Yellow-bellied flycatcher.
Rondeau Provincial Park, Aug 14, 2022. Identified with Merlin application. If I'm wrong let me know. Empidonax flaviventris. Yellow-bellied Flycatchers don't stick around on the breeding grounds for long. They have one of the shortest stays of any Neotropical migrant, often less than 70 days. source https://www.allaboutbirds.org/.../Yellow-bellied_Flycatcher