(CN) – For threatened piping plovers, engineered sandbars do not offer the same benefits as natural ones, a new study finds.
The report, published Wednesday in the journal The Condor: Ornithological Applications, examines whether engineered sandbars built along the Missouri River are effective substitutes for natural sandbars, the creation of which has been reduced along the river by the Gavins Point Dam on the Nebraska-South Dakota border.
Floods that hit the river in 2011 allowed a team of researchers to conduct a natural experiment demonstrating that, as nesting habitats for piping plovers, engineered sandbars simply do not stack up.
The team collected data downstream of the dam from 2005 to 2014, banding nearly 3,000 birds and monitoring more than 1,000 nests before and after the 2011 floods created large natural sandbars. More than 494 acres of engineered sandbars were built along the Missouri River between 2004 and 2009.
“I realized just how interesting of a natural experiment the flood provided us with when my advisor and I boated the entirety of the Gavins Point Reach prior to the 2012 field season,” said first author Kelsi Hunt, a research associate at Virginia Tech.
“The amount of sandbar habitat that the 2011 flood created was incredible to see. Where before there was just river, huge sandbars replaced it. Some of the sandbars it created were larger than city blocks and took hours to survey.”
Chick survival, nest success and total reproductive output all surged after the flood and remained high as the new natural sandbars began to age, even though the flood-created habitats did not receive the intensive predator management that had been performed on the engineered sandbars.
While piping plover populations nesting on engineered sandbars increased in the year following the habitat’s construction, there was not enough space for their growing numbers. The high population densities quickly put the plovers at greater risk from predators and decreased reproductive output.
Hunt hopes managers use the findings to develop better engineered habitats for sandbar-nesting birds, constructing more nesting space at one time and building new habitats near existing sandbars, which would help young birds find and colonize them.
“This paper presents a clear contrast in demographic rates of piping plovers in naturally created and human-restored habitats that can be used to compare and refine conservation strategies,” said Anne Hecht, piping plover recovery coordinator for the U.S. Fish and Wildlife Service. Hecht was not involved in the study.
“Although it focuses on Missouri River sandbars, it has important implications for conservation of piping plover habitat range-wide, as well as for other species experiencing disruption of habitat formation processes.”