Hypothetical superparamagnetic magnetometer in a pigeon’s upper beak probably does not work Petr Jandačka, Petr Alexa, Jaromír Pištora and Jana Trojková Eur. Phys. J. E, 36 4 (2013) 40 Published online: 23 April 2013 DOI: 10.1140/epje/i2013-13040-1