ too low in pitch for human detection, as much as 400 times lower. Low in pitch, infrasound is conversely long in wavelength. Long-wavelength sound penetrates especially well over extended distance because it ‘diffracts’ around or past air and moisture particles that scatter shorter-wave sound. Shorter waves lie closer in scale to particles encountered and therefore tend to bounce off them and dissipate, whereas long waves slide around obstacles.
This holds as true in water as in air, which is why whales can use low-pitch, long-wavelength sound to communicate across ocean basins. What’s true of sound holds also for light. Red dawns and sunsets owe to sunlight traversing at a glancing angle through more atmosphere than when shining down directly at midday. Short-wavelength light towards the spectrum’s blue end gets scattered while long-wavelength red light continues to penetrate.
Naturally produced infrasound can help pigeons calculate the direction and distance of various earthscape features.
Natural infrasound emerges from wind flows through hills, wave action in water bodies, and currents upon and along continental shelves. Pigeons may hear wind over the Rockies from 2000 miles away. Breaking waves that trap air produce infrasound allowing detection of shorelines. Scientists use such infrasound to calculate ocean conditions through the size, frequency and location of distant waves.
Pigeons can hear whale song. (When sped up, whale song sounds remarkably like bird song. When slowed down, bird song sounds like whales.) Cracking ice, cascading rivers, atmospheric turbulence, and infrasound thunder from distant storms also fill the symphony. Modern civilization probably sharpens infrasound navigation at least sometimes. Human sources of infrasound include subways, motor vehicles, air conditioners and other machinery.
At greater distances from home and throughout journeys, pigeons deploy what scientists call a ‘sun compass.’ Nobody knows exactly how this works but here’s a stab at an explanation. An internal clock tells pigeons the time of day. They then establish the sun’s position while computing it against its varying positions through the year. They conjure its trajectory over the course of the day, especially its position at noon. They compare this information with recollection of the sun’s position and course at home as last seen so as to pick out their direction homeward as they fly. This process is especially valuable in discerning their latitude relative to home.
In addition to ultraviolet light, they also see polarised light to which we of course are blind. Earth’s atmosphere polarises sunlight. Patterns of polarisation rotate with the sun’s position. Their grasp of this helps pigeons calculate solar position even on cloudy days.
Finally, pigeons navigate with ‘magnetoreception,’ sensing and orienting themselves in Earth’s magnetic field. That
field consists of huge energy bands flowing between south and north magnetic poles, weak near the Equator and strong where they emerge or converge at the poles. This energy currently emerges at the south magnetic (positive) pole and submerges downward back into Earth’s magnetic iron core at the north (negative) magnetic pole. But this directional flow has reversed itself multiple times in Earth’s long history. Magnets do these things.
Magnetoreception garners experimental confirmation. Pigeons strapped with small magnets grow disoriented. Pigeons share magnetoreception not only with migratory birds but also with sea turtles, whales, sharks, lobsters, rodents, amphibians, snails and honeybees. They can detect the strength of the field, the angle of magnetic ‘dip’ towards a pole at different latitudes, and deflection east or west (longitude) due to iron-rich magnetic spots on the planet.
How pigeons do this at the sensory level remains under study. Two theories prevail, one that they ‘see’ the magnetic field, the other that they ‘hear’ it. ‘Seeing’ may involve ‘cryptochrome’ proteins in retinas, generating a shadowy magnetic map on top of normal vision. ‘Hearing’ may occur as the magnetic field induces electric currents in ear fluid.
Of course, only a tiny minority of rock pigeons today use much of the sophisticated navigational apparatus described here. With messaging superseded by technology these days, only racing pigeons routinely venture long-distance travel. We can wonder what happens to navigational talent in millions of pigeons always already home.