Pigeon navigation RIN 11
A summary:
The RIN Conference spends a lot of time on pigeon navigation, with delegates coming from all over the world.
The leading players in this world are the Wilschkos from the Johann Wilfgang University Germany, M. Walker from the University of Auckland, and A. Gagliardo of the University of Pisa.
Overall, it was decided that pigeons use all the cues that they can to navigate by, just as humans would – navigation is difficult.
The Wilschko theory is that the birds have a magnetometer in their beak and a inclination compass in their eye to help find their way. An inclination compass is one that sees the world’s magnetic field as vertical at the poles and bending round to be parallel to at the equator. You use the change in angle to navigate by. The other clue is the changing intensity of the earth’s magnetic field which helps them navigate. Please note that this is not evenly distributed and some areas have very high intensity changes. The earth’s magnetic field is around 50 micro teslas ( 50,000 nano teslas) but it looks from experiments that pigeons appear to be able to sense changes of somewhere in the range 5-33 nano teslas about 1% of the earth’s magnetic field.
For instance, in the UK, this means that the vertical component of the Earth’s magnetic field from the tip of Scotland to Land’s End in Cornwall (approx. 50-58degrees North) goes from 4-48,000 nano teslas and the inclination from 65 – 72 degress.
I do not believe that these changes are fine enough to be used for pigeon navigation.
The other idea is that pigeons navigate using olfactory clues. The idea is that the pigeons build an olfactory map of their home loft and that, even over quite long distances, they can build up an olfactory map that directs them home. The birds for these experiments seemed to be released between 7 – 60 kms from their lofts with most experiments conducted with release between 30 – 60 kms.
There are experiments that “prove” that both systems are used by pigeons, but there is also much evidence that demolishes both theories. Some nice mathematical modelling was done by Ingo Schiffner who proved that pigeons must use at least four independent factors for their navigation.
In summary, I felt that compared to RIN08 this meeting was more open and that the delegates were less certain of any one main driver for pigeon navigation.
“There are experiments that “prove” that both systems are used by pigeons, but there is also much evidence that demolishes both theories.”
Comments from uqischif:
That’s harsh, you could also see it as a unification theory. It is plausible to assume that pigeons simply make use of both cues. Where priorities may shift depending on availability of these cues in the location where the experiments are conducted. Maybe pigeons in Pisa prefer olfactory cues, while those in Frankfurt may favour magnetic cues.