© 2020, The Author(s). The attached document (embargoed until 10/01/2021) is an author produced version of a paper published in JOURNAL OF AVIAN BIOLOGY uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.