News Life Pigeon navigation finding called off-course Biological ‘sensor’ in beaks may instead be immune system cells Share this:FacebookTwitterPocketRedditPrintEmail By Susan Milius April 11, 2012 at 5:21 pm This article is only available to Science News subscribers. Subscribers, enter your e-mail address to access our archives. Client key* E-mail* Log in Not a subscriber? Science News is a nonprofit. Support us by subscribing now. Subscribe