PHOENIX — After weeks of testimony in the water rights claim adjudication for the preservation of the San Pedro Riparian National Conservation Area (SPRNCA), the final day of hearings came May 16 with Leslie Arianna Brand, a well-credentialed avian research ecologist.
Under questioning by U.S. Department of Justice (DOJ) attorney Jenifer Najjar, Brand rebutted testimony given by Freeport Minerals, Inc., defense witness Steve Carothers, who had claimed many avian species would turn to the invasive tamarisk, also known as salt cedar, along the flood plain and mesquite bosques in the uplands to survive if the cottonwood and willow galleries died.
She called upon her experience of studying the San Pedro Riparian National Conservation Area (SPRNCA) bird species, the cottonwood and willow forest and the interaction of them with the flow of the San Pedro River.
Boquillas Ranch was her home base for around 12 months in a span of three years. Her time and studies on the riparian area provided the basis for her concerns for bird species, the cottonwood and willow canopies and river flow, which are all interrelated.
She took 2,700 surveys, with help from students, of all the birds seen or heard along all 40 miles of the SPRNCA.
Carothers only studied the southern section, she said.
“I was out there sunup to sundown walking the river,” Brand stated. “Having that kind of context adds to the reliability of my findings. There’s a whole different ecosystem in the northern SPRNCA.”
Brand said while some species may be able to find suitable habitat in the tamarisk stands and mesquite bosques, those that require nesting higher above ground would not.
The canopies offer a variety of heights to many nesting and migrant birds and so should be preserved by protecting the river flow.
Cottonwoods and willows sprout and grow along the floodplain of the San Pedro river and need water to be within 10 to 15 feet of their root systems.
“The statements Dr. Carothers made were overly narrow,” she added. “You have to look at avian richness, density, uniqueness and nesting success. In order to have the diversity of birds, you must have the cottonwood and willow forests and that means you have to have the water to support the most intact such forest in the U.S.”
The riparian area hosts one-third of all the birds in the U.S., she noted. “And, it’s two to three times higher in species richness than any other southwest river.”
Her studies showed tamarisk did not contribute to avian diversity, and if the trees declined, it would not impact any avian species.
She suggested birds would not be able to reproduce as well in tamarisk, or even in mesquite, as brown–headed cowbirds parasitize nests by laying eggs in the nest of another species.
The cowbird eggs hatch quicker than most species and so get most of the food. The larger nestlings are also known to nudge the other hatchlings out of the nests, reducing food competition.
“Birds are most productive in the canopy,” she emphasized. “Nests in canopies have the lowest parasitism rates.”
The canopies of the willows are the preferred nesting sites for the endangered southwestern willow flycatcher making it essential to maintain perennial river flow, Brand added.
As the river flow changes to intermittent or ephemeral, tamarisk takes over. Its roots go deeper, and it’s hard to kill. It quickly takes over what would be floodplain for the seedlings of willow and cottonwoods along the intermittent reaches, she explained.
“Mesquite is important, but it cannot replace the canopies. It’s a rare ecosystem and it needs both for the different avian species,” she said.
While answering questions from Michael Foy, attorney for the Salt River Project, which sides with the federal government, she stated the riparian would lose many species without the canopies and the perennial flows.
Water birds would be hardest hit with any decline, though insect-eating birds would also suffer from the lack of a food source.
After a few questions from Freeport Minerals, Inc., attorney Brian Heiserman, the trial concluded. A verdict is expected sometime next year.