by Carl Strang
This week’s species dossier is for contrast. Though I have seen olive-sided flycatchers in several spring migration seasons in recent years, I have not been able to add anything significant to the first account I made in 2000. Prior to then, I had heard one calling its “quick three beers!” at Maple Grove Forest Preserve one spring in the mid-1980’s. I have never observed them in their North Woods breeding grounds, and I have not observed them during the fall migration.
25MY00. Willowbrook. Olive-sided flycatcher foraging from branches high in dead trees. Its bill is enormous, and its head large, giving it a distinctive look. This one was yellow in vent area. It was distinguished by the lack of an eye-ring and wing bars, along with the narrow light-colored channel between the dark sides of its breast. It never vocalized.
And that’s it. I have seen the species again at Willowbrook, at Fullersburg, and at Mayslake, but the story always has been the same. I limit the dossier to observations I have made myself. Of course, those observations are informed by what others have discovered, in this case that the large muscular head is an adaptation for crushing the hard exoskeletons of bees, wasps and other armored insects upon which this flycatcher feeds. Such prey become more active and abundant later in the season, so this species is one of the later migrants. I have never heard one call other than that one time in the 1980’s.