A SPRING RETENTION BASIN

      Two retention basins, one about an acre in size and the other around a quarter-acre, and both full of water in early May of 2026 when I visited them, lie at the bottom of four shallow slopes.  They were built to retain rain water and let that water drain away slowly, without eroding soil.  The slopes, totaling twelve acres, were planted to grass that is regularly mowed and a planted line of red maple trees on one slope and a planted row of white pines on another one.  Three weeping willow trees grow from the edges of the basins.  

     The grass helps retain soil and the trees add beauty to the lawn around the temporary pools of water.  Furthermore,  the twelve acres of short grass and the basins together were banquet tables and homes to a variety of birds and mammals when I visited them.

     Little groups of highly adaptable American robins, purple grackles and starlings were scattered across the lawn where they were consuming invertebrates from the grass and soil.  The robins might be starting to nest in the maples along one grassy slope.

      A pair each of yellow American goldfinches and pink and gray house finches were eating seeds from the seed heads of dandelion plants on the lawn around the mitigated impoundments.  Those small, pretty birds made the fluffy parachutes fly off dandelion seeds as they ate many of them.   

     About a dozen each of barn swallows and tree swallows dashed back and forth among their fellows low over the water, without collision with each other, to catch flying insects.  They were entertaining to see.  

     Five bachelor mallard ducks and six stately Canada geese rested on the shores of the larger basin.  Both these species ingest aquatic plants from the basins, and the geese also consume short grass from the lawn.  A couple each of mallards and Canadas could be incubating clutches of eggs in tiny patches of taller land plants near the retention basins.  

      A pair of killdeer plovers, which are a kind of shorebird that feeds on invertebrates on bare ground and short grass habitats near ponds and creeks, trotted along the narrow shorelines of the basins in their quest for invertebrates.  This pair might nest on the ground by these human-made impoundments.  

     A couple of little patches of cattails emerge from the shallows of the larger basin.  But cattails spread rapidly.  Already a couple of black, red-shouldered red-winged blackbird males repeatedly sing "kon-ga-reee" from the emerging cattails and willows while their beige and dark-striped mates search for places to build their grassy cradles interwoven among the cattails.

     I saw a muskrat swim across the bigger pond, then, suddenly, dive underwater.  Muskrats eat grass, cattails and other greenery in and around streams, ponds and basins.  And they dig tunnels into streambanks or build houses of heaps of grass and cattails in still waters.

     A row of red juniper trees occupies a corner of one grassy slope.  I saw a northern mockingbird among the junipers and a house cat on the ground just outside that patch of conifers.  The mocker eats the light-blue, berry-like fruits of the junipers through winter and into spring.  The cat hopes to ingest the mocker, and any other bird, plus mice, it finds in that row of junipers. 

     I returned to those retention basins and lawn two weeks later to see what was happening there.  The young white pines were sporting long, attractive growths of new needles at the tip of each limb.  The lawn was partially covered with white clover that was being visited by worker honey and bumble bees, busily sipping nectar.  Several grackles and a few robins were, again, on the lawn to ingest invertebrates.  

     A few red-winged blackbirds and six drake mallard ducks were along the shores of the larger impoundment.  The drakes were bachelors, while their mates are busily raising ducklings.  And I saw a pair of Canada geese and their four goslings and two broods of mallard ducklings, each with their mothers, along those same shorelines.

     Meanwhile, about a dozen tree swallows careened back and forth, low across both basins full of water, after flying insects to eat.  I have watched flocks of swallows swoop among their fellows in mid-air, and I never saw a collision among them.          

     All these adaptable creatures demonstrate how important even retention basins are to some species of wildlife.  And by planting patches of shrubbery and flowering plants, the numbers of species and individuals of wildlife will increase greatly.  Retention basins can be wonderful wildlife refuges, no matter how big or small they are.     

         


     

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