Why Do Hummingbirds Fly Close To The Grass?

Q: In our local park there are several hummingbirds that are always flying a couple of feet above the grass. What are they doing? 

A: We think of them as nectar feeders but hummingbirds also enjoy eating
small insects. It’s how they get protein, fats, and fiber. Aphids, gnats,
mosquitoes, and spiders are favorites. They sometimes hang out near the sap
wells made by sapsucker woodpeckers to pluck sap-feeding insects. To
enhance hummingbird feeding, make a slurry of fruit, mashed banana and a
bit of cake batter, mixing it to a consistency of thick brownie dough. Spread
the slurry directly on tree branches or trunks. Insects will come to feed on the
slurry and hummingbirds will feed on the swarm.