BG Biogeosciences BG Biogeosciences 1726-4189 Copernicus Publications Göttingen, Germany 10.5194/bg-10-6929-2013 Ratios among atmospheric trace gases together with winds imply exploitable information for bird navigation: a model elucidating experimental results Wallraff H. G. 1 Max Planck Institute for Ornithology, 82319 Seewiesen/Starnberg, Germany 04 11 2013 10 11 6929 6943 Copyright: © 2013 H. G. Wallraff 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/articles/10/6929/2013/bg-10-6929-2013.html The full text article is available as a PDF file from https://bg.copernicus.org/articles/10/6929/2013/bg-10-6929-2013.pdf

A model of avian goal-oriented navigation is described that is based on two empirical findings building a bridge from ornithology to atmospheric chemistry. (1) To orient their courses homeward from distant unfamiliar areas, homing pigeons require long-term exposure to undisturbed winds at the home site and olfactory access to the environmental air at home and abroad. (2) Above Germany, ratios among some atmospheric trace gases vary along differently oriented spatial gradients as well as depending on wind direction. The model emulates finding (1) by utilising the analysed air samples on which finding (2) is based. Starting with an available set of 46 omnipresent compounds, virtual pigeons determine the profile of relative weights among them at each of 96 sites regularly distributed around a central home site within a radius of 200 km and compare this profile with corresponding profiles determined at home under varying wind conditions. Referring to particular similarities and dissimilarities depending on home-wind direction, they try to estimate, at each site, the compass direction they should fly in order to approach home. To make the model work, an iterative algorithm imitates evolution by modifying sensitivity to the individual compounds stepwise at random. In the course of thousands of trial-and-error steps it gradually improves homeward orientation by selecting smaller sets of most useful and optimally weighted substances from whose proportional configurations at home and abroad it finally derives navigational performances similar to those accomplished by real pigeons. It is concluded that the dynamic chemical atmosphere most likely contains sufficient spatial information for home-finding over hundreds of kilometres of unfamiliar terrain. The underlying chemo-atmospheric processes remain to be clarified.

 References Able, K. P.: The debate over olfactory navigation by homing pigeons, J. Exp. Biol., 199, 121–124, 1996. Able, K. P.: The concepts and terminology of bird navigation, J. Avian Biol., 32, 174–183, 2000. Batschelet, E.: Circular statistics in biology. Academic Press, London, 1981. Becker, J. and van Raden, H.: Meteorologische Gesichtspunkte zur olfaktorischen Navigationshypothese, J. Ornithol., 127, 1–8, 1986. Boström, J. E., Åkesson, S., and Alerstam, T.: Where on earth can animals use a geomagnetic bi-coordinate map for navigation?, Ecography, 35, 1039–1047, 2012. Gagliardo, A.: Forty years of olfactory navigation in birds, J. Exp. Biol., 216, 2165–2171, 2013. Gagliardo, A., Bried, J., Lambardi, P., Luschi, P., Wikelski, M., and Bonadonna, F.: Oceanic navigation in Cory's shearwaters: evidence for a crucial role of olfactory cues for homing after displacement, J. Exp. Biol., 216, 2798–2805, 2013. Ioalè, P., Nozzolini, M., and Papi, F.: Homing pigeons do extract directional information from olfactory stimuli, Behav. Ecol. Sociobiol., 26, 301–305, 1990. Kramer, G.: Experiments on bird orientation, Ibis, 94, 265–285, 1952. Merkel, F. W. and Wiltschko, W.: Magnetismus und Richtungsfinden zugunruhiger Rotkehlchen (<i>Erithacus rubecula</i>), Vogelwarte, 23, 71–77, 1965. Papi, F.: Pigeon navigation: solved problems and open questions, Monit. Zool. Ital. (N. S.), 20, 471–517, 1986. Papi, F.: Pigeons use olfactory cues to navigate, Ethol. Ecol. Evol., 1, 219–231, 1989. Papi, F.: Olfactory navigation, in: Orientation in birds, edited by: Berthold, P., Birkhäuser, Basel, 52–85, 1991. Papi, F., Fiore, L., Fiaschi, V., and Benvenuti, S.: The influence of olfactory nerve section on the homing capacity of carrier pigeons, Monit. Zool. Ital. (N.S.), 5, 265–267, 1971. Papi, F., Ioalè, P., Fiaschi, V., Benvenuti, S., and Baldaccini, N. E.: Olfactory navigation of pigeons: the effect of treatment with odorous air currents, J. Comp. Physiol., 94, 187–193, 1974. Schmidt-Koenig, K.: Über die Entfernung als Parameter bei der Anfangsorientierung der Brieftaube, Z. vergl. Physiol., 52, 33–55, 1966. Schmidt-Koenig, K.: Entfernung und Heimkehrverhalten der Brieftaube, Z. vergl. Physiol., 68, 39–48, 1970. Waldvogel, J. A.: Olfactory navigation in homing pigeons: are the current models atmospherically realistic?, Auk, 104, 369–379, 1987. Waldvogel, J. A.: Olfactory orientation in birds, Curr. Ornithol., 6, 269–321, 1989. Wallraff, H. G.: Simulated navigation based on assumed gradients of atmospheric trace gases (models on pigeon homing, part 2), J. Theor. Biol., 138, 11–528, 1989. Wallraff, H. G.: Navigation by homing pigeons, Ethol. Ecol. Evol., 2, 81–115, 1990. Wallraff, H. G.: Seven theses on pigeon homing deduced from empirical findings, J. Exp. Biol., 199, 105–111, 1996. Wallraff, H. G.: Simulated navigation based on observed gradients of atmospheric trace gases (models on pigeon homing, part 3), J. Theor. Biol., 205, 133–145, 2000. Wallraff, H. G.: Navigation by homing pigeons: updated perspective, Ethol. Ecol. Evol., 13, 1–48, 2001. Wallraff, H. G.: Avian olfactory navigation: its empirical foundation and conceptual state, Anim. Behav., 67, 189–204, 2004. Wallraff, H. G.: Avian navigation: pigeon homing as a paradigm, Springer, Berlin, 2005a. Wallraff, H. G.: Beyond familiar landmarks and integrated routes: goal-oriented navigation by birds, Connect. Sci, 17, 91–106, 2005b. Wallraff, H. G.: Pigeon homing as a model case of goal-oriented navigation, in: Encyclopedia of animal behavior, vol 2, edited by: Breed, M. D. and Moore, J., Academic Press, Oxford, 713–722, 2010. Wallraff, H. G. and Andreae, M. O.: Spatial gradients in ratios of atmospheric trace gases: a study stimulated by experiments on bird navigation, Tellus, 52, 1138–1157, 2000. Williams, J.: Organic trace gases in the atmosphere: an overview, Environ. Chem., 1, 125–136, 2004.