Bummer: CO2 is allegedly causing flowers to bloom earlier in spring, and that's allegedly bad for hummingbirds

Living on Earth: Citizens on the Watch for Hummingbirds

we’re discovering that the initial flowering is happening as many as two, two-and-a-half weeks ahead of when the hummingbirds arrive.

March 30, 2013: Marcia Davis: Northbound hummingbirds are better late than never » Knoxville News Sentinel

Freeze warnings. Winter weather advisories. Snow. Migrating ruby-throated hummingbirds have surely seen better springs than this one.

Tennessee’s cold, snowy, late March weather may be delaying the arrival of the earliest northbound ruby-throats. It’s not so much the effects of cold temperatures directly on the hummers. It’s the effects of cold temperatures on the hummers’ food supply. Small flying Insects take cover, hide, and remain inactive. Nectar-bearing flowering plants are nipped in the bud. Flowers freeze. Blossoming of future flowers is delayed. Hummers may resort to eating sap at sapsucker wells in trees.