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  • Flood Control District transforms dirt site into a birding haven

    Dec 09, 2021 | Read More News
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    By Mary Reynolds
    Pima County Communications

    In 2016, the Regional Flood Control District began restoring a 15-acre dirt site in the Rillito River Park near North Columbus Boulevard. A recent walk through the reseeded area, with waist-high grasses and other native plants, demonstrates the success of the restoration. 

     sparrow patch
     The 15-acre site in the Rillito River near North Columbus Boulevard now hosts a wide
    variety of birds and other native animals and plants.
    Flood Control had used the site to deposit sediment removed from the Rillito River as part of a maintenance project to restore floodwater capacity for public safety. By placing the 500,000 tons of sediment locally, RFCD saved taxpayers roughly $2 million in transportation and dumping expenses. 

    Unbeknownst to the District at the start of the project, the sediment-deposit area was a birding hotspot known as the “Columbus Weed Patch,” a dense, weedy-looking mix of monsoon-driven wildflowers and mostly nonnative grasses. Dickcissel and clay-colored sparrows, both regionally uncommon, frequented the seedy bonanza during most winters.

    Flood Control had plans to restore the area. However, upon learning of the birding site, the District partnered with the Tucson Audubon Society to develop an enhanced plan, including 58 native plant species, to best support wildlife previously seen at the site. 

    Flood Control installed rain-harvesting earthworks and applied two specialized native seed mixes tailored to the upland thickets and flood-prone riparian bosque (forest) areas. The seed mixes were mostly grasses and small perennials — such as bristlegrass, globe mallow, Parry penstemon, Trans-Pecos thimblehead, needle grama, Rothrock’s grama, dogweed, Arizona poppy, cinchweed and chia — that typically flourish without need for irrigation.

    The District added irrigation lines along the south and east edges of the project to sustain new plantings of young desert willow and other native trees and shrubs adjacent to The Chuck Huckelberry Loop.

    Next, Flood Control worked with Natural Resources, Parks and Recreation’s Loop maintenance crews to eliminate nonnative vegetation as well as create a habitat for lizards. Without the pre-existing grasses and shrubs, native lizards had no place to hide from predators. Loop maintenance workers brought in larger mesquite and palo verde tree trimmings to create numerous brush piles that became safe refuges for lizards and other wildlife, including birds.
     brush pile
    Brush piles created from tree trimmings provided refuges for lizards and other wildlife,
    including birds, until other plants could grow in the area.

    “It was a way to jump-start and fast-forward a natural succession and habitat restoration process,” explained Jennifer Becker, an environmental planning manager with the District.

    “After we replanted in 2016, there were a couple of very dry years, so the vegetation struggled to come back. But with this year’s heavy monsoon, everything looks great.” 

    She described this year’s monsoon effects on the area: “The thick blanket of sediment on the overbank acts like a sponge to retain rainwater and lengthen the growing season. The re-directed urban runoff and recent Rillito Creek flood events supported exceptional tree and shrub growth along the north edge of the project area.”

    Rainfall totals on July 23 and Aug. 14, 2021, were close to what scientists call a 100-year flood event — a flood that statistically has a 1% chance of occurring any given year, or once every 100 years.

    Jonathan Horst of Tucson Audubon pointed to the human-made channel and explained: “Neighborhood storm runoff is captured throughout the rainy seasons, providing water to the plants. It’s floodplain vegetation, but it’s getting flow as if it was a wash.”

    Becker added that after the summer rains, “There were also native toads breeding here.”

    Today, the area looks like a golden meadow, with plenty of grasses starting to go to seed. This bird buffet will continue through the winter. 

    Birds you might see feasting on grass seeds this winter are lesser goldfinches, Lazuli buntings and numerous grass-eating sparrows: Rufous-winged sparrow, Vesper sparrows, black-throated sparrows, Lincoln’s sparrow, Brewer’s sparrows, lark sparrows and white-crowned Sparrows. Other Sonoran Desert species identified in the replanted area include Cooper’s hawks, Gambel’s quails, Anna’s hummingbirds, Bell’s vireos, Vermilion flycatchers and Peregrine falcons. Birders often log their finds on the eBird site created by the Cornell University Lab of Ornithology.

    It’s no longer a weed patch, according to Becker, “because native plants replaced nonnative weed species and many sparrows find a home here.

    “We now call it ‘The Sparrow Patch.’”