How Do Early Warblers Survive A Cold Spell?

Yellow-rumped Warbler

After a week of unseasonably cold, wet weather, I headed down to the river to see how the warblers were doing.  I was amazed to see swarms of Yellow-rumped Warblers in downtown Durand, along RR 107 to Meridean and along the Buffalo River in Alma.

They were on the ground, on the water, in the shrubs, low on tree trunks in the flooded riverways, in the tree tops, at my suet feeders and back at home - on my windowsill. 

They were eating suet and hulled sunflower chips at my feeders, dead insects on my storm window frame, poison ivy berries along the roadsides - and emerging insects along the edges of the river.  Versatile eaters!

I spent an hour or so watching them eat insects along Rustic Road 107.  At first, I couldn't tell what they were eating.  The mosquito-sized little black flies were so small I could barely see them.   They swarmed my windshield, and after I powered down the window - they were all over me too. 

Fortunately they weren't the biting kind, but other than that, I didn't have a clue as to their identity.  So I took this photo.

Warbler food on my knuckle

When I got home, I went to www.bugguide.net thinking it would be awhile before anyone would get back to me with an identification.  Wrong.  I clicked "uplink" at 5:35pm and three minutes later, the identity was in an email in my inbox:   Male midge, likely tribe Tanytarsini.

According to the University of Minnesota Chironomidae Research Group,  there are over 1,000 species of non-biting midges - and over 300 species in Minnesota.  Plenty of insect protein for migrating Yellow-rumped Warblers.