28 June 2013

Homing Pigeon Navigation

Welcome back. Let me guess. Whenever you see a pigeon carrying a Save me! or Save the castle! message in a movie or TV show, you wonder: How does that pigeon know where to go?

I hope you haven’t wasted too much time wondering, because only the pigeons know for sure. But the latest findings by a US Geological Survey researcher may have the answer.

Homing Pigeons

Before I started this topic, I knew only that when I coo’ed, which I do quite well for a human, the doves on my deck and the pigeons on the street always flew away seemingly offended.

City pigeons on the streets
of Old San Juan, Puerto Rico.
(www.rachelphilipson.com)

Now I know that pigeons and doves are pretty much the same animal (Columbidae) and that “homing” pigeons are just a domestic variety of Rock pigeons (Columba livia), being the same species as city pigeons that color our statues. A homing pigeon that totes notes may be called a “carrier” or “messenger” pigeon.

Noah’s dove I knew, but I had no idea that pigeons were exhibiting their homing skills in Egypt in 2900 BCE. Later, they were delivering messages throughout the Middle East, in ancient China, India and elsewhere. In 2350 BCE, for example, human messengers in what’s now Iraq carried homing pigeons to signal if their capture was imminent. In ancient Greece, pigeons announced the Olympic results.

Though used as food and pets and for racing and show, the employment of pigeons as messengers, particularly in war time, is cited into the 21st Century. An area in India ended its Police Pigeon Service messenger system in 2002.

Finding its Way Home

Once a homing pigeon is trained, which is done in part by releasing the bird from different directions, at increasing distances from its home loft, the bird will normally find its way home from hundreds of miles away. Accomplishing this journey requires a sense of relative locations as would be portrayed on a map and a mastery of directions as might be gotten with a compass.

Prior research has largely established that, for its compass, pigeons make use of the sun and possibly other celestial bodies and--via the iron particles in their beaks--the Earth’s magnetic field. What serves as a pigeon’s map has been the question.

The birds appear to rely on visual landmarks as you or I might though that wouldn’t work for unseen areas. It’s also been suggested that smell might play a role. The latest finding, proposed by the same USGS researcher in 2000, covers all the map bases and would explain why homing pigeons regularly get confused or lost when released from some locations and under some conditions:

The birds might be using sound; to be exact, infrasound--very low frequency sound waves beyond human hearing. (You might want to read or re-read my blog post, Bird Talk, in which I describe infrasound and research that found peacocks communicate in the infrasound.)

Acoustic Maps

Ocean wave interactions cause the Earth to emit a constant seismic noise (microseism) in the infrasound. This background noise, detectable nearly everywhere, is modified by topography (mountains, valleys) and may thus provide the pigeons’ map.

To expand this concept of “acoustic avian maps,” the researcher employed acoustic ray-tracing using daily meteorological profiles. He was able to account for all considered cases of pigeons failing to reach home as well as anomalous flight patterns.

Acoustic maps would explain documented cases of bird confusion when the infrasonic signal between the home loft and release point was blocked or when there was interference caused by the shockwave of the supersonic airplane Concord.

Wrap Up

Further testing is needed to confirm and better understand this potential breakthrough in long-distance navigation, yet the notion that sound provides the key is fascinating. Do other animals that hear infrasound--whales for example--make use of the signal for more than communication? Can we make use of these signals? Thanks for stopping by.

P.S.

- Latest (2013) paper in Journal of Experimental Biology: jeb.biologists.org/content/216/4/687.abstract?sid=2290d93a-9686-4960-8923-cd6951c9e782
- Older (2000) paper in Journal of Experimental Biology: jeb.biologists.org/content/203/7/1103.abstract?sid=14bd5775-9694-467d-99e4-7c1508022c31
- Reviews of 2013 findings:
www.dvice.com/2013-1-31/homing-pigeons-may-navigate-maps-infrasound
www.livescience.com/26714-how-homing-pigeons-navigate.html
www.bbc.co.uk/news/science-environment-21262170
- Homing pigeons, including history:
suite101.com/article/columbidae-doves-and-pigeons-a30515
suite101.com/article/all-about-homing-pigeons-a73655
www.mediahistory.umn.edu/archive/pigeonpost.html
en.wikipedia.org/wiki/Homing_pigeon
- Website of International Federation (American Homing Pigeon Fanciers Inc): www.ifpigeon.com/
 

P.P.S.

You forgot, didn't you? There's still time to enter the blog contests.
-Writing: Describe your Personal Best, deadline Monday, 1 July,
link: Personal Best Writing Contest
-Photography: Depict “Personal Best,” deadline Sunday, 30 June,
link: Personal Best Photo Contest

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