Recently I saw a couple dozen barn swallows following a hay cutter as it moved slowly through an alfalfa field. Those swallows were catching insects stirred into the air by the cutting machinery. They were entertaining to watch weaving swiftly among each other for several minutes without a single collision, due to their quick reflexes. I have seen this before in the fields of Lancaster County, Pennsylvania, but this time I was reminded of the birds I have seen following farm machinery of various kinds during spring and summer.
In March and April in this area, local farmers plow fields in preparation of planting corn, soybean and cigar tobacco. That turning the soil over is a dinner bell to gulls, mostly ring-bills this far inland, killdeer plovers, American crows, purple grackles and American robins that drop into the trenches behind the plows, often by the dozen, to catch earthworms and other invertebrates before those critters escape back into the soil.
Ring-billed gulls behind plows really put on a show. Groups of them at a time drop into the furrows behind the plows and compete vigorously for the creatures they can snare to eat, quickly gulping down what they catch. Meanwhile, as the plows keep moving ahead, more gulls drop into the trenches right behind those plows and ahead of the gulls already in the furrows to grab what critters they can. But within seconds, the gulls in the rear of the furrows fly up and ahead of the gulls that dropped into the plowed ground ahead of them, then drop to the ditches right behind the plows again. The result of that competition for food is a pinwheel affect of gulls in the rear of trenches flying over the ones in the furrows and dropping to the soil right behind the plows. That feathered pinwheel keeps rolling until all the birds are full of invertebrates.
Ring-bills and killdeer evolved in open habitats such as mud flats and beaches, so their being on a plowed field is expected. But grackles and robins developed as species in forest edges, making their entry in large, open fields quite an adaptation on their part. Grackles and robins spread over the plowed fields to seek invertebrate food, as well as dropping into the furrows after food.
American kestrels are a surprising bird species in plowed fields to ingest invertebrates. I first noticed that a few years ago when I saw a male kestrel drop from a roadside wire to a plowed field right behind the moving plow one afternoon early in April. With 16 power binoculars, I saw the kestrel pick up an earthworm and consume it. Kestrels mostly feed on mice and grasshoppers, so this was a mild surprise to me. But in nature, most anything is possible.
Swallows are as entertaining in their own way behind working farm machinery in summer as ring-billed gulls are in spring. Locally nesting swallow species involved in those, often mixed, gatherings behind farm equipment moving in the fields are barn and tree swallows, and purple martins, which are another kind of locally nesting swallows. By July, when hay and grain crops are harvested, these swallow species are done rearing offspring, and young and older birds alike are building up strength and fat reserves for the time when they drift south to escape the northern winter. Some of the feeding swallow flocks are of one species, but others are mixed. But as stated before, they are all entertaining following hay and grain cutters, rakes and balers across the fields, where they catch flying insects stirred up by that moving machinery.
Killdeer, crows, grackles and robins are also on those harvested fields to consume invertebrates. They don't follow the equipment, but spread over the fields, where vegetation is cut to the ground, to get food.
All these birds, particularly the gulls and swallows, are entertaining to see on Lancaster County fields. And it is inspiring to note these species are adaptable enough to take advantage of human-made habitats and activities for their own survival. Adapting is a key to success.
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