I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Short-distance passerine migrants have two evolutionary origins. Those that have long-distance migrants in the same family, such as the common chiffchaff Phylloscopus collybita, are species of southern hemisphere origins that have progressively shortened their return migration to stay in the northern hemisphere."? 

Which birds have southern hemisphere origins?