A few kinds of summering birds that I have watched getting food in southeastern Pennsylvania benefit from lawn mowing in suburban areas and hay cutting in croplands.

These species are adaptable, common in much of North America, and entertaining to watch as they snap up invertebrates stirred into the air by machinery mowing grass or hay.

And, most interestingly, these birds have learned to associate mowers of various kinds with suddenly available food.

American robins run and stop, run and stop over short-grass lawns and watch and listen for invertebrates at grass’s root level when they stop.

Mowers moving over lawns flush out flying insects, particularly froghoppers and small, brown moths, which the robins see and grab with their beaks. Mowers make it easier for robins to get the food they already prey upon, and in greater abundance.

Gray catbirds roam over lawns in search of food much the way robins do. Catbirds, however, nest in thickets of shrubbery and vines along woodland edges and streambanks and in older suburban areas.

I chuckle when mowing grass and see a catbird perched on the edge of shrubbery to watch the mower’s progress across the lawn.

When the catbird spots a moth rising from the grass before the mower, it zips low across our lawn, seizes the insect in its bill right in front of the mower, and flips away with it to a perch to swallow its victim and watch for more.

Barn swallows, tree swallows, chimney swifts, and purple martins, which are another kind of swallow, are built similarly for catching flying insects in midair. Examples of convergent evolution, they are all small, speedy, and maneuverable in flight and have large mouths to engulf their prey.

Entertaining to watch, swallows and swifts swoop swiftly over hayfields after flying insects stirred out of pretty clover and alfalfa fields by hay mowers.

Beautiful poetry in motion, the many swallows and swifts weave in and out among their fellows without collision, ever. And that collection of graceful, airborne birds moves up and down the hayfields close behind and to the sides of the mowers.

When full of insects, the swallows line up on roadside wires to rest, digest their meals, socialize, and preen their feathers. And when hungry again, off they go to follow the mowers across the hay fields to catch more flying insects.

These adaptable birds all get food more easily by following mowing machines on lawns and in fields. And we are entertained by their food-gathering activities on those human-made habitats, right at home.


Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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