<i><a href="//commons.wikimedia.org/wiki/Saxicola_rubicola" title="Saxicola rubicola">Saxicola rubicola</a></i>
Gross L.
CC BY 2.5
Gross L (2006) <a rel="nofollow" class="external text" href="http://biology.plosjournals.org/perlserv/?request=get-document&amp;doi=10.1371/journal.pbio.0040130">Remnants of the Past or Ready to Move? Resident Birds Display Migratory Restlessness.</a> PLoS Biol 4(4): e130 doi:10.1371/journal.pbio.0040130