Polish Press Agency, The Polish Society for the Protection of Birds, and  Journal of Animal Ecology write about research of cooperative team of Population Ecology Lab and Charles University in Prague. The research is about avoiding competition in sibling species of birds.

http://naukawpolsce.pap.pl/aktualnosci/news,28896,konkurencja-w-stylu-slowika.html

https://otop.org.pl/2018/03/22/mechanizmy-unikania-konkurencji-u-blisko-spokrewnionych-gatunkow-mppl/

https://journalofanimalecology.wordpress.com/2018/03/21/how-do-birds-avoid-their-sibling-species-competitors/